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The neuronal basis of bimanual coordination: recent neurophysiological evidence and functional models
Abstract
Recent physiological studies of the neuronal processes underlying bimanual movements provide new tests for earlier functional models of bimanual coordination. The recently acquired data address three conceptual areas: the generalized motor program (GMP), intermanual crosstalk and dynamic systems models. To varying degrees, each of these concepts has aspects that can be reconciled with experimental evidence. The idea of a GMP is supported by the demonstration of abstract neuronal motor codes, e.g. bimanual-specific activity in motor cortex. The crosstalk model is consistent with the facts that hand-specific coding also exists and that interactions occur between the motor commands for each arm. Uncrossed efferent projections may underlie crosstalk on an executional level. Dynamic interhemispheric interactions through the corpus callosum may provide a high-level link at the parametric programming level, allowing flexible coupling and de-coupling. Flexible neuronal interactions could also underlie adaptive large-scale systems dynamics that can be formalized within the dynamic systems theory approach. The correspondence of identified neuronal processes with functions of abstract models encourages the development of realistic computational models that can predict bimanual behavior on the basis of neuronal activity.
... Such types of bimanual movements consist of a high level of similarity in neural activity between the contralateral muscles, and the activation of ipsilateral neural signals is congruent (Kelso, 1984;Marteniuk et al., 1984;Kagerer et al., 2003;Maki et al., 2008). Neural crosstalk connecting homologous muscles causes strong bilateral interaction between these muscles (e.g., Cohen, 1971;Kelso, 1984;Cardoso de Oliveira, 2002;Swinnen, 2002). ...
... Additionally, it is suggested that asymmetrical bimanual motor tasks which require a more differentiated role for each arm interfere more than bimanual movements where each arm is moved along the same trajectory (e.g., Marteniuk et al., 1984;Summers et al., 1993;Franz et al., 1996;Swinnen, 2002). The neural activity in bilateral motor tasks with different task parameters (e.g., trajectories, amplitude, and frequency) can, therefore, cause negative neural crosstalk (in terms of motor performance) between the homologous primary and supplementary motor cortex and muscles, where the neural activity between the limbs is not similar (Marteniuk et al., 1984;Cardoso de Oliveira, 2002). In this type of neural crosstalk, the mirrored neural activity from the contralateral arm conflicts with an appropriate neural activity associated with the specific motor task in the contralateral arm and, thus, causes bilateral interference (Marteniuk et al., 1984;Summers et al., 1993;Cardoso de Oliveira, 2002;Kagerer et al., 2003). ...
... The neural activity in bilateral motor tasks with different task parameters (e.g., trajectories, amplitude, and frequency) can, therefore, cause negative neural crosstalk (in terms of motor performance) between the homologous primary and supplementary motor cortex and muscles, where the neural activity between the limbs is not similar (Marteniuk et al., 1984;Cardoso de Oliveira, 2002). In this type of neural crosstalk, the mirrored neural activity from the contralateral arm conflicts with an appropriate neural activity associated with the specific motor task in the contralateral arm and, thus, causes bilateral interference (Marteniuk et al., 1984;Summers et al., 1993;Cardoso de Oliveira, 2002;Kagerer et al., 2003). Therefore, because of a stronger bilateral interaction and crosstalk between homologous compared to non-homologous brain areas and muscles, it can be expected that the potential bilateral interference is higher for homologous muscle groups compared to non-homologous muscle groups. ...
Performance of bimanual motor actions requires coordinated and integrated bilateral communication, but in some bimanual tasks, neural interactions and crosstalk might cause bilateral interference. The level of interference probably depends on the proportions of bilateral interneurons connecting homologous areas of the motor cortex in the two hemispheres. The neuromuscular system for proximal muscles has a higher number of bilateral interneurons connecting homologous areas of the motor cortex compared to distal muscles. Based on the differences in neurophysiological organization for proximal vs. distal effectors in the upper extremities, the purpose of the present experiment was to evaluate how the level of bilateral interference depends on whether the bilateral interference task is performed with homologous or non-homologous effectors as the primary task. Fourteen participants first performed a unilateral primary motor task with the dominant arm with (1) proximal and (2) distal controlled joysticks. Performance in the unilateral condition with the dominant arm was compared to the same effector’s performance when two different bilateral interference tasks were performed simultaneously with the non-dominant arm. The two different bilateral interference tasks were subdivided into (1) homologous and (2) non-homologous effectors. The results showed a significant decrease in performance for both proximal and distal controlled joysticks, and this effect was independent of whether the bilateral interference tasks were introduced with homologous or non-homologous effectors. The overall performance decrease as a result of bilateral interference was larger for proximal compared to distal controlled joysticks. Furthermore, a proximal bilateral interference caused a larger performance decrement independent of whether the primary motor task was controlled by a proximal or distal joystick. A novel finding was that the distal joystick performance equally interfered with either homologous (distal bilateral interference) or non-homologous (proximal bilateral interference) interference tasks performed simultaneously. The results indicate that the proximal–distal distinction is an important organismic constraint on motor control and for understanding bilateral communication and interference in general and, in particular, how bilateral interference caused by homologous vs. non-homologous effectors impacts motor performance for proximal and distal effectors. The results seem to map neuroanatomical and neurophysiological differences for these effectors.
... Neural crosstalk occurs when both hemispheres send commands to the contralateral limb via the crossed corticospinal pathways while concurrently sending a mirror image command to the ipsilateral limb via the uncrossed corticospinal pathways (Cardoso de Oliveira 2002;Cattaert et al. 1999). This ipsilateral influence may alter the activation of the involved muscle (e.g., Cattaert et al. 1999;Cardoso de Oliveira 2002;Swinnen 2002) likely adding to or subtracting from the contralateral muscle activation depending on whether the command is excitatory or inhibitory (e.g., Barral et al. 2006Barral et al. , 2010Walter and Swinnen 1990). ...
... Neural crosstalk occurs when both hemispheres send commands to the contralateral limb via the crossed corticospinal pathways while concurrently sending a mirror image command to the ipsilateral limb via the uncrossed corticospinal pathways (Cardoso de Oliveira 2002;Cattaert et al. 1999). This ipsilateral influence may alter the activation of the involved muscle (e.g., Cattaert et al. 1999;Cardoso de Oliveira 2002;Swinnen 2002) likely adding to or subtracting from the contralateral muscle activation depending on whether the command is excitatory or inhibitory (e.g., Barral et al. 2006Barral et al. , 2010Walter and Swinnen 1990). During a bimanual task that requires the limbs to produce disparate actions (e.g., 30°, 1:2), ongoing interference from conflicting information or partial intermingling of the signals controlling the two limbs may render performance of the task difficult (e.g., Cardoso de Oliveira 2002; Kagerer et al. 2003;Maki et al. 2008;Marteniuk et al. 1984). ...
... As such, one inherent constraint that may, in part, explain the performance and stability differences between the two groups is neural crosstalk. It has been hypothesized that in-phase coordination patterns using homologous muscles are facilitated when contralateral and ipsilateral signals are integrated (Cardoso de Oliveira 2002;Kagerer et al. 2003;Marteniuk et al. 1984). The behavioral results of the current investigation support such a possibility. ...
The current investigation was designed to examine the influence of inherent and incidental constraints on the stability characteristics associated with bimanual and social coordination. Individual participants (N = 9) and pairs of participants (N = 18, 9 pairs) were required to rhythmically coordinate patterns of isometric forces in 1:1 in-phase and 1:2 multi-frequency patterns by exerting force with their right and left limbs. Lissajous information was provided to guide performance. Participants performed 13 practice trials and 1 test trial per pattern. On the test trial, muscle activity from the triceps brachii muscles of each arm was recorded. EMG–EMG coherence between the two EMG signals was calculated using wavelet coherence. The behavioral data indicated that individual participants performed the 1:1 in-phase pattern more accurately and with less variability than paired participants. The EMG coherence analysis indicated significantly higher coherence for individual participants than for the paired participants during the 1:1 in-phase pattern, whereas no differences were observed between groups for the 1:2 coordination pattern. The results of the current investigation support the notion that neural crosstalk can stabilize 1:1 in-phase coordination when contralateral and ipsilateral signals are integrated via the neuromuscular linkage between two effectors.
... However, it is possible that the lower values of error and variability during the in-phase coordination pattern compared with all the other patterns were due to a stabilizing effect occurring via the neuro-muscular linkage (e.g. neural crosstalk) and/or to a destabilizing effect for all the other phase relations (Cardoso de Oliveira 2002;Kagerer et al. 2003: Marteniuk et al. 1984 rather than factors associated with the feedback (Lissajous) provided. As such, assessing coordination performance and stability under the same conditions (metronome/Lissajous) while removing the neuro-muscular linkage between the component oscillators (limbs) (i.e., interpersonal coordination) may provide additional insights relative to perceptual/ attentional and neuro-muscular constraints on coordination dynamics. ...
... According to the neural crosstalk model, two independent motor plans exist for each limb and some fraction of the force command for one limb is transmitted to the contralateral limb (Cattaert et al. 1999). Because neural crosstalk conveys the same information to both limbs, it is believed that in-phase coordination patterns using homologous muscles are facilitated when the contralateral and ipsilateral signals are integrated (Cardoso de Oliveira 2002;Kagerer et al. 2003;Marteniuk et al. 1984). The results of the current investigation support such a possibility. ...
... When performing relative phase patterns other than 0°, the commands to each limb are often in conflict (Summers et al. 1993). Performance of a 90° relative phase pattern, for example, may suffer from ongoing interference believed to result from the conflicting information or intermingling of the signals controlling the two effectors (e.g., Cardoso de Oliveira 2002;Kagerer et al. 2003: Maki et al. 2008: Marteniuk et al. 1984. Indeed, performance of relative phase patterns between 30° and 150° with metronomes in the current investigation was quite difficult, as indicated by the high error and variability. ...
Both intrapersonal and interpersonal coordination dynamics have traditionally been investigated using relative phase patterns of in-phase (ϕ = 0°) and/or anti-phase (ϕ = 180°). Numerous investigations have demonstrated that coordination tasks that require other relative phase patterns (e.g., 90°) are difficult or near impossible to perform without extended practice. Recent findings, however, have demonstrated that an individual can produce a wide range of intrapersonal bimanual patterns within a few minutes of practice when provided integrated feedback. The present experiment was designed to directly compare intra- and interpersonal coordination performance and variability when provided Lissajous feedback or pacing metronome. Single participants (N = 12) and pairs of participants (N = 24, 12 pairs) were required to produce relative phase patterns between 0° and 180° in 30° increments using either pacing metronomes or Lissajous displays. The Lissajous displays involved a goal template and a cursor providing integrated feedback regarding the position of the two effectors. The results indicated both single and pairs of participants could effectively produce a large range of coordination patterns that typically act as repellers after only 6 min of practice when provided integrated feedback. However, single participants performed the in-phase coordination pattern more accurately and with less variability than paired participants, regardless of the feedback condition. These results suggest an advantage for intrapersonal coordination when performing in-phase coordination, possibly due to the stabilizing effect occurring via the neuro-muscular linkage between effectors.
... Homologous muscles of two limbs are used for symmetric movements, which are performed into mirror directions along the body-midline, whereas non-homologous muscles are used for parallel movements which are performed into spatially equal directions (Swinnen, Jardin, Meulenbroek, Dounskaia & Hofkens-Van den Brandt, 1997). Cardoso de Oliveira (2002) explains the interdependency of bimanual movements with 'crosstalk' of the signals in both hemispheres. In symmetric movements the interhemispheric interactions in the corpus callosum coincide which makes symmetric movements easier to perform than non-symmetric movements (Cardoso de Oliveira, 2002). ...
... Cardoso de Oliveira (2002) explains the interdependency of bimanual movements with 'crosstalk' of the signals in both hemispheres. In symmetric movements the interhemispheric interactions in the corpus callosum coincide which makes symmetric movements easier to perform than non-symmetric movements (Cardoso de Oliveira, 2002). ...
It is assumed that imagined and executed actions are based on similar mechanisms because they take approximately the same amount of time, follow the same motor principles, and involve similar brain areas. In motor imagery and motor execution, internal models (e.g. forward models) are supposed to predict the action consequences on the actor and the environment. The predictive mechanisms in motor imagery were investigated in two series of experiments. In Series 1, cognitive factors and bimanual principles influenced motor imagery and motor execution similarly. In Series 2, deviations from optimal performance were observed in motor imagery and motor execution. However, predictions showed fewer deviations from optimal performance than actual performance, regardless whether predictions were based on motor imagery or motor execution. Further, the action consequences were similarly influenced by expertise in motor imagery and motor execution. The findings strengthen the assumption of similar mechanisms in motor imagery and motor execution. Most likely, a simulation of the action takes place in motor imagery that predicts the action consequences. This prediction may be based on forward models. The observed results enhance the understanding of the mechanisms of motor imagery and contribute to a solid theoretical and empirical basis for applications of motor imagery in mental practice.
... To further complicate performance and learning of bimanual tasks, the control signals to each limb may be susceptible to the effects of neural crosstalk [25,26]. Neural crosstalk occurs during bimanual tasks when a mirror image of the control signals sent to one muscle group is also dispatched to the homologous muscles of the contralateral limb [27,28] via crossed and uncrossed corticospinal pathways [27,29]. Research has indicated much stronger correlations between interhemispheric motor cortical areas, consistent with simultaneous activation in both hemispheres, during in-phase than anti-phase coordination [29,30]. ...
... Neural crosstalk occurs during bimanual tasks when a mirror image of the control signals sent to one muscle group is also dispatched to the homologous muscles of the contralateral limb [27,28] via crossed and uncrossed corticospinal pathways [27,29]. Research has indicated much stronger correlations between interhemispheric motor cortical areas, consistent with simultaneous activation in both hemispheres, during in-phase than anti-phase coordination [29,30]. It is believed this correlated activity between the hemispheres is the neural basis of neural crosstalk between the limbs [28]. ...
An experiment was designed to determine whether accuracy constraints can influence how unimanual and bimanual motor sequences are produced and learned. The accuracy requirements of the task were manipulated using principles derived from Fitts' Law to create relatively low (ID = 3) and high (ID = 5) accuracy demands. Right-limb dominant participants (N = 28, age = 21.9 yrs; 15 females and 13 males) were required to produce unimanual left, unimanual right or bimanual movement sequences using elbow extension and flexion movements to hit a series of illuminated targets. The targets were illuminated in a repeating sequence of 16 elements. Participants performed 20 practice trials. Thirty minutes following the practice trials participants performed a retention test. Element duration (time interval between target hits) and segment harmonicity (hesitations/adjustments in movement pattern) were calculated. The results indicate longer element duration and lower harmonicity values (more adjustments) when the task required higher accuracy demands (ID = 5) compared to low accuracy demands (ID = 3). Element duration was shorter and harmonicity was higher at ID = 5 for both unimanual groups than the bimanual group. However, element duration was shorter and harmonicity was higher at ID = 3 for the bimanual group than for both unimanual groups. These results indicate that the accuracy demands of the task can influence both performance and learning of motor sequences and suggest differences between unimanual and bimanual motor sequence learning. It appears there is a bimanual advantage for tasks with lower accuracy demands whereas performance is more accurate with unimanual performance, regardless of limb, with higher accuracy demands. These results are consistent with recent research indicating that accuracy requirements change the control processes for bimanual performance differently than for unimanual tasks.
... Our hypothesis was that asymmetric loading conditions and asymmetric arm configurations might affect, respectively, the accuracy of lifting the two hands at the same height and/or applying bilaterally equal isometric forces. In fact, in mirror symmetric condition the CNS could simply solve the task of guiding the two hands toward the common goal by transmitting the same motor commands to both sides of the body [43][44][45]. Conversely, in the presence of different sensory feedback from the two arms, the CNS must take into account this difference and compensate for it, producing different bilateral motor commands for achieving the same common goal. We wonder whether the CNS might not account correctly for the mismatch on the sensory inputs between the two limbs when pursuing a bilateral equal force or position goal; the differences in performance among task conditions would highlight this effect. ...
... Specifically, in symmetric conditions (LC 1 and LC 2 ) both hands had higher target-variable-error when holding heavier than lighter weights. In symmetric conditions the two hands received the same additional feedback (i.e., the position of the other hand) and since the variability associated with force/ heaviness perception is known to be higher for higher forces/weights [44,45], we expected the two hands having higher variability when holding heavier weights. In the two asymmetric conditions (LC 3 and LC 4 ), the two hands received a different feedback in dependence of the weight they were holding. ...
Background:
Several daily living activities require people to coordinate the motion and the force produced by both arms, using their position sense and sense of effort. However, to date, the interaction in bimanual tasks has not been extensively investigated.
Methods:
We focused on bimanual tasks where subjects were required: (Experiment 1) to move their hands until reaching the same position - equal hand position implied identical arm configurations in joint space - under different loading conditions;(Experiment 2) to produce the same amount of isometric force by pushing upward, with their hands placed in symmetric or asymmetric positions. The arm motions and forces required for accomplishing these tasks were in the vertical direction. We enrolled a healthy population of 20 subjects for Experiment 1 and 25 for Experiment 2. Our primary outcome was the systematic difference between the two hands at the end of each trial in terms of position for Experiment 1 and force for Experiment 2. In both experiments using repeated measure ANOVA we evaluated the effect of each specific condition, namely loading in the former case and hand configuration in the latter.
Results:
In the first experiment, the difference between the hands' positions was greater when they were concurrently loaded with different weights. Conversely, in the second experiment, when subjects were asked to exert equal forces with both arms, the systematic difference between left and right force was not influenced by symmetric or asymmetric arm configurations, but by the position of the left hand, regardless of the right hand position. The performance was better when the left hand was in the higher position.
Conclusions:
The experiments report the reciprocal interaction between position sense and sense of effort inbimanual tasks performed by healthy subjects. Apart for the intrinsic interest for a better understanding of basic sensorimotor processes, the results are also relevant to clinical applications, for defining functional evaluation and rehabilitative protocols for people with neurological diseases or conditions that impair the ability to sense and control concurrently position and force.
... Neural crosstalk is believed to result when a mirror image of the command(s) sent to one muscle group is also dispatched to the homologous muscles of the contralateral limb (e.g., Cattaert et al. 1999 andSwinnen 2002). This happens when both hemispheres send commands to the contralateral limb via the crossed corticospinal pathways while concurrently sending the same command to the ipsilateral limb via the uncrossed corticospinal pathways (Cardoso de Oliveira 2002;Cattaert et al. 1999). When the commands to both limbs are congruent (e.g., both limbs are producing the same action), interference is not likely to occur (Maki et al. 2008) and may even stabilize task performance when the contralateral and ipsilateral signals are integrated (e.g., Cardoso de Oliveira 2002 and Kagerer et al. 2003). ...
... Neural crosstalk may influence actions at both the execution and planning levels (e.g., Cardoso de Oliveira 2002; Heuer et al. , 2002Marteniuk et al. 1984;Spijkers et al. 1997). Interference at the execution level is associated with motor output from efferent motor commands whereas interference at the planning level is associated with the specification process prior to the execution of the task goal (Cardoso de Oliveira 2002;Heuer et al. , 2002Marteniuk et al. 1984;Spijkers et al. 1997). Reaction time tasks are commonly used as an indirect measure to examine influences at the planning level (e.g., Diedrichsen et al. 2001;Hazeltine et al. 2003;Hoyer and Bastian 2013;Obhi and Goodale 2005). ...
Two experiments were designed to determine response biases resulting from production of force in the contralateral limb and head position. Participants were required to react with one limb while tracking a sinewave template by generating a pattern of force defined by the sinewave with the contralateral limb or watching a cursor move through the sinewave. In Experiment 1, participants had to react with their right or left limb while their head was in a neutral position. In Experiment 2, participants had to react with their left limb while their head was turned 60° to the left or right. A color change of the waveform signaled participants to produce an isometric contraction with the reacting limb. Reaction time was calculated as the time interval between the color change of the waveform and the initiation of the response. The results indicated mean reaction time for the left limb was significantly influenced by force production in the right limb. During left limb reactions, reaction time was faster for trials in which both limbs initiated force simultaneously as compared to trials in which the left limb initiated force while the right limb was producing force. Mean reaction time for the right limb was not influenced by force production in the contralateral limb. The results are consistent with the notion that crosstalk can influence the time required to react to stimuli but this influence occurs at the point of force initiation and is asymmetric in nature with the dominant limb exerting a stronger influence on the non-dominant limb than vice versa. However, we did not find a similar effect for head position via the tonic neck response.
... Healthy subjects are able to generate and maintain self-paced rhythmic movement sequences and to synchronize them with external cues [3,4], engaging different neural pathways. Also, bimanual coordination, which is the ability to use both hands at the same time in a controlled and organized manner, is an important component of motor hand function and is possible since both sides of the brain communicate and share information with each other [5,6]. ...
... Recent studies based on quantitative assessment of finger opposition movements in patients with neurological diseases showed performance impairments with respect to healthy controls [1][2][3][4][5][6]. In addition, a measure of fine hand motor function has shown to be fundamental when investigating the effects of a motor rehabilitation protocol aiming at improving or maintaining fine movements and coordination skills, allowing comparisons between sessions and groups [7]. ...
Background
Finger opposition movements are the basis of many daily living activities and are essential in general for manipulating objects; an engineered glove quantitatively assessing motor performance during sequences of finger opposition movements has been shown to be useful to provide reliable measures of finger motor impairment, even subtle, in subjects affected by neurological diseases. However, the obtained behavioral parameters lack published reference values.
Objective
To determine mean values for different motor behavioral parameters describing the strategy adopted by healthy people in performing repeated sequences of finger opposition movements, examining associations with gender and age.
Methods
Normative values for finger motor performance parameters were obtained on a sample of 255 healthy volunteers executing sequences of finger-to-thumb opposition movements, stratified by gender and over a wide range of ages. Touch duration, inter-tapping interval, movement rate, correct sequences (%), movements in advance compared with a metronome (%) and inter-hand interval were assessed.
Results
Increasing age resulted in decreased movement speed, advance movements with respect to a cue, correctness of sequences, and bimanual coordination.
No significant performance differences were found between male and female subjects except for the duration of the finger touch, the interval between two successive touches and their ratio.
Conclusions
We report age- and gender-specific normal mean values and ranges for different parameters objectively describing the performance of finger opposition movement sequences, which may serve as useful references for clinicians to identify possible deficits in subjects affected by diseases altering fine hand motor skills.
... Similarly, some portion of the muscle activation generated in the right hemisphere for the left limb is diverted to the right limb. This occurs when both hemispheres send commands to the contralateral limb via the crossed corticospinal pathways while concurrently sending the same command to the ipsilateral limb via the uncrossed corticospinal pathways (Cardoso de Oliveira 2002;Cattaert et al. 1999). As such, each limb is primarily controlled by the contralateral hemisphere; however, there is also an ipsilateral influence that is integrated with the contralateral command. ...
... As such, each limb is primarily controlled by the contralateral hemisphere; however, there is also an ipsilateral influence that is integrated with the contralateral command. This ipsilateral influence is believed to alter the activation of the involved muscles (e.g., Cattaert et al. 1999;Cardoso de Oliveira 2002;Swinnen 2002). In a 1:1 in-phase bimanual coordination task, neural crosstalk is not likely to cause interference between the limbs, because the commands to both limbs are congruent (Maki et al. 2008). ...
Unimanual (left and right limbs) and bimanual (in-phase) reciprocal aiming tasks were tested to determine if the control processes used to perform the unimanual aiming tasks were also present in bimanual aiming tasks. Participants were asked to move a cursor as quickly and accurately as possible between the two targets presented in a Lissajous feedback display. The size of the targets created indexes of difficulty (ID) of 3, 4, 5, and 6 and the position of the targets created bimanual and unimanual conditions. The results indicated that, as ID increased, the end-effectors’ motion gradually switched from a cyclical to a more discrete motion for both unimanual and bimanual aiming tasks. However, the transition in control processes (i.e., the transition between cyclical and more discrete motions) tended to occur at a lower ID for the bimanual than the unimanual aiming tasks. Results also indicated that at ID6, bimanual aiming tasks were performed slower, more variable, and right limb dwelled at the targets longer than in the unimanual aiming task. No differences in performance were detected between the unimanual (left and right) and bimanual conditions at IDs 3–5. In terms of bimanual coordination, increasing the accuracy requirement resulted in decreased relative phase bias, but not more stable coupling between the two limbs.
... As detailed above, two main factors could contribute to altering bimanual coordination pattern stability with aging. The first factor is a change in the coupling strength between the components, which would occur as a result of structural changes of brain connectivity and functional changes of neural crosstalk in the aging brain [23,24] , including time delays of information transmission [25] , reduction of attentional capacity [4,26] , and alteration in proprioceptive and visual information processing [5] . In the modeling of bimanual coordination dynamics by Haken et al. [18] , inference with regard to changes in coupling strength is usually made on the basis of the magnitude of relative phase variability [19,27] . ...
... Indeed, given the equivalent spatial constraints, a difference in pattern stability between the 2 groups might likely result from inherent (e.g. alteration of neural connections or time delays) [23,25] rather than strategic changes in coupling strength and/or enhancement of neural noise with aging. ...
... In symmetric 1:1 in-phase bimanual coordination task neural crosstalk is not likely to cause interference between the limbs because the commands to both limbs are congruent (Maki et al. 2008). In fact, it is believed that 1:1 in-phase task is stabilized when complementary contralateral and ipsilateral signals are integrated (e.g., Cardoso de Oliveira 2002; Kagerer et al. 2003; Maki et al. 2008; Marteniuk et al. 1984). However , during multi-frequency tasks the commands to each limb are often in conflict (Summers et al. 1993b). ...
... However , during multi-frequency tasks the commands to each limb are often in conflict (Summers et al. 1993b). Thus, performance of multi-frequency coordination patterns can suffer from ongoing interference believed to result from the conflicting information or partial intermingling of signals controlling the two limbs (e.g., Cardoso de Oliveira 2002; Kagerer et al. 2003; Maki et al. 2008; Marteniuk et al. 1984). Indeed, Kennedy et al. (2015b) compared the bimanual production of 1:1 in-phase and 1:2 force patterns (Experiment 3). ...
Results from a recent experiment (Kennedy et al. in Exp Brain Res 233:181-195, 2015) indicated consistent and identifiable distortion of the left limb forces that could be attributable to the production of right limb forces during a multi-frequency bimanual force task. However, distortions in the forces produced by the right limb that could be attributable to the production of force in the left limb were not observed. The present experiment was designed to replicate this finding and determine whether the influence of force produced by one limb on the contralateral limb is the result of the limb assigned the faster frequency on the limb performing the slower frequency or a bias associated with limb dominance. Participants (N = 10) were required to rhythmically coordinate a pattern of isometric forces in a 1:1, 1:2, or 2:1 coordination pattern. The 1:2 task required the right limb to perform the faster rhythm, while the 2:1 task required the left limb to perform the faster rhythm. The 1:1 task was used as a control. Participants performed 13 practice trials and 1 test trial per task. Lissajous displays were provided to guide performance. If the limb assigned the faster frequency was responsible for the distortions observed in the contralateral limb, it was hypothesized that distortions would only be observed in the force trace of the limb producing the slower pattern of force. If a bias associated with limb dominance was responsible for the distortions observed in the contralateral limb, it was hypothesized that in right-limb-dominant participants the right limb would influence the left limb, regardless of limb assignment. Replicating the results of the previous experiment, only distortions in the left limb were observed in the 1:2 coordination task that could be attributed to the production of force by the right limb. However, identifiable distortions were observed in the force produced by both the left and right limb in the 2:1 coordination task. Observed distortions in the left limb, when assigned the faster rhythm indicated that the source of interference is not limited to limb assignment but also a function of limb dominance.
... This way, our study aimed at analyzing theta band coherence after 48 hours of hand immobilization. The electrode derivations were selected through qEEG in different brain regions: the frontal region, due to its relationship with the pre-motor and pre-frontal cortexes, which are functionally related to action creation and voluntary control [23] and to executive functions [24]; the central region, which represents motor act execution [25,26]; the parietal region, because of its relationship with sensorimotor integration [23,27] and the temporal region, since it represents the secondary motor areas [28]. Therefore, our study hypothesized that the hand immobilization period provokes changes in the inter and intra-hemispheric coherence in the frontal, central, parietal and temporal regions, as well as providing information about the neural mechanisms involved in the motor act execution. ...
... Theta band coherence increased in the frontal region, especially for the F3/Fz derivations. Other studies have demonstrated that the pre-motor and pre-frontal cortexes are related to action creation and voluntary control and to executive functions [28,31], and that theta activity occurs during that behavior which demands planning updating for the motor act, according to the received sensory information [5,35]. This way, due to the fact of the coherence analysis presenting evidence of the coupling between cortical areas during motor task execution [21,22], our findings demonstrate that, in order for the individual to execute the task, greater coupling between these areas was needed for the planning and motor response to the stimulus, which then demanded greater joint action of such cortical regions [36]. ...
Many different factors can temporarily or permanently impair movement and impairs cortical organization, e.g. hand immobilization. Such changes have been widely studied using electroencephalography. Within this context, we have investigated the immobilization effects through the theta band coherence analysis, in order to find out whether the immobilization period causes any changes in the inter and intra-hemispheric coherence within the cerebral cortex, as well as to observe whether the theta band provides any information about the neural mechanisms involved during the motor act. We analyzed the cortical changes that occurred after 48 hours of hand immobilization. The theta band coherence was study through electroencephalography in 30 healthy subjects, divided into two groups (control and experimental). Within both groups, the subjects executed a task involving flexion and extension of the index finger, before and after 48 hours. The experimental group, however, was actually submitted to hand immobilization. We were able to observe an increase in the coupling within the experimental group in the frontal, parietal and temporal regions, and a decrease in the motor area. In order to execute manual tasks after some time of movement restriction, greater coherence is present in areas related to attention, movement preparation and sensorimotor integration processes. These results may contribute to a detailed assessment of involved neurophysiological mechanism in motor act execution.
... Neural crosstalk occurs when both hemispheres send motor commands to the contralateral limb via the crossed corticospinal pathways while simultaneously sending a mirror image of the motor command to the ipsilateral limb via the uncrossed corticospinal pathways (Cattaert et al., 1999;Cardoso de Oliveira, 2002). This ipsilateral influence may alter the activation of the involved muscle (Cattaert et al., 1999;Swinnen, 2002) resulting in increased or decreased contralateral muscle activation depending on whether the motor command is excitatory or inhibitory (e.g., Barral et al., 2006Barral et al., , 2010. ...
Many of the activities associated with spaceflight require individuals to coordinate actions between the limbs (e.g., controlling a rover, landing a spacecraft). However, research investigating the influence of gravity on bimanual coordination has been limited. The current experiment was designed to determine an individual’s ability to adapt to altered-gravity when performing a complex bimanual force coordination task, and to identify constraints that influence coordination dynamics in altered-gravity. A tilt table was used to simulate gravity on Earth (90° head-up tilt (HUT)) and microgravity (6° head-down tilt (HDT)). Right limb dominant participants (N=12) were required to produce 1:1 in-phase and 1:2 multi-frequency force patterns. Lissajous information was provided to guide performance. Participants performed 14, 20 s trials at 90° HUT (Earth). Following a 30-minute rest period, participants performed two retention trials (Earth) followed by two transfer trials in simulated microgravity (6° HDT) for each coordination pattern. Results indicated that participants were able to transfer their training performance during the Earth condition to the microgravity condition with no additional training. No differences between gravity conditions for measures associated with timing (interpeak interval ratio, phase angle slope ratio) were observed. Despite the effective timing of the force pulses, however, there were differences in measures associated with force production (peak force, mean force, STD of force). The results of this study suggest that Lissajous displays may help counteract manual control decrements observed during microgravity. Future work should continue to explore constraints that can facilitate or interfere with bimanual control performance in altered-gravity environments.
... The improvement of speed in the presence of interference may be driven by a two-way facilitating influence of bimanual movements that result in a faster and more automated drawing due to activation of callosal fibers that have a key role in bimanual coordination (Andres et al., 1999;Cardoso de Oliveira, 2002). Another reason for this increase of speed during interference could be that 67% of children played a musical instrument; and therefore, they had a higher level of bimanual coordination as a result of the enhanced development of motor cortex controlling for both hands (Amunts et al., 1997). ...
Drawing and handwriting are fine motor skills acquired during childhood. We analyzed the development of laterality by comparing the performance of the dominant with the nondominant hand and the effect of bimanual interference in kinematic hand movement parameters (speed, automation, variability, and pressure). Healthy subjects ( n = 187, 6–18 years) performed drawing tasks with both hands on a digitizing tablet followed by performance in the presence of an interfering task of the nondominant hand. Age correlated positively with speed, automation, and pressure, and negatively with variability for both hands. As task complexity increased, differences between both hands were less pronounced. Playing an instrument had a positive effect on the nondominant hand. Speed and automation showed a strong association with lateralization. Bimanual interference was associated with an increase of speed and variability. Maturation of hand laterality and the extent of bimanual interference in fine motor tasks are age-dependent processes.
... Among other aspects, this work revealed limitations of the classical mechanical view that "Newton Rules Biology" [35]. Later research was to identify the neurophysiological basis of these phenomena in human brain recordings, both empirically (e.g., [36][37][38][39]) and theoretically [40][41][42][43][44][45][46]. ...
Coordination is a ubiquitous feature of all living things. It occurs by virtue of informational coupling among component parts and processes and can be quite specific (as when cells in the brain resonate to signals in the environment) or nonspecific (as when simple diffusion creates a source–sink dynamic for gene networks). Existing theoretical models of coordination—from bacteria to brains to social groups—typically focus on systems with very large numbers of elements (N→∞) or systems with only a few elements coupled together (typically N = 2). Though sharing a common inspiration in Nature’s propensity to generate dynamic patterns, both approaches have proceeded largely independent of each other. Ideally, one would like a theory that applies to phenomena observed on all scales. Recent experimental research by Mengsen Zhang and colleagues on intermediate-sized ensembles (in between the few and the many) proves to be the key to uniting large- and small-scale theories of coordination. Disorder–order transitions, multistability, order–order phase transitions, and especially metastability are shown to figure prominently on multiple levels of description, suggestive of a basic Coordination Dynamics that operates on all scales. This unified coordination dynamics turns out to be a marriage of two well-known models of large- and small-scale coordination: the former based on statistical mechanics (Kuramoto) and the latter based on the concepts of Synergetics and nonlinear dynamics (extended Haken–Kelso–Bunz or HKB). We show that models of the many and the few, previously quite unconnected, are thereby unified in a single formulation. The research has led to novel topological methods to handle the higher-dimensional dynamics of coordination in complex systems and has implications not only for understanding coordination but also for the design of (biorhythm inspired) computers.
... X biomechanical effort X coordination as a cognitive burden (see brain injury studies) 5 X coordinating movement of multiple muscles around multiple joints on different limbs ü size relationships (GETTING-BIGGER) ü action of one character on an object or another character (as in FLATTER) ü reciprocal action (as in LOOK-AT-EACH-OTHER) ü Signers are used to paying those costs ü Each method is a kind of over-specification ü This redundancy enhances comprehensibility and resolves ambiguity 6 ...
... Certainly, people draw on paper with one hand and even purportedly ambidextrous artists, such as Adolph Menzel, use only one hand at a time (Singer, 1910, reported on in Gurney, 2011. Furthermore, moving two hands rather than one poses a cognitive burden (as shown in studies of brain injuries, disorders and pathologies; see citations in de Oliveira, 2002). Plus, there are computational costs of coordinating the movement of multiple muscles around multiple joints on different limbs, costs that critically involve the cerebellum and the dorsal premotor cortex (Debaere, Wenderoth, Sunaert, Van Hecke, & Swinnen, 2004). ...
In sign languages, the task of communicating a shape involves drawing in the air with one moving hand (Method One) or two (Method Two). Since the movement path is iconic, method choice might be based on the shape. In the present studies we aimed to determine whether geometric properties motivate method choice. In a study of 17 deaf signers from six countries, the strongest predictors of method choice were whether the shape has any curved edges (Method One), and whether the shape is symmetrical across the Y‐axis (Method Two), where the default was Method One. In a second study of ASL dictionary entries for which the movement path of the sign is iconic of an entity's shape, the same predictors surfaced. These tendencies are captured in the Lexical Drawing Principle, which is coherent with biological constraints on movement in general. Drawing in the air with two hands, however, is costly, both cognitively and biomechanically. Furthermore, it distinguishes signers from non‐signers, who draw shapes with only one hand. Signers assume this extra cost in the lexicon because of the enhanced iconicity the possibility of two hands offers; they assume it in drawing shapes in the air because they apply the same linguistic principle they use in the lexicon. Additionally, having a choice of methods allows the signer to benefit from over‐specification in providing redundant information about the shape, enhancing comprehensibility and resolving ambiguity.
... Neurologically, in bimanual movements, a good majority of the research has referred to the outstanding role of motor cortex of the dominant hemisphere (Cardoso de Oliveira, 2002;Nozaki & Scott, 2009) and specifically motor cortex in the dominant hemisphere (Makia, Wonge, Sugiuraa, Ozakic, & Sadatoa, 2008). Nevertheless, in all cortex areas, the role of supplementary motor area in bimanual coordination especially in asymmetric bimanual movements has been emphasized (Goerres, Samuel, Jenkins, & Brooks, 1998;Toyokura, Muro, Komiya, & Obara, 1999). ...
Background: In most daily activities, we are required to use both of our hands. In many motor skills like playing guitar, the left and right hands must perform asymmetric movements with different timing. Objective: The aim of the study was to evaluate the effect of learning in various asymmetrical bimanual tasks and to evaluate the transfer to tasks with converse hand movements. Methods: Thirty right-handed male students (21.5 ± 1.3 years) who had no motor disorders were divided into three groups. Participants of each group were trained for four days after a pre-test. All subjects performed asymmetrical bimanual drawing of a circle with each hand. Subjects in group 1, differed in terms of load in each hand, those in group 2 differed regarding the speed of hand movement and those in group 3 differed with respect of the range of motion. The test was carried out in simultaneous bimanual movement both as practiced (learning acquisition test) and substitution of patterns between the two hands (transfer test). To analyze the data, repeated measures analysis of variance (ANOVA) was performed. Results: For the acquisition test, significant differences were found between the results of the pretest, the posttest, and the retention test across all the three groups. In terms of the transfer test, group 1 showed a significantly better performance than their performance on the acquisition (p = 0.001). No such differences were found between the performance of group 2 participants on the two tests (p = 0.945). Finally, group 3 performed significantly better on the transfer test than on the acquisition test. (p=0.047). Conclusions: The present study found similar effects of motor learning on various asymmetrical bimanual motor tasks, but different inter-group performance on learning and transfer tasks.
... Toddlers' exploration of oscillation frequency offered a possible way for them to cope with crosstalk at the neural level (e.g., de Oliveira, 2002;Oliveira & Ivry, 2008, Swinnen, 2002. That is, because of the interactions between neural command streams, interference between commands could occur, especially at high frequencies. ...
As one of the hallmarks of human activity and cultural achievement, bimanual coordination has been the focus of research efforts in multiple fields of inquiry. Since the seminal work of Cohen (1971) and Kelso and colleagues (Haken, Kelso, & Bunz, 1985; Kelso, Southard, & Goodman, 1979), bimanual action has served as a model system used to investigate the role of cortical, perceptual, cognitive, and situational underpinnings of coordinated movement sequences (e.g., Bingham, 2004; Oliveira & Ivry, 2008). This work has been guided primarily by dynamical systems theory in general, and by the formal Haken–Kelso–Bunz (HKB; 1985) model of bimanual coordination, in particular. The HKB model describes the self‐organizing relationship between a coordinated movement pattern and the underlying parameters that support that pattern, and can also be used to conceptualize and test predictions of how changes in coordination occur.
Much of the work investigating bimanual control under the HKB model has been conducted with adults who are acting over time periods of a few seconds to a few days. However, there are also changes in bimanual control that occur over far longer time spans, including those that emerge across childhood and into adolescence (e.g., Wolff, Kotwica, & Obregon, 1998). Using the formal HKB model as a starting point, we analyzed the ontogenetic emergence of a particular pattern of bimanual coordination, specifically, the anti‐phase (or inverse oscillatory motion) coordination pattern between the upper limbs in toddlers who are performing a drumming task (see Brakke, Fragaszy, Simpson, Hoy, & Cummins‐Sebree, 2007).
This study represents a first attempt to document the emergence of the anti‐phase pattern by examining both microgenetic and ontogenetic patterns of change in bimanual activity. We report the results of a longitudinal study in which seven toddlers engaged monthly in a bimanual drumming task from 15 to 27 months of age. On some trials, an adult modeled in‐phase or anti‐phase action; on other trials, no action was modeled. We documented the motion dynamics accompanying the emergence of the anti‐phase bimanual coordination pattern by assessing bout‐to‐bout and month‐to‐month changes in several movement parameters—oscillation frequency, amplitude ratio of the drumsticks, initial position of the limbs to begin bouts, and primary arm‐joint involvement. These parameters provided a good starting point to understand how toddlers explore movement space in order to achieve greater stability in performing the anti‐phase coordination pattern.
Trained research assistants used Motus software to isolate each bout of drumming and to digitize the movement of the two drumstick heads relative to the stationary drum surface. Because we were primarily interested in the vertical movement of the drumsticks that were held in the child's hands, we relied on two‐dimensional analyses and analyzed data that were tracked by a single camera. We used linear mixed effects analyses as well as qualitative analyses for each participant to help elucidate the emergence and stability of the child's use of anti‐phase coordination. This approach facilitated descriptions of individual pathways of behavior that are possible only with longitudinal designs such as the one used here.
Our analyses indicated that toddlers who were learning to produce anti‐phase motion in this context employed a variety of strategies to adjust the topography of their action. Specifically, as we hypothesized, toddlers differentially exploited oscillation frequency and movement amplitude to support change to anti‐phase action, which briefly appeared as early as 15 months of age but did not become relatively stable until approximately 20 months of age. We found evidence that many toddlers reduced oscillation frequency before transitioning from in‐phase to anti‐phase drumming. Toddlers also used different means of momentarily modulating the amplitude ratio between limbs to allow a change in coordination from in‐phase to anti‐phase. Nevertheless, these oscillation‐frequency and amplitude‐ratio strategies were interspersed by periods of nonsystematic exploration both within and between bouts of practice. We also observed that toddlers sometimes changed their initial limb positions to start a bout or altered which primary arm joints they used when drumming. When they enacted these changes, the toddlers increased performance of the anti‐phase coordination pattern in their drumming. However, we found no evidence of systematic exploration with these changes in limb position and joint employment, suggesting that the toddlers did not intentionally employ these strategies to improve their performance on the task.
Although bimanual drumming represents a highly specific behavior, our examination of the mechanisms underlying emergence of the anti‐phase coordination pattern in this context is one of the missing pieces needed to understand the development of motor coordination more broadly. Our results document that the anti‐phase coordination pattern emerges and stabilizes through modulation of the dynamics of the movement and change of the attractor landscape (i.e., the motor repertoire). Consistent with literatures in motor control, motor learning, and skill development, our results suggest that the acquisition of movements in ontogenetic development can be thought of as exploration of the emergent dynamics of perception and action. This conclusion is commensurate with a systemic approach to motor development in which functional dynamics, rather than specific structures, provide the basis for understanding developmental changes in skill. Based on our results as well as the relevant previous empirical literature, we present a conceptual model that incorporates developmental dynamics into the HKB model. This conceptual model calls for new investigations using a dynamical systems approach that allows direct control of movement parameters, and that builds on the methods and phenomena that we have described in the current work.
... We argue that the observed brain oscillatory patterns are a correlate for modulations of attentional processes during working in the dynamic office. Previous studies have demonstrated that frontal cortexes are related to executive functions, voluntary control, and action creation (Jung et al., 2000;Cardoso de Oliveira, 2002). Theta activity was shown to be related to these behaviors that demand action planning based on received sensory information Caplan et al., 2003). ...
Current research demonstrates beneficial effects of physical activity on brain functions and cognitive performance. To date, less is known on the effects of gross motor movements that do not fall into the category of sports-related aerobic or anaerobic exercise. In previous studies, we found beneficial effects of dynamic working environments, i.e., environments that encourage movements during cognitive task performance, on cognitive performance and corresponding brain activity. Aim of the present study was to examine the effects of working in a dynamic and a static office environment on attentional and vigilance performance, and on the corresponding electroencephalographic (EEG) brain oscillatory patterns. In a 2-week intervention study, participants worked either in a dynamic or a static office. In each intervention group, 12 subjects performed attentional and vigilance tasks. Spontaneous EEG was measured from 19 electrodes continuosly before, during, and immediately after each experimental condition at the first, and at the last intervention session. Results showed differences in EEG brain activity in the dynamic compared to the static office at the beginning as well as at the end of the intervention. EEG theta power increased in the vigilance task in anterior regions, alpha power in central and parietal regions in the dynamic compared to the static office. Further, increases in beta activity in the attention and vigilance task were shown in frontal and central regions in the dynamic office. Gamma power increased in the attention task in frontal and central regions. After 2 weeks, effects on brain activity increased in the attentional and vigilance task in the dynamic office. Increased theta and alpha oscillations were obtained in anterior areas with higher activity in the beta band in anterior and central areas in the dynamic compared to the static office. EEG oscillatory patterns indicate beneficial effects of dynamic office environments on attentional and vigilance performance that are mediated by increased motor activity. We discuss the obtained patterns of EEG oscillations in terms of the close interrelations between the attentional and the motor system.
... Inter-limb transfer with visuomotor adaptation tasks can be enhanced by providing visual feedback of a reversed image of the trained hand/ arm (Dionne and Henriques 2008) or by pairing intermittent passive movements of the opposite arm following the same movement as the trained arm Lei et al. 2017). Studies reporting imaging and neurophysiological findings suggest an acute bout of exercise (Rajab et al. 2014;Mang et al. 2016a;Neva et al. 2017) may influence the neural mechanisms potentially underlying inter-limb transfer (Schmidt et al. 1979;Dizio and Lackner 1995;Swinnen 2002;Cardoso de Oliveira 2002;Criscimagna-Hemminger et al. 2003;Malfait and Ostry 2004;Shadmehr 2004;Wang and Sainburg 2004). Specifically, resting-state functional magnetic resonance imaging shows that acute cycling exercise modulates co-activation of homologous sensorimotor regions (e.g., pre and postcentral gyri; Rajab et al. 2014). ...
Pairing an acute bout of lower-limb cycling exercise with skilled motor practice enhances acquisition and learning. However, it is not known whether an acute bout of exercise enhances a specific form of motor learning, namely motor adaptation, and if subsequent inter-limb transfer of this adaptation is enhanced. Seventeen young healthy participants performed a bout of cycling exercise and rest, on separate days, prior to right-arm reaching movements to visual targets under 45° rotated feedback of arm position (acquisition), followed by an immediate test of inter-limb transfer with the untrained left arm. After a 24-h delay, participants returned for a no-exercise retention test using the right and left arm with the same rotated visual feedback as acquisition. Results demonstrated that exercise enhanced right-arm adaptation during the acquisition and retention phases, and transiently enhanced aspects of inter-limb transfer, irrespective of usual levels of physical activity. Specifically, exercise enhanced movement accuracy, decreased reaction and movement time during acquisition, and increased accuracy during retention. Exercise shortened reaction time during the inter-limb transfer test immediately after right-arm acquisition but did not influence left-arm performance assessed at retention. These results indicate that an acute bout of exercise before practice enhances right-arm visuomotor adaptation (acquisition) and learning, and decreases reaction time during untrained left arm performance. The current results may have implications for the prescription of exercise protocols to enhance motor adaptation for healthy individuals and in clinical populations.
... This study provides new evidence towards the understanding of impaired bimanual function among children with USCP. It has been previously highlighted that executing bimanual tasks will activate the intact brain hemisphere, enabling neural crosstalk at different levels of the central nervous system [1,33]. Our findings show that by physically coupling the hands during a symmetric bimanual task, normal anticipation and sequencing of grasp force control, can be observed in USCP affected subjects which suggesting further ipsilateral strengthening of the intact hemisphere. ...
Background
Single object bimanual manipulation, or physically-coupled bimanual tasks, are ubiquitous in daily lives. However, the predominant focus of previous studies has been on uncoupled bimanual actions, where the two hands act independently to manipulate two disconnected objects. In this paper, we explore interlimb coordination among children with unilateral spastic cerebral palsy (USCP), by investigating upper limb motor control during a single object bimanual lifting task.
Methods
15 children with USCP and 17 typically developing (TD) children performed a simple single-object bimanual lifting task. The object was an instrumented cube that can record the contact force on each of its faces alongside estimating its trajectory during a prescribed two-handed lifting motion. The subject’s performance was measured in terms of the duration of individual phases, linearity and monotonicity of the grasp-to-load force synergy, interlimb force asymmetry, and movement smoothness.
Results
Similar to their TD counterparts, USCP subjects were able to produce a linear grasp-to-load force synergy. However, they demonstrated difficulties in producing monotonic forces and generating smooth movements. No impairment of anticipatory control was observed within the USCP subjects. However, our analysis showed that the USCP subjects shifted the weight of the cube onto their more-abled side, potentially to minimise the load on the impaired side, which suggests a developed strategy of compensating for inter-limb asymmetries, such as muscle strength.
Conclusion
Bimanual interaction with a single mutual object has the potential to facilitate anticipation and sequencing of force control in USCP children unlike previous studies which showed deficits during uncoupled bimanual actions. We suggest that this difference could be partly due to the provision of adequate cutaneous and kinaesthetic information gathered from the dynamic exchange of forces between the two hands, mediated through the physical coupling.
... Studies have demonstrated that both arms tend to produce similar forces (Heuer et al. 2002;Diedrichsen et al. 2003), directions (Swinnen et al. 2001), and frequencies (Peper et al. 1995) even when disparate movements were required for each arm. These coupling effects were not only demonstrated in behavioral movements, but also reflected in cortical control mechanisms (Cattaert et al. 1999;Cardoso de Oliveira 2002). For example, one study has found an enhancement of cortical excitability and decrement of shortinterval intracortical inhibition (SICI) of the primary motor cortex of the moving arm during active-passive bimanual mirror movement tasks (Stinear and Byblow 2004). ...
Coordinating bimanual movements is essential for everyday activities. Two common types of bimanual tasks are common goal, where two arms share a united goal, and dual goal, which involves independent goals for each arm. Here, we examine how the neural control mechanisms differ between these two types of bimanual tasks. Ten non-disabled individuals performed isometric force tasks of the elbow at 10% of their maximal voluntary force in both bimanual common and dual goals as well as unimanual conditions. Using transcranial magnetic stimulation, we concurrently examined the intracortical inhibitory modulation (short-interval intracortical inhibition, SICI) as well as the interlimb coordination strategies utilized between common- vs. dual-goal tasks. Results showed a reduction of SICI in both hemispheres during dual-goal compared to common-goal tasks (dominant hemisphere: P = 0.04, non-dominant hemisphere: P = 0.03) and unimanual tasks (dominant hemisphere: P = 0.001, non-dominant hemisphere: P = 0.001). For the common-goal task, a reduction of SICI was only seen in the dominant hemisphere compared to unimanual tasks (P = 0.03). Behaviorally, two interlimb coordination patterns were identified. For the common-goal task, both arms were organized into a cooperative "give and take" movement pattern. Control of the non-dominant arm affected stabilization of bimanual force (R2 = 0.74, P = 0.001). In contrast, for the dual-goal task, both arms were coupled together in a positive fashion and neither arm affected stabilization of bimanual force (R2 = 0.31, P = 0.1). The finding that intracortical inhibition and interlimb coordination patterns were different based on the goal conceptualization of bimanual tasks has implications for future research.
... Craske et Craske (1986) pour expliquer le couplage du post effet moteur dans leur étude avaient d'ailleurs fait appel à la théorie des « oscillateurs croisés dynamiques » (Kelso, Southard, & Goodman, 1979;Turvey, 1990). Selon cette théorie, deux oscillateurs indépendants (dans nos études les bras) se synchroniseraient lorsque ceux-ci sont en mouvement, dans une perspective bottom up de la coordination bimanuelle (Cardoso de Oliveira, 2002). Ces effets expliqueraient bien nos résultats sur l'activité motrice involontaire avec une coordination des deux bras sans qu'aucune commande motrice ne soit envoyée au bras face au miroir et seulement sur la base d'informations sensorielles proprioceptives, sans retour visuel (Etude 4). ...
Le schéma corporel est une représentation interne et dynamique du corps, de la morphologie, et des positions relatives des segments corporels. Celui-ci serait le support à partir duquel une motricité adaptée va pouvoir se mettre en place. L’objectif principal de ce travail doctoral était d’évaluer plus précisément cette intrication entre schéma corporel et comportements moteurs. Nous avons ainsi évalué à la fois l'effet de différentes distorsions du schéma corporel sur le comportement moteur, et inversement l'effet des comportements moteurs sur la modulation éventuelle du schéma corporel.Tout d’abord, nous avons testé si la distorsion morphologique du schéma corporel rapportée récemment dans l’anorexie mentale avait un retentissement sur la locomotion des patientes, dans une tâche de passabilité d’ouvertures (Etude 1). Les patientes ont effectivement tourné leurs épaules pour des largeurs d’ouvertures qui, compte tenu de leur nouvelle morphologie, ne nécessitaient pas une telle contorsion. Des comportements moteurs identiques ont été observés chez une patiente ayant perdu massivement et rapidement du poids, mais sans souffrir d’anorexie mentale (Etude 2). Ces résultats dans leur ensemble soulignent la rigidité du schéma corporel face à des changements corporels majeurs, ainsi que son incidence forte sur le comportement moteur dans l’anorexie mentale.Dans un deuxième temps, nous avons induit chez le sujet sain, grâce au paradigme miroir, souvent utilisé en réadaptation motrice, une distorsion entre schéma corporel et segments corporels, afin d’en évaluer les conséquences sur le comportement moteur volontaire (coordination bimanuelle, Etude 3) et involontaire (post-effet moteur, Etude 4). Les résultats de nos études font apparaître que la modulation des comportements moteurs dans le paradigme miroir serait plus liée aux afférences proprioceptives du bras face au miroir ou encore à une meilleure répartition des processus attentionnels, plutôt qu’à la distorsion du schéma corporel via le miroir.Enfin, nous avons testé si les comportements moteurs, ou tout du moins l’intention motrice à l’origine, pouvaient en retour moduler le schéma corporel et le sens du mouvement (Etude 5). Les illusions de mouvement induites dans le paradigme miroir ont bien été modulées selon que l’intention motrice du bras soumis à l’illusion soit congruente ou non avec le sens du mouvement illusoire généré.Compte tenu de l’implication de l’intention motrice dans la mise à jour du schéma corporel, nous suggérons que la prise en charge des troubles du schéma corporel (e.g. dans l’anorexie mentale), souvent basée sur une réadaptation visuelle de la représentation du corps, devrait être complétée par une remédiation sensori-motrice.Mots clefs : schéma corporel, comportement moteur, anorexie mentale, paradigme miroir, kinesthésie
... Previous investigations of the neural control of bimanual tasks have provided somewhat different 63 explanations for how the central nervous system (CNS) controls the multiple degrees-of-freedom (DOFs) 64 associated with these tasks (de Oliveira, 2002). The framework of generalized motor programs (Schmidt, 65 1975) suggests that a 'general', unified motor program controls the movements of both arms, and can be 66 'fine-tuned' to produce asymmetric movements in cases where independent limb movements are required 67 (Kelso et al., 1979). ...
New & noteworthy:
This study investigated the effects of somatosensory feedback during bimanual tasks on the neural coupling between arm muscles, which remains largely unexplored. Somatosensory feedback using a balancing apparatus, compared with visual feedback, significantly increased neural coupling between homologous muscles (indicated by intermuscular coherence values) and improved temporal correlation of bilateral force production. Notably, feedback type modulated coherence in the α- and γ-bands (more subcortical pathways), whereas task type mainly affected β-band coherence (corticospinal pathway).
... This arrangement is reinforced even only a few hours after stroke [35], which is partially due to compensation by the unaffected arm [36,37]. As a result, the unaffected arm gains stronger independence than it would in physiological conditions and the paretic one is excluded when complex motor operations require bilateral coordination [38]. Only 30% to 66% of patients reach a satisfactory functional recovery of the upper limb [39][40][41]. ...
Background:
In recent years, as part of the rehabilitation of post stroke patients, the use of robotic technologies to improve recovery of upper limb has become more widespread. The Automatic Recovery Arm Motility Integrated System (ARAMIS) is a concept robot and prototype designed to promote the functional interaction of the arms in the neurorehabilitation of the paretic upper limb. Two computer-controlled, symmetric and interacting exoskeletons compensate for the inadequate strength and accuracy of the paretic arm and the effect of gravity during rehabilitation. Rehabilitation is possible in 3 different modalities; asynchronous, synchronous and active-assisted.
Objectives:
To compare the effectiveness of robotic rehabilitation by an exoskeleton prototype system with traditional rehabilitation in motor and functional recovery of the upper limb after stroke.
Methods:
Case-control study, 52 patients enrolled in the study, 28 cases (women: 8, age: 65 ± 10 yrs) treated with ARAMIS and 24 controls (women: 11, age: 69 ± 7 yrs) with conventional rehabilitation. Motor impairment assessed before and after treatment with Fugl-Meyer scale and Motricity Index, level of disability assessed with the Functional Independence Measure. A questionnaire was also administered to assess the patient's tolerance to robotic therapy.
Results:
After 28 ± 4 sessions over a 54 ± 3.6-day period, the patients treated by ARAMIS had an improvement on the Fugl-Meyer scale (global score from 43 ± 18 to 73 ± 29; p < 0.00001), Motricity Index scale (p < 0.004) and Functional Independence Measure (p < 0.001). A lesser degree of improvement was achieved using conventional rehabilitation, the Fugl-Meyer global score of the control group improved from 41 ± 13 to 58 ± 16 (p < 0.006) and the motor function item from 9.4 ± 4.1 to 14.9 ± 5.8 (p < 0.023).
Conclusions:
Motor improvement was greater at the wrist and hand than at shoulder and elbow level in patients treated by ARAMIS and controls, but it was significantly greater in ARAMIS-treated patients than in controls. The results indicate a greater efficacy of ARAMIS compared to conventional rehabilitation.
... Essentially, these phonological constraints require that (a) the non-dominant hand copy the handshape and movement of the dominant hand if both hands move and (b) the non-dominant hand can serve as a passive (non-moving) base of articulation but is restricted to a small set of unmarked, simple handshapes. Although much is known about bimanual articulation processes for non-linguistic hand and finger movements (see Cardoso de Oliveira (2002) and Swinnen and Wenderoth (2004) for reviews), almost nothing is known about the nature of bimanual movements when they are internally generated and bound to a linguistic representation. Studies of nonlinguistic movement have indicated that activation in the SMA (and the cingulate motor cortex) is more pronounced during bimanual than unimanual articulation, suggesting this region is involved in coordinating actions produced with two effectors (i.e., arms, hands, or fingers; e.g., Jäncke et al., 2000;Toyokura, Muro, Komiya, & Obara, 2002). ...
Signing differs from typical non-linguistic hand actions because movements are not visually guided, finger movements are complex (particularly for fingerspelling), and signs are not produced as holistic gestures. We used positron emission tomography to investigate the neural circuits involved in the production of American Sign Language (ASL). Different types of signs (one-handed (articulated in neutral space), two-handed (neutral space), and one-handed body-anchored signs) were elicited by asking deaf native signers to produce sign translations of English words. Participants also fingerspelled (one-handed) printed English words. For the baseline task, participants indicated whether a word contained a descending letter. Fingerspelling engaged ipsilateral motor cortex and cerebellar cortex in contrast to both one-handed signs and the descender baseline task, which may reflect greater timing demands and complexity of handshape sequences required for fingerspelling. Greater activation in the visual word form area was also observed for fingerspelled words compared to one-handed signs. Body-anchored signs engaged bilateral superior parietal cortex to a greater extent than the descender baseline task and neutral space signs, reflecting the motor control and proprioceptive monitoring required to direct the hand toward a specific location on the body. Less activation in parts of the motor circuit was observed for two-handed signs compared to one-handed signs, possibly because, for half of the signs, handshape and movement goals were spread across the two limbs. Finally, the conjunction analysis comparing each sign type with the descender baseline task revealed common activation in the supramarginal gyrus bilaterally, which we interpret as reflecting phonological retrieval and encoding processes.
... People even switch into symmetry when executing parallel movements, but usually not vice versa (Mechsner, Kerzel, Knoblich, & Prinz, 2001). This symmetry tendency is due to a Bcoalition of constraints^ (Swinnen & Wenderoth, 2002), present at the motor level (e.g., due to neuronal crosstalk of motor commands between the hemispheres; Cardoso de Oliveira, 2002;Swinnen et al., 1997) and at the perceptualcognitive level (Mechsner et al., 2001). ...
Motor imagery and motor execution share similar processes. However, only some factors that affect motor execution affect motor imagery in the same way. We investigated whether bimanual coordination constraints (parallel movements are performed slower than symmetric movements) are observed in motor imagery and whether the way of implementing the mental chronometry paradigm, which is used to investigate motor imagery, influences the results. Participants imagined and executed repetitive symmetric and parallel bimanual movements in three different tasks. Participants performed a certain number of movement repetitions (number task), repeated movements for a fixed duration (duration task), and performed movements in synchrony with pacing sounds (synchronization task). In both, imagination and execution, inter-response intervals were longer with parallel movements than with symmetric movements (number task and duration task), and the percentage of correct movements was lower with parallel than with symmetric movements (synchronization task). Performance of imagined and executed movements was correlated in all tasks. However, imagination took longer or was rated as less accurate than execution, and in the synchronization task the coordination constraint affected accuracy more in execution than in imagination. Thus, motor imagery and overt execution involve shared and unique processes. The synchronization task offers a promising alternative to investigate motor imagery, because the speed-accuracy trade-off is taken into account, different tempi can be used, and psychometric functions can be calculated.
Electronic supplementary material
The online version of this article (doi:10.3758/s13414-016-1112-9) contains supplementary material, which is available to authorized users.
... As these spatial costs persist even after extended preparation time and independent of cue, they likely constitute static, execution-related sources of inference (Heuer 1993; Heuer et al. 2001). This experiment demonstrates again that bimanual interference results from interactions of codes on multiple levels (Cardoso de Oliveira 2002) and that the manner in which actions are conceptualized may have a dramatic influence on whether or not spatial interactions are manifest in the preparation of bimanual movements. With direct cues, the actions are specified in terms of target locations. ...
We argue that bimanual coordination and interference depends critically on how these actions are represented on a cognitive level. We first review the literature on spatial interactions, focusing on the difference between movements directed at visual targets and movements cued symbolically. Interactions manifest during response planning are limited to the latter condition. These results suggest that interactions in the formation of the trajectories of the two hands are associated with processes involved in response selection, rather than interactions in the motor system. Neuropsychological studies involving callosotomy patients argue that these interactions arise from transcallosal interactions between cortically-based spatial codes. The second half of the chapter examines temporal constraints observed in bimanual movements. We propose that most bimanual movements are marked by a common event structure, an explicit representation that ensures temporal coordination of the movements. The translation of an abstract event structure into a movement with a particular timing pattern is associated with cerebellar function, although the resulting temporal coupling during bimanual movements may be due to the operation of other subcortical mechanisms. For rhythmic movements that do not entail an event structure, timing may be an emergent property. Under such conditions, both spatial and temporal coupling can be absent. The emphasis on abstract levels of constraint makes clear that limitations in bimanual coordination overlap to a considerable degree with those observed in other domains of cognition.
... In order to implement human-like synchronous movements in a bimanual anthropomorphic robot, it is necessary to understand the basis of bimanual coordination in humans and the functional models (based on neuro-physiological evidences) that have been proposed. Recent data acquired address three conceptual areas [1]: the generalized motor program (GMP), intermanual crosstalk, dynamic system models. Although controversial studies exist on each one of these approaches, the proposed motion planner takes inspiration by those models that represent synergies of muscles easily controlled jointly as a singular functional unit and explain the strong tendency for synchronous timing of bimanual movements (e.g. ...
In previous work we have presented a model capable of generating human-like movements for a dual arm-hand robot involved in human-robot cooperative tasks. However, the focus was on the generation of reach-to-grasp and reach-to- regrasp bimanual movements and no synchrony in timing was taken into account. In this paper we extend the previous model in order to accomplish bimanual manipulation tasks by synchronously moving both arms and hands of an anthropomorphic robotic system. Specifically, the new extended model has been designed for two different tasks with different degrees of difficulty. Numerical results were obtained by the implementation of the IPOPT solver embedded in our MATLAB simulator.
... Although some of the previous studies have investigated the human arm motion during bi-manual tasks, inter-arm coordination has not been adequately understood. From the neurophysiology point of view, there are many studies that provide evidence that bi-manual tasks are governed by coordination patterns encoded in neural level [9,12,37,39,43]. However, a kinematic coordination model for bi-manual tasks is still to be defined. ...
As robots begin to permeate the everyday human workspace to collaborate in innumerable and varied tasks, the robotic structure must adhere and replicate human-like gestures for effective interaction. Whether rehabilitation or augmentation, upper arm human-robot interaction is some of the most prevalent and investigated forms of collaboration. However, currently robotic control schemes fail to capture the true intricacies of anthropomorphic motion and intent during simple bi-manual manipulation tasks. This paper focuses on the introduction of bio-inspired control schemes for robot manipulators that coordinate with humans during dual arm object manipulation. Using experimental data captured from human subjects performing a variety of every-day bi-manual life tasks, we propose a bio-inspired controller for a robot arm, that is able to learn human inter- and intra-arm coordination during those tasks. Using dimensionality reduction techniques to make comprehensible the linear correlations of both arms in joint space we fit and utilize potential fields that attract the robot to human-like configurations. This method is then tested using real experimental data across multiple bi-manual tasks with a comparison made between the bio-inspired and traditional inverse kinematic controllers. Using a robotic kinematic chain identical to the human arm, models are evaluated for anthropomorphic configurations.
... According to the research of Oliveira, (26) information about the movement that is acquired by the sensory system for one side of the limb is transferred to the other side, thus helping to effect its movement. A common assumption for this information exchange is that facilitation and interference effects are achieved because of the interhemispheric crosstalk through the corpus callosum in the brain. ...
Recently, bilateral movement training based on robot-assisted rehabilitation systems has been attracting a lot of attention as a post-stroke motor rehabilitation protocol. Since humans generate coordinated motions based on their motor and sensory system, investigation of the innate properties of human motor and sensory systems may provide insight into planning of effective bilateral movement training in motion. In this study, therefore, we investigate the effects of proprioception and handedness on the movements of the contra-lateral upper limb, under both active and passive robot guidance conditions of the robot manipulators. Active and passive guidance-reproduction based bimanual tasks were used in this study; in these the subject is asked to hold both right and left knobs installed at the end-effectors of two robot manipulators. The results indicate that better reproducing performance was obtained when the proprioceptive input was acquired from the active guidance condition.
... Because of this functional topography, it was expected that atrophy of specific subregions, connected with cortical regions relevant for sensorimotor performance, would mediate age-related bimanual performance declines. Indeed, these thalamic subregions corresponded with the thalamic connectivity profile to the premotor, primary motor and somatosensory areas (Johansen-Berg et al., 2005), which are known to play a crucial role in bimanual coordination (Cardoso de Oliveira, 2002; Swinnen & Wenderoth, 2004). In the current study, we tested the very specific hypothesis that age-related atrophy of subregions of the bilateral thalamus , putamen, caudate and pallidum, which are connected with cortical regions involved in motor control, accounts for age-related bimanual performance declines. ...
... This idea is supported by an abundance of literature that has demonstrated an assimilation effect whereby both limbs tend to produce similar amplitudes (e.g., Heuer, Kleinsorge, Spijkers, & Steglich, 2001;Sherwood, 1994;Spijkers & Heuer, 1995), directions (e.g., Franz, Eliassen, Ivry, & Gazzaniga, 1996;Swinnen, Dounskaia, & Duysens, 2002;Swinnen, Dounskaia, Levin, & Duysens, 2001), frequencies (e.g., Peper, Beek, & van Wieringen, 1995b, c;Treffner & Turvey, 1993), or forces (e.g., Diedrichsen, Hazeltine, Nurss, & Ivry, 2003;Heuer, Spijkers, Steglich, & Kleinsorge, 2002;Steglich, Heuer, Spijkers, & Kleinsorge, 1999) despite task goals requiring disparate activation patterns for the two limbs. Because neural crosstalk conveys the same information to both limbs via cortical and subcortical pathways, it is believed that symmetrical actions are stabilized when complementary contralateral and ipsilateral signals are integrated while asymmetric actions can suffer from ongoing interference due to conflicting information or partial intermingling of signals controlling the two arms (Cardoso de Oliveira, 2002;Kagerer, Summers, & Semjen, 2003;Maki, Wong, Sugiura, Ozaki, & Sadato, 2008;Marteniuk, MacKenzie, & Baba, 1984). However, a clear understanding of how and when crosstalk facilitates or inhibits coordinated actions between the limbs has yet to be proposed. ...
Three experiments were designed to determine the level of cooperation or interference observed from the forces generated in one limb on the forces exhibited by the contralateral limb when one or both limbs were producing a constant force (Experiment 1), one limb was producing a dynamic force while the other limb was producing a constant force (Experiment 2), and both limbs were producing dynamic force patterns (Experiment 3). The results for both Experiments 1 and 2 showed relatively strong positive time series cross correlations between the left and right limb forces indicating increases or decreases in the forces generated by one limb resulted in corresponding changes in the forces produced by the homologous muscles of the contralateral limb. Experiment 3 required participants to coordinate 1:1 and 1:2 rhythmical bimanual force production tasks when provided Lissajous feedback. The results indicated very effective performance of both bimanual coordination patterns. However, identifiable influences of right limb forces on the left limb force time series were observed in the 1:2 coordination pattern but not in the 1:1 pattern. The results of all three experiments support the notion that neural crosstalk is partially responsible for the stabilities and instabilities associated with bimanual coordination.
... For discrete, goal-directed movements, there is not necessarily a bias for mirror movements; this is likely due to control of these movements depending more on posterior-parietal networks (Desmurget et al. 1999), which code visual targets in gaze-centered (allocentric) coordinates (Buneo and Andersen 2006), thus facilitating isodirectional bimanual coordination over anisodirectional (mirror) movements in the presence of visual targets. The mirror movements observed in the small subsample of participants could be mediated by several factors, one of which is neural crosstalk at an executional level (Cardoso de Oliveira 2002). In this scenario, a fraction of the force commands originating in the dominant motor cortex would descend ipsilaterally as mirror image (Cattaert et al. 1999), resulting in lower activation of the non-dominant motor cortex. ...
Studies on bimanual control inevitably deal with questions about interactions between the two effectors, mostly under conditions of sensory feedback of the same modality-usually vision-for both hands. This study used a novel paradigm in which one hand performed target-directed movements under visual control, while the other hand operated under predominantly kinesthetic control, without visual feedback. By introducing an abrupt visual feedback perturbation in the 'visible' hand, resulting in an update of its visuo-motor map, the robustness of the kinesthetic-motor map of the 'invisible' hand against interference from the visually controlled hand could be tested. Results show that the visuo-motor adaptation resulted in asymmetric directional interference: when the 'visible' right hand adapted to the perturbation, it interfered substantially more with the 'invisible' left hand (group 1) than when the left hand was under visual control and the right hand under kinesthetic control (group 2). The results support recent theories of functional lateralization postulating dominance of the right hand for trajectory control and demonstrate that on the level of arm kinematics, this interference crosses modality boundaries. Interestingly, while in most participants interference manifested itself in isodirectional deviations of the kinesthetically guided hand, the deviations in a small subsample of participants mirrored those of the visually guided hand. The results are discussed in the context of potential neural crosstalk.
Many movements in daily life are embedded in motion sequences that involve more than one limb, demanding the motor system to monitor and control different body parts in quick succession. During such movements, systematic changes in the environment or the body might require motor adaptation of specific segments. However, previous motor adaptation research has focused primarily on motion sequences produced by a single limb, or on simultaneous movements of several limbs. For example, adaptation to opposing force fields is possible in unimanual reaching tasks when the direction of a prior or subsequent movement is predictive of force field direction. It is unclear, however, whether multi-limb sequences can support motor adaptation processes in a similar way. In the present study (38 females, 38 males), we investigated whether reaches can be adapted to different force fields in a bimanual motor sequence when the information about the perturbation is associated with the prior movement direction of the other arm. In addition, we examined whether prior perceptual (visual or proprioceptive) feedback of the opposite arm contributes to force field-specific motor adaptation. Our key finding is that only active participation in the bimanual sequential task supports pronounced adaptation. This result suggests that active segments in bimanual motion sequences are linked across limbs. If there is a consistent association between movement kinematics of the linked and goal movement, the learning process of the goal movement can be facilitated. More generally, if motion sequences are repeated often, prior segments can evoke specific adjustments of subsequent movements.
Significance statement
Movements in a limb’s motion sequence can be adjusted based on linked movements. A prerequisite is that kinematics of the linked movements correctly predict which adjustments are needed. We show that use of kinematic information to improve performance is even possible when a prior linked movement is performed with a different limb. For example, a skilled juggler might have learned how to correctly adjust his catching movement of the left hand when the right hand performed a throwing action in a specific way. Linkage is possibly a key mechanism of the human motor system for learning complex bimanual skills. Our study emphasizes that learning of specific movements should not be studied in isolation but within their motor sequence context.
Previous research has indicated that neural crosstalk is asymmetric, with the dominant effector exerting a stronger influence on the non-dominant effector than vice versa. Recently, it has been hypothesized that this influence is more substantial for proximal than distal effectors. The current investigation was designed to determine the effects of distal ((First Dorsal Interosseous (FDI)) and proximal (triceps brachii (TBI)) muscle activation on neural crosstalk. Twelve right-limb dominant participants (mean age = 21.9) were required to rhythmically coordinate a 1:2 pattern of isometric force guided by Lissajous displays. Participants performed 10, 30 s trials with both distal and proximal effectors. Coherence between the two effector groups were calculated using EMG-EMG wavelet coherence. The results indicated that participants could effectively coordinate the goal coordination pattern regardless of the effectors used. However, spatiotemporal performance was more accurate when performing the task with distal than proximal effectors. Force distortion, quantified by harmonicity, indicated that more perturbations occurred in the non-dominant effector than in the dominant effector. The results also indicated significantly lower harmonicity for the non-dominant proximal effector compared to the distal effectors. The current results support the notion that neural crosstalk is asymmetric in nature and is greater for proximal than distal effectors. Additionally, the EMG-EMG coherence results indicated significant neural cross-talk was occurring in the Alpha bands (5-13 Hz), with higher values observed in the proximal condition. Significant coherence in the Alpha bands suggest that the influence of neural crosstalk is occurring at a subcortical level.
Recent neuroimaging studies allowed us to explore abnormal brain structures and interhemispheric connectivity in children with cerebral palsy (CP). Behavioral researchers have long reported that children with CP exhibit suboptimal performance in different cognitive domains (e.g., receptive and expressive language skills, reading, mental imagery, spatial processing, subitizing, math, and executive functions). However, there has been very limited cross-domain research involving these two areas of scientific inquiry. To stimulate such research, this perspective paper proposes some possible neurological mechanisms involved in the cognitive delays and impairments in children with CP. Additionally, the paper examines the ways motor and sensorimotor experience during the development of these neural substrates could enable more optimal development for children with CP. Understanding these developmental mechanisms could guide more effective interventions to promote the development of both sensorimotor and cognitive skills in children with CP.
Objective: Bilateral coordination skills are one of the key factors in performing simple to skillful sports task, so far the differences between ball and non-ball fields have not been determined. Therefore, this study aimed to investigate the differences in asymmetric bilateral coordination between male and female athletes in ballplayers and non-ballplayers. Methods: The samples of this study were randomly selected from the young girls and boys (Mean±SD of age 26.00±4.50) in ball fields (14) and non-ball fields (16) of the Faculty of Physical Education of the University of Tehran. All subjects had complete visual acuity and the consent form of the research. The instrument of Vienna was used to measure peripheral visual. Results: The statistical results of MANOVA test showed that there is significant difference in asymmetrical bilateral coordination between ballplayers and non-ballplayers and girls and boys (P≥0.05). Conclusion: The results of this study showed that asymmetric bilateral coordination performing in ball players had better than non-ball players and girls than boys. According the importance of bimanual coordination skills in the implementation of championship sports, as well as considering gender differences and the positive impact of ball exercises on ball coordination, sports coaches can provide training, especially at a younger age, to facilitate learning of this fundamental skill.
In an experiment conducted by Kennedy et al. (Exp Brain Res 233:181–195, 2016), dominant right-handed individuals were required to produce a rhythm of isometric forces in a 2:1 or 1:2 bimanual coordination pattern. In the 2:1 pattern, the left limb performed the faster rhythm, while in the 1:2 pattern, the right limb produced the faster pattern. In the 1:2 pattern, interference occurred in the limb which had to produce the slower rhythm of forces. However, in the 2:1 condition, interference occurred in both limbs. The conclusion was that interference was not only influenced by movement frequency, but also influenced by limb dominance. The present experiment was designed to replicate these findings in dynamic bimanual 1:2 and 2:1 tasks where performers had to move one wrist faster than the other, and to determine the influence of limb dominance. Dominant left-handed ( N = 10; LQ = − 89.81) and dominant right-handed ( N = 14; LQ = 91.25) participants were required to perform a 2:1 and a 1:2 coordination pattern using Lissajous feedback. The harmonicity value was calculated to quantify the interference in the trial-time series. The analysis demonstrated that regardless of limb dominance, harmonicity was always lower in the slower moving limb than in the faster moving limb. The present results indicated that for dominant left- and dominant right-handers the faster moving limb influenced the slower moving limb. This is in accordance with the assumption that movement frequency has a higher impact on limb control in bimanual 2:1 and 1:2 coordination tasks than handedness.
In a bimanual task, proprioception provides information about position and movement of upper arms. Developmental studies showed improvement of proprioceptive accuracy and timing adjustments of muscular events from childhood to adulthood in bimanual tasks. However, the cortical maturational changes related to bimanual coordination is not fully understood. The aim of this study was to investigate cortical correlates underlying motor planning and upper limb stabilization performance at left (C3) and right (C4) sensorimotor cortices using event-related potential (ERP) analyses. We recruited 46 participants divided into four groups (12 children: 8-10 years, 13 early adolescents: 11-13 years, 11 late adolescents: 14-16 years and 10 young adults: 20-35 years). Participants performed a bimanual load-lifting task, where the left postural arm supported the load and the right motor arm lifted the load. Maximal amplitude of elbow rotation (MA%) of the postural arm, reaction time (RT) and EMG activity of biceps brachii bilaterally were computed. Laplacian-transformed ERPs of the electroencephalographic (EEG) signal response-locked to motor arm biceps EMG activity onset were analyzed over C3 and C4. We found a developmental effect for behavioral and EEG data denoted by significant decrease of MA% and RT with age, earlier inhibition of the biceps brachii of the postural arm in adults and earlier EEG activation/inhibition onset at C3/C4. Amplitude of the negative wave at C4 was higher in children and early adolescents compared to the other groups. In conclusion, we found a maturational process in cortical correlates related to motor planning and upper limb stabilization performance with interhemispheric lateralization appearing during adolescence. Findings may serve documenting bimanual performance in children with neurodevelopmental disorders.
Background
Morphology builds Wilson's disease's clincal basis.
Objectives
To detect and quantify regional morphometric abnormalities, in terms of both volume and shape, in patients with Wilson's disease.
Methods
Twenty‐seven Wilson's disease patients and 24 healthy controls were enrolled. Specific brain structures, including the bilateral caudate, putamen, globus pallidus, thalamus, amygdala, hippocampus, red nucleus, and substantia nigra (SN), were automatically extracted from each participant's T1‐weighted image. Volume abnormalities and correlations with the modified Young scale were investigated. Furthermore, vertex‐based shape analysis was performed to explore region‐specific morphometric abnormalities.
Results
Significant global volume atrophy and local shape abnormalities were detected and quantified in the bilateral caudate, putamen, globus pallidus, thalamus, amygdala, red nucleus, and SN. Morphometric abnormalities of the caudate, putamen, and thalamus were strong, whereas those of the globus pallidus, amygdala, red nucleus, and SN were weaker. No hippocampal abnormalities were observed. The modified Young scale was found to correlate significantly with the volumes of the bilateral putamen and the right globus pallidus. Shape analysis revealed subregion‐specific atrophy of the bilateral caudate and putamen. They were concentrated in the subregions that project to the limbic and executive cortices. Significant region‐specific atrophy was also detected in the bilateral thalamic subregions that project to the primary motor, sensory, and premotor cortices.
Conclusions
We found significant morphometric abnormalities of specific structures of interest in patients with Wilson's disease, both globally and locally. These morphometric abnormalities may serve as useful imaging biomarkers for Wilson's disease. © 2019 International Parkinson and Movement Disorder Society
Previous theoretical and empirical work indicates that intentional changes in a bimanual coordination pattern depends on the stability of the bimanual coordination pattern (Kelso, Schotz, & Schöner, 1988; Scholz & Kelso, 1990). The present experiments retest this notion when online Lissajous displays are provided. Switching to and from in-phase and antiphase and to and from 90° and 270° were tested in Experiment 1. Participants were able to very effectively produce the 180°, 90°, and 270° coordination patterns although performance of the in-phase coordination task was even more stable. The data indicated that switching to in-phase from antiphase was more rapid than vice versa and that switching times between 90° to 270° were similar. Experiment 2 investigated switching between 1:2 and 2:1 bimanual coordination patterns. The results indicated that switching time was similar between the 2:1 and 1:2 coordination tasks and that increases in stability over practice resulted in additional decreases in switching times. This provides additional evidence that the attractor landscape is fundamentally different dependent on the type of information provided the performer. What remains to be done is to reconcile these results with the various theories/perspectives currently used to describe and explain bimanual coordination.
In 10 tested dextral subjects, EEG activity was recorded during the performance of unimanual and bimanual cyclic movements of the hands and fingers. The movements corresponded to clenching the fingers into a fist and the subsequent unclenching of the fingers. The test consisted of four successive stages, the resting state, movement of the left hand, that of the right hand, and movement of both hands. The dependences between the spectral power and coherence of the respective EEG samples on the type of the test performed, on the type of the movement (uni- or bimanual), and on the laterality of the latter in the case of the unimanual movement were examined. The results obtained allow us to propose the following conclusions: (i) α and β EEG rhythms are characterized by different functional importance with respect to manual motor activity; (ii) neural control of bimanual movements cannot be considered “a sum of the controls” of unimanual movements, and (iii) control of bimanual movements may be largely based on the control of the movement by a subdominant upper limb.
An experiment was designed to determine the impact of the force requirements on the production of bimanual 1:2 coordination patterns requiring the same (symmetric) or different (asymmetric) forces when Lissajous displays and goal templates are provided. The Lissajous displays have been shown to minimize the influence of attentional and perceptual constraints allowing constraints related to neural crosstalk to be more clearly observed. Participants (N=20) were randomly assigned to a force condition in which the left or right limb was required to produce more force than the contralateral limb. In each condition participants were required to rhythmically coordinate the pattern of isometric forces in a 1:2 coordination pattern. Participant performed 13 practice trials and 1 test trial per force level. The results indicated that participants were able to effectively coordinate the 1:2 multi-frequency goal patterns under both symmetric and asymmetric force requirements. However, consistent distortions in the force and force velocity time series were observed for one limb that appeared to be associated with the production of force in the contralateral limb. Distortions in the force produced by the left limb occurred regardless of the force requirements of the task (symmetric, asymmetric) or whether the left or right limb had to produce more force than the contralateral limb. However, distinct distortions in the right limb occurred only when the left limb was required to produce 5 times more force than the right limb. These results are consistent with the notion that neural crosstalk can influence both limbs, but may manifest differently for each limb depending on the force requirements of the task.
According to the characteristics of EMGs subjected to full-wave rectification and low-pass filtering, we examined coordination of central motor commands coming to muscles of the shoulder belt and shoulders in the course of realization of cyclic bimanual movements within a horizontal plane (close to those in sculling). The performance of different motor tasks was tested: (i) movements at a comfortable stroke rate (CSR); (ii) movements at a maximum rate (MR), and (iii) movements with the feedback (FB) information, where the subject could trace the movement rate and angles of rotation of one lever of the experimental set. Two levels of external loading could be applied to the levers of the set (“oars”) in the direction counteracting efforts developed by the subject within the pulling phase. It was found that, in realization of the CSR test, the movement rate was greater at a higher loading than that in the case of a smaller mechanical resistance. The mean level of EMGs of the examined muscles under conditions of a higher loading in realization of the CSR test was greater than that in the FB test. The level of activation of the muscles in the course of the MR test demonstrated no dependence of the level of external loading. The level of correlations between EMG activities of similar muscles of the left and right upper limbs demonstrated a trend toward lowering under conditions of the presence of visual FB. It is supposed that the cognitive influence upon realization of the motor tasks is intensified under the above conditions, and the type of the performed movements becomes closer to the discrete mode.
The experiment was conducted to determine the influence of mirror movements in bimanual coordination during life span. Children, young adults, and older adults were instructed to perform a continuous 1:2 bimanual coordination task by performing flexion-extension wrist movements over 30s where symmetrical and non-symmetrical coordination patterns alternate throughout the trial. The vision of the wrists was covered and Lissajous-feedback was provided online. All age groups had to perform 10 trials under three different load conditions (0kg, .5kg, 1.0kg: order counterbalanced). Load was manipulated to determine if increased load increases the likelihood of mirror movements. The data indicated that the performance of the young adults was superior compared to the children and older adults. Children and older adults showed a stronger tendency to develop mirror movements and had particular difficulty in performing the non-symmetrical mode. This type of influence may be attributed to neural crosstalk.
During the past years, several studies have addressed the neural basis of interlimb coordination by means of imaging techniques, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). The general picture emerging from these studies is that a network consisting of the cerebellum, SMA and dorsal premotor cortex becomes particularly activated during demanding interlimb coordination tasks. Additionally, other regions such as Broca’s area, ventral premotor cortex as well as secondary sensory areas appear to become involved when rhythmic interlimb tasks require increased monitoring of the individual limb motions performed in accordance to an imposed rhythm.
Executed bimanual movements are prepared slower when moving to symbolically different than when moving to symbolically same targets and when targets are mapped to target locations in a left/right fashion than when they are mapped in an inner/outer fashion [Weigelt et al. (Psychol Res 71:238-447, 2007)]. We investigated whether these cognitive bimanual coordination constraints are observable in motor imagery. Participants performed fast bimanual reaching movements from start to target buttons. Symbolic target similarity and mapping were manipulated. Participants performed four action conditions: one execution and three imagination conditions. In the latter they indicated starting, ending, or starting and ending of the movement. We measured movement preparation (RT), movement execution (MT) and the combined duration of movement preparation and execution (RTMT). In all action conditions RTs and MTs were longer in movements towards different targets than in movements towards same targets. Further, RTMTs were longer when targets were mapped to target locations in a left/right fashion than when they were mapped in an inner/outer fashion, again in all action conditions. RTMTs in imagination and execution were similar, apart from the imagination condition in which participants indicated the start and the end of the movement. Here MTs, but not RTs, were longer than in the execution condition. In conclusion, cognitive coordination constraints are present in the motor imagery of fast (<1600 ms) bimanual movements. Further, alternations between inhibition and execution may prolong the duration of motor imagery.
-Dominant (right) and nondominant (left) hand differences in motor performance variables were investigated during targeted rapid aiming unimanual and bimanual (to two separate targets) speed-accuracy tasks. The performance of the dominant and nondominant hands were compared during rapid targeted unimanual and bimanual reaching tasks (50 repetitions) in adult, neurologically intact, right-handed men (n = 20). As task difficulty increased from unimanual to bimanual tasks, reaction time increased and velocity (average and maximal) of performance decreased significantly. The effect of hand was significant only on average movement velocity and on intraindividual variability of accuracy (in both cases performance in the left hand was worse). Variability of movement path (accuracy) was less in the right hand during both unimanual and bimanual tasks.
To obtain a better understanding of the cortical representation of bimanual coordination, we measured regional cerebral blood flow (rCBF) with ¹⁵ O-labeled water and positron emission tomography (PET). To detect areas with changes of rCBF during bimanual finger movements of different characteristics, we studied 12 right-handed normal volunteers. A complete session consisted of three rest scans and six scans with acoustically paced (1 Hz) bimanual, mirror, or parallel sequential finger movements. Activation of the right dorsal premotor area (PMd) extending to the posterior supplementary motor area (SMA) was significantly stronger during the parallel movements than during the mirror sequential movements ( p < 0.05, at cluster level with correction for multiple comparisons). To determine whether these cortical areas truly represented bimanual coordination, a different group of nine normal volunteers was studied with a different task. Subjects performed acoustically paced (2 Hz) abduction–adduction movements of the index finger, making right only, left only, and bimanual mirror and parallel movements. Activation of the posterior SMA and right PMd was significantly greater during the parallel movements than during the bimanual mirror movements or the unimanual movements of either hand ( p < 0.01, with anatomical constraint). Thus, the posterior SMA and right PMd appear to be related to the bimanual coordination of finger movements.
In recent years VOGEL and BOGEN, both neurosurgeons at the White Memorial Hospital in Los Angeles, have used surgical division of the neocommissures to treat a number of patients for intractable epilepsy. This measure was always a last effort to alleviate advancing, life-threatening convulsions and for most patients so far has brought remarkable improvements (BOGEN et al., 1965; BOGEN and VOGEL, 1962). This review is based on tests with ten of these patients, eight of whom underwent a complete commissurotomy, i.e. the corpus callosum in its entirety, the anterior and hippocampal commissure, as well as the massa intermedia (when present) were sectioned in a single operation. In the other two patients (N. F., D. M.) only a partial division of the neocommissures, including the anterior two thirds of the callosum and the anterior commissure, was performed (case histories: BOGEN, 1969; GORDON et al., 1971).
New imaging techniques in cognitive neuroscience have produced a deluge of information correlating cognitive and neural phenomena. Yet our understanding of the inter-relationship between brain and mind remains hampered by the lack of a theoretical language for expressing cognitive functions in neural terms. We propose an approach to understanding operational laws in cognition based on principles of coordination dynamics that are derived from a simple and experimentally verified theoretical model. When applied to the dynamical properties of cortical areas and their coordination, these principles support a mechanism of adaptive inter-area pattern constraint that we postulate underlies cognitive operations generally.
In this paper we pursue the argument that where a group of muscles functions as a single unit the resulting coordinative structure, to a first approximation, exhibits behavior qualitatively like that of a force-driven mass-spring system. Data are presented illustrating the generative and context-independent characteristics of this system in tasks that require animals and humans to produce accurate limb movements in spite of unpredictable changes in initial conditions, perturbations during the movement and functional deafferentation. Analogous findings come from studies of articulatory compensation in speech production. Finally we provide evidence suggesting that one classically-defined source of information for movement, namely proprioception, may not be dimension-specific in its contribution to coordination and control.
In bimanual movements the amplitude of each hand's movement often depends on the concurrent amplitude of the other hand's movement such that both amplitudes become similar (amplitude coupling). We tested the hypothesis that the strength of amplitude coupling depends on the tempo of performance of a movement sequence, a hypothesis based on a model of bimanual coordination that holds that cross-talk occurs at the execution level as well as at the programming level. Subjects performed bimanual periodic arm movements on two digitizers. In nine conditions constant small, constant large, and alternating small and large amplitudes of each arm were orthogonally combined. Overall tempo was varied by instructing subjects to increase the tempo progressively by 10%. Clear tempo-dependent modulations of the amplitude were observed in movements with instructed constant amplitude when the other hand performed alternating amplitudes. The effect of the size of constant-amplitude movements on the mean amplitude of the other hand indicated cross-talk at the execution level. Cross-talk at the programming level was revealed by the dependence of the current amplitude on the change in the amplitude of the other hand in the preceding cycle. Finally, asymmetric cross-manual effects were observed.
Human handedness was investigated in a 1:1 interlimb rhythmic coordination in which consistent and inconsistent left-handed and right-handed individuals oscillated hand-held pendulums. Mean phase difference (φ
stable) and its standard deviation (
SDφ) were evaluated as functions of mode of coordination (in-phase vs anti-phase) and the symmetry conditions imposed by controlling the natural frequencies of the left and right pendulums. The dependencies of φ
stable and
SDφ on coordination mode and imposed symmetry were found to be systematically affected by handedness. The data were consistent with an elaboration of the established order parameter dynamics of interlimb rhythmic coordination. The elaboration includes additional 27π periodic terms that break the symmetry of those dynamics when the natural frequencies of the component rhythmic units are identical. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Two right-handed and 2 left-handed participants drew circles in the horizontal plane with both hands simultaneously in either a symmetrical or an asymmetrical mode, at their preferred rate or as fast as possible. During symmetrical movements, the hands showed frequency and phase synchronization at both rates. During fast asymmetrical movements, the hands showed increased phase difference and phase variability, as well as transitions to symmetrical movements, and cases of frequency decoupling. Large distortions of the hand trajectory were also observed under fast asymmetrical movements. Trajectory distortions and movement direction reversals were confined to the nondominant hand. Under the assumption that circular trajectories are generated by properly timed orthogonal oscillations along the
y-axis and the
x-axis, these findings are accounted for by the characteristics of coupling between homologous functional oscillators of the 2 body sides. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Previous studies have shown that activity of neuronal populations in the primary motor cortex (MI), processed by the population vector method, faithfully predicts upcoming movements. In our previous studies we found that single neurons responded differently during movements of one arm vs. combined movements of the two arms. It was, therefore, not clear whether the population vector approach could produce reliable movement predictions also for bimanual movements. This study tests this question by comparing the predictive quality of population vectors for unimanual and bimanual arm movements. We designed a bimanual motor task that requires coordinated movements of the two arms, in which each arm may move in eight directions, and recorded single unit activity in the MI of two rhesus (Macaca mulatta) monkeys during the performance of unimanual and bimanual arm movements. We analysed the activity of 212 MI cells from both hemispheres and found that, despite bimanual related activity, the directional tuning and preferred directions of most cells were preserved in unimanual and bimanual movements. We demonstrate that population vectors, constructed from the activity of MI cells, predict accurately the direction of movement both for unimanual and for bimanual movements even when the two arms move simultaneously in different directions.
We used a 61-channel electrode array to investigate the spatiotemporal dynamics of electroencephalographic (EEG) activity
related to behavioral transitions in rhythmic sensorimotor coordination. Subjects were instructed to maintain a 1:1 relationship
between repeated right index finger flexion and a series of periodically delivered tones (metronome) in a syncopated (anti-phase)
fashion. Systematic increases in stimulus presentation rate are known to induce a spontaneous switch in behavior from syncopation
to synchronization (in-phase coordination). We show that this transition is accompanied by a large-scale reorganization of
cortical activity manifested in the spatial distributions of EEG power at the coordination frequency. Significant decreases
in power were observed at electrode locations over left central and anterior parietal areas, most likely reflecting reduced
activation of left primary sensorimotor cortex. A second condition in which subjects were instructed to synchronize with the
metronome controlled for the effects of movement frequency, since synchronization is known to remain stable across a wide
range of frequencies. Different, smaller spatial differences were observed between topographic patterns associated with synchronization
at low versus high stimulus rates. Our results demonstrate qualitative changes in the spatial dynamics of human brain electrical
activity associated with a transition in the timing of sensorimotor coordination and suggest that maintenance of a more difficult
anti-phase timing relation is associated with greater activation of primary sensorimotor areas.
Bimanual coordination and the capability to parameterize the individual limb movements were examined in patients with Parkinson's disease (PD) as compared to healthy control subjects. In-phase and anti-phase patterns were performed while the individual limb movements were subjected to amplitude and loading manipulations. Findings showed that PD patients produced the bimanual configurations with lower degrees of phasing accuracy and consistency than control subjects, indicating an impairment at the global (coordinative) level of simultaneously produced movements. At the local (limb-specific) level, the imposed distances with and without loading were unaffected in PD patients as compared to control subjects, whereas cycle times were prolonged and depended on the task requirements. This illustrates a disturbance at the limb-specific level in complying with the execution of the submovements. The finding that movement slowness only became evident in the more complex conditions, suggests that it did not mainly represent a deficit in the execution of coordinated movements, but rather an inability to accommodate the motor output during stringent spatiotemporal task constraints.
New imaging techniques in cognitive neuroscience have produced a deluge of information correlating cognitive and neural phenomena. Yet our understanding of the inter-relationship between brain and mind remains hampered by the lack of a theoretical language for expressing cognitive functions in neural terms. We propose an approach to understanding operational laws in cognition based on principles of coordination dynamics that are derived from a simple and experimentally verified theoretical model. When applied to the dynamical properties of cortical areas and their coordination, these principles support a mechanism of adaptive inter-area pattern constraint that we postulate underlies cognitive operations generally.
Movement time varies as a function of amplitude and requirements for precision, according to Fitts' law, but when subjects
perform two-handed movements to targets of widely disparate difficulty they do so simultaneously. The hand moving to an "easy"
target moves more slowly to accommodate its "difficult" counterpart, yet both hands reach peak velocity and acceleration synchronously.
This result suggests that the brain produces simultaneity of action not by controlling each limb independently, but by organizing
functional groupings of muscles that are constrained to act as a single unit.
Models of basal ganglia function are described which encapsulate the principal pathophysiological mechanisms underlying parkinsonian akinesia on the one hand and abnormal involuntary movement disorders (dyskinesias) on the other. In Parkinson's disease, degeneration of the nigrostriatal dopamine system leads to overactivity of the striatopallidal projection to the lateral (external) segment of the globus pallidus. This causes inhibition of lateral pallidal neurons, which in turn project to the subthalamic nucleus. Disinhibition of the subthalamic nucleus leads to abnormal subthalamic overactivity and, as a consequence, overactivity of medial (internal) pallidal output neurons. Dyskinesias, such as are observed in Huntington's disease, levodopa-induced dyskinesia and ballism, share mechanistic features in common and are associated with decreased neuronal activity in both the subthalamic nucleus and the medial globus pallidus.
In many disciplines of science we deal with systems composed of many subsystems. A few examples, mainly taken from topics in this book, are listed in Fig. 1. Very often the properties of the large system can not be explained by a mear random superposition of actions of the subsystems. Quite on the contrary the subsystems behave in a well organized manner, so that the total system is in an ordered state or shows actions which one might even call purposeful. Furthermore one often observes more or less abrupt changes between disorder and order or transitions between different states of order. Thus the question arises, who are the mysterious demons who tell the subsystems in which way to behave so to create order, or, in a more scientific language, which are the principles by which order is created.
The hypothesis was tested that the strength of cross-manual effects of voluntary amplitude modulations in bimanual tasks increases when less preparation time is available during the execution of a sequence of movements. By means of the continuation procedure, various period durations (600, 800, 1200, and 1800 msec) of movement sequences were imposed. Subjects performed bimanual periodic arm movements on two digitizers: constant-amplitude movements (short or long) with the one hand, and movements of constant short or constant long amplitudes and movements of alternating short and long amplitudes with the other hand. Period-duration-dependent modulations of the amplitude were observed in movements of instructed constant amplitudes when the other hand performed alternating-amplitude movements, but not when the other hand performed constant-amplitude movements. Not only physical performance, but also the imaginary production of alternating-amplitude movements resulted in period-duration-dependent cross-manual effects, though reduced in size. The pattern of results is in agreement with a recently proposed two-level model of cross-manual effects according to which cross-talk can occur at the programming level as well as at the execution level.
The ipsilateral primary motor cortex (M1) plays a role in voluntary movement. In our studies, we used repetitive transcranial magnetic stimulation (rTMS) to study the effects of transient disruption of the ipsilateral M1 on the performance of finger sequences in right-handed normal subjects. Stimulation of the M1 ipsilateral to the movement induced timing errors in both simple and complex sequences performed with either hand, but with complex sequences, the effects were more pronounced with the left-sided stimulation. Recent studies in both animals and humans have confirmed the traditional view that ipsilateral projections from M1 to the upper limb are mainly directed to truncal and proximal muscles, with little evidence for direct connections to distal muscles. The ipsilateral motor pathway appears to be an important mechanism for functional recovery after focal brain injury during infancy, but its role in functional recovery for older children and adults has not yet been clearly demonstrated. There is increasing evidence from studies using different methodologies such as rTMS, functional imaging and movement-related cortical potentials, that M1 is involved in ipsilateral hand movements, with greater involvement in more complex tasks and the left hemisphere playing a greater role than the right.
Eleven right-handed subjects performed uni- and bimanual tapping tasks. Hemodynamic responses as measured with functional magnetic resonance imaging (fMRI) in the primary somato-motor cortex (SMC) showed that during bimanual activity the SMC contralateral to the hand taking the faster rate was more strongly activated than the SMC contralateral to hand taking the slower rate. There were no asymmetries, left SMC activation during the right fast/left slow tapping condition was comparable to the right SMC activation during the left fast/right slow condition. A given SMC showed similar activation levels for bimanual and unimanual activity (i.e. left SMC activation for right fast/left slow was similar to left SMC activation for the right fast unimanual condition). In contrast, a given supplementary motor area (SMA) showed significantly more activation for the bimanual than for the unimanual activity. In addition, an asymmetry was observed during bimanual activities: during the right fast/left slow activity, the left SMA showed more activation than the right SMA, but during the left fast/right slow activity, the right SMA was not significantly more activated than the left SMA. For unimanual activities, a clear rate effect (greater activation for faster rate) was seen in the SMC but not in the SMA.
BECAUSE of the multiple and varied aspects of Parkinsonism, the therapeutic approach has been exceedingly difficult. Most efforts have been directed toward symptomatic control of rigidity and tremor. The atropine-like drugs have been relatively successful in alleviating rigidity in patients able to tolerate adequate amounts.¹ Parsidol (10-[2-diethylamino-1-propyl] phenothiazine hydrochloride)² has been reasonably effective in some patients in reducing tremor, and by various drug combinations and the individualizing of dosages³ many Parkinsonian patients continue to lead active, useful lives.
A common complaint of the Parkinsonian patient is related, however, to fatigue and slowness in performing the chores of ordinary life. This is attributed to the interference caused by the muscle rigidity and tremor. In 50 patients with Parkinsonism, visual-motor reaction time tests have been routinely performed, and the values are close to normal in mild and moderately severe cases. In the course of observing a large number of
In order to study the role of the corpus callosum in two-handed coordination we tested callosotomy subjects while they attempted to initiate simultaneous discrete movements with both hands. We observed four split-brain patients, including one pre- and post-operatively, as well as normal and epileptic control subjects. Split-brain patients made button presses that were less synchronous than either normal or epileptic controls. Although split-brain patients' average performance did not always differ from control subjects, callosotomy resulted in a 3-fold increase in the variability with which `simultaneous' movements were initiated. The one subject tested pre- and post-callosotomy showed distinct changes in movement initiation synchrony after both the anterior and the posterior stages of the surgery. These changes suggest that anterior and posterior callosal fibres may make unique contributions to bimanual synchronization, depending on whether responses are self-initiated or in reaction to a visual stimulus. This study demonstrates that neural communication across anterior and posterior fibres of the corpus callosum strongly influences the temporal precision of bimanual coordination. Specifically, callosal transmission affects the degree of bilateral synchrony with which simple simultaneous hand and finger movements are initiated.
The present experiments addressed the learner's capability to perform different upper-limb actions simultaneously with the help of various sources of information feedback. An elbow flexion movement was made in the left limb together with a flexion-extension-flexion movement in the right limb. Interlimb interactions were assessed at the structural as well as the metrical level of movement specification during acquisition and retention. Despite a strong initial tendency for the limbs to be synchronized, findings revealed that Ss became gradually more successful in interlimb decoupling as a result of practice with augmented feedback. However, detailed knowledge of movement kinematics was no more effective than global outcome information for interlimb decoupling, indicating that knowledge of results may have more potential for acquiring multiple degree-of-freedom tasks than previously believed. Finally, the data support the general notion that learning new coordination tasks involves the suppression of preexisting preferred coordination tendencies, which is often a prerequisite for building new coordination modes.
The basal ganglia may be involved in bimanual co-ordination. Parkinson's disease (which impairs basal ganglia output) is clinically reported to cause difficulties in the performance of co-ordinated bimanual movements. Nevertheless, any bimanual co-ordination difficulties may be task specific, as experimental observations are equivocal. To infer the role of the basal ganglia in co-ordinating the two arms, this study investigated the bimanual co-ordination of patients with Parkinson's disease. Sixteen Parkinson's disease patients and matched control subjects performed a bimanual cranking task, at different speeds (1 and 2 Hz) and phase relationships. All subjects performed the required bimanual in-phase movement on a pair of cranks, at fast (2 Hz) and slow (1 Hz) speeds. However, the Parkinson's disease patients were unable to perform the asymmetrical anti-phase movement, in which rotation of the cranks differed by 180 degrees, at either speed; but instead reverted to the in-phase symmetrical movement. For Parkinson's disease patients, performance of the in-phase movement was more accurate and stable when an external timing cue was used; however, for anti-phase movement, the external cue accentuated the tendency for patients to revert to more symmetrical, in-phase movements.