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Handedness Consistency influences Bimanual Coordination: A behavioural and electrophysiological investigation

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... Three findings are relevant here. First, Kourtis, De Saedeleer, and Vingerhoets (2014) found that inconsistent-handers' performance on a task requiring simultaneous bimanual movements was not affected by task complexity, while consistent-handers were slower on more complex tasks. Second, Gorynia and Egenter (2000) found that inconsistent-handers had a greater affinity than did consistent-handers for making rapid, alternating bimanual movements. ...
... Because we utilized an existing data repository and did not have control over which measures were administered, we do not have consistency of hand preference data for the subjects in this study. We therefore do not know whether greater bimanual coordination was associated with greater inconsistency of hand preference in this study (although that relationship has been found elsewhere; Christman, 1993;Gorynia & Egenter, 2000;Kourtis et al., 2014). Consequently, we cannot make claims about whether bimanual coordination and consistency of hand preference are independent predictors of episodic memory or simply two manifestations of a common predictive factor. ...
... Furthermore, as we can only speculate as to why bimanual coordination would be negatively related to right LPFC thickness, we can offer an alternative explanation that draws on the known relationship between bimanual coordination and consistency of hand preference (Christman, 1993;Gorynia & Egenter, 2000;Kourtis et al., 2014). Recent studies (Arning et al., 2013;Robinson, Hurd, Read, & Crespi, 2016) have shown that inconsistency and consistency are associated with different polymorphisms of a gene thought to be involved in development of brain asymmetries (PCSK6, proprotein convertase subtilisin/ kexin type 6). ...
Article
Some people remember events more completely and accurately than other people, but the origins of individual differences in episodic memory are poorly understood. One way to advance understanding is by identifying characteristics of individuals that reliably covary with memory performance. Recent research suggests motor behavior is related to memory performance, with individuals who consistently use a single preferred hand for unimanual actions performing worse than individuals who make greater use of both hands. This research has relied on self-reports of behavior. It is unknown whether objective measures of motor behavior also predict memory performance. Here, we tested the predictive power of bimanual coordination, an important form of manual dexterity. Bimanual coordination, as measured objectively on the Purdue Pegboard Test, was positively related to correct recall on the California Verbal Learning Test-II and negatively related to false recall. Furthermore, MRI data revealed that cortical surface area in right lateral prefrontal regions was positively related to correct recall. In one of these regions, cortical thickness was negatively related to bimanual coordination. These results suggest that individual differences in episodic memory may partially reflect morphological variation in right lateral prefrontal cortex and suggest a relationship between neural correlates of episodic memory and motor behavior.
... It is this through the indirect link which an attentional asymmetry would drive adult handedness, linked by way of consistent selection biases which persist into unimanual variants of a multitude of tasks. Some tacit support for this proposition comes from Kourtis et al. (2014), who provided behavioral and electrophysiological evidence that performance in bimanual tasks with asymmetrical demands reflects the consistency, rather than the direction, of an individual's handedness. ...
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It is well established that the vast majority of the population favors their right hand when performing complex manual tasks. However, the developmental and evolutionary underpinnings of human manual asymmetries remain contentious. One often overlooked suggestion is that right handedness may stem from an asymmetrical bias in attention, with the right hand being allocated more attentional resources during bimanual tasks than the left hand (Peters, 1981). This review examines the evidence for attentional asymmetries during a variety of bimanual tasks, and critically evaluates the explanatory power of this hypothesis for explaining the depth and breadth of individual- and population-level manual asymmetries. We conclude that, while the attentional bias hypothesis is well-supported in adults, it requires further validation from a developmental perspective to explain the full breadth of adult manual laterality.
... These hemisphere specializations are believed to provide the basis for behavioral observations of complementary roles during bimanual coordination of the right (dominant) arm for reaching and manipulating and the left (non-dominant) arm for stabilizing [36,37]. Hand dominance has been shown to influence bilateral coordination in young adults, such that individuals with a reduced lateral preference demonstrate a bilateral performance advantage [38] and that arm specializations interfere with the performance of symmetrical tasks [39]. ...
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Although evidence exists that changes in sensorimotor function occur with aging, changes in the bilateral coordination of the upper extremities are less understood. Here, we review the behavioral and neural evidence of declines in bilateral coordination as well as the implications these deficits have on function and physical rehabilitation. We begin with an introduction to the two major forms of bilateral coordination, symmetric and non-symmetric, and their sub-groupings. After discussing the motor performance changes with age in symmetric tasks, we address age-related changes in motor lateralization that may affect the bilateral coordination of non-symmetric coordination. This is followed by a discussion of the contributions of cognitive, sensory, and cortical changes with age that influence and underlie bilateral motor performance. Finally, age-related changes in motor learning of bilateral movements are also considered. In general, most age-related changes are found in complex symmetric movements but, surprisingly, there is a dearth of information about changes in the more challenging and ubiquitous non-symmetric bilateral movements. Future investigations should focus on broadening the understanding of age-related changes in complex, functionally relevant bilateral movements, such that the real-world implications of these changes may be derived.
... Apart from the differences in the tasks of the right-hand dominant and left-hand dominant individuals, it is important to know to what extent the dominant and non-dominant hand control the BCT. It has been found in a study that regardless of the dominant hand side, those who could use their non-dominant hand in some specific tasks are superior in planning and organizing BCTs (8). Therefore, the present study was conducted with the objective to determine the effect of peripheral visual constraint on dominant and non-dominant hands on the performance of BCT. ...
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Abstract Introduction: The effect of central vision occlusion on two-hand coordination tasks is assessed in previous studies. However, the effect of peripheral vision on these tasks is not clearly identified; therefore, the purpose of this study was to investigate the effect of limitation of peripheral vision on two-hand coordination tasks. Materials and Methods: Seven right-handed and right eye-dominant girl students with a mean age of 24.00 ± 3.46 years participated in this study. Subjects tested under four experimental conditions including peripheral vision limitation of the position of right hand, left hand, and both hands, and no peripheral limitations of hand position in the two-handed Vienna coordination task with four tries for each condition. The data were analyzed using 1 × 4 repeated measures ANOVA. Results: All three conditions of visual peripheral limitation showed less errors than the conditions without visual limitation (P < 0.05). However, no significant difference was observed between four experimental conditions in the variable of total time (P > 0.05). Conclusion: It seems that the visual peripheral limitation, as an environmental constraint, may increase the focus and attention of people in the two-hand coordination task. Keywords: Visual occlusion, Environmental constraint, Hand, Cerebral dominance‬
... Recent neuroimaging techniques have made it possible to investigate the relationship between hand dominance and functional brain architecture. In this respect, functional magnetic resonance imaging (fMRI), electroencephalography (EEG), positron emission tomography (PET), magnetoencephalography (MEG), and transcranial magnetic stimulation (TMS) experiments have been recently utilized to study whether behavioral asymmetry (hand dominance) is associated with asymmetric neural tissue activation in the two hemispheres (Kim et al., 1993;Baraldi et al., 1999;Brouwer et al., 2001;Kobayashi et al., 2003;Pollok et al., 2006;Basso et al., 2006;Begliomini et al., 2008;Martin et al., 2011;Kourtis et al., 2014). Those studies have produced differing results in particular with regard to the activation of ipsilateral motor cortical areas in connection to the moving hand; the majority of fMRI studies has confirmed contralateral but also ipsilateral activation within motor-related areas (Kim et al., 1993;Baraldi et al., 1999;Kobayashi et al., 2003;Verstynen et al., 2005). ...
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Recording of neural activity during grasping actions in macaques showed that grasp-related sensorimotor transformations are accomplished in a circuit constituted by the anterior part of the intraparietal sulcus (AIP), the ventral (F5) and the dorsal (F2) region of the premotor area. In humans, neuroimaging studies have revealed the existence of a similar circuit, involving the putative homolog of macaque areas AIP, F5, and F2. These studies have mainly considered grasping movements performed with the right dominant hand and only a few studies have measured brain activity associated with a movement performed with the left non-dominant hand. As a consequence of this gap, how the brain controls for grasping movement performed with the dominant and the non-dominant hand still represents an open question. A functional magnetic resonance imaging (fMRI) experiment has been conducted, and effective connectivity (dynamic causal modeling, DCM) was used to assess how connectivity among grasping-related areas is modulated by hand (i.e., left and right) during the execution of grasping movements toward a small object requiring precision grasping. Results underlined boosted inter-hemispheric couplings between dorsal premotor cortices during the execution of movements performed with the left rather than the right dominant hand. More specifically, they suggest that the dorsal premotor cortices may play a fundamental role in monitoring the configuration of fingers when grasping movements are performed by either the right and the left hand. This role becomes particularly evident when the hand less-skilled (i.e., the left hand) to perform such action is utilized. The results are discussed in light of recent theories put forward to explain how parieto-frontal connectivity is modulated by the execution of prehensile movements.
... It has been described that handedness significantly influences bimanual coordination on the behavioral and physiological (shown by electroencephalography, EEG) level (Kourtis et al., 2014). However, as all our participants were right-handed, we conclude that none of the between group differences are influenced by handedness. ...
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The aim of this study was to examine whether older adults use the same task-specific brain activation patterns during two different bimanual hand movement tasks as younger adults. Functional magnetic resonance brain imaging was performed in 18 younger (mean age: 30.3 ± 3.6 years) and 11 older adults (62.6 ± 6.8 years) during the execution of cooperative (mimicking opening a bottle) or non-cooperative (bimanual pro-/supination) hand movements. We expected to see a stronger task-specific involvement of the secondary somatosensory cortex (S2) during cooperative hand movements in older compared to younger adults. However, S2 activation was present in both groups during the cooperative task and was only significantly stronger compared to the non-cooperative task in younger adults. In a whole brain-analysis, the contrast between older and younger adults revealed a hyperactivation of the bilateral dorsal premotor cortex (precentral gyrus), right thalamus, right frontal operculum, anterior cingulate cortex, and supplementary motor areas in older adults (p < 0.001), with some of them being visible after correcting for age. Age was positively associated with fMRI signal changes in these regions across the whole sample. Older adults showed reduced gray matter volume but not in regions showing task-related fMRI group differences. We also found an increase in functional connectivity between SMA, M1, thalamus, and precentral gyri in older adults. In contrast, younger adults showed hyperconnectivity between S2 and S1. We conclude that older compared to younger adults show age-related functional neuroplastic changes in brain regions involved in motor control and performance.
... These studies mainly rely on neurophysiological findings in the attempt to identify in humans a cortical network similar to that described in monkeys, in which the anterior intraparietal area (AIP), the ventral (F5), and the dorsal (F2) premotor cortices play a key role for the execution of grasping movements ( Murata et al., 1997; Rizzolatti and Luppino, 2001;Raos et al., 2004; see Castiello, 2005;Castiello and Begliomini, 2008 for reviews). The majority of these studies highlighted that grasping actions performed with one hand or the other are usually mirrored by an asymmetric recruitment of the two hemispheres in functional terms (left hand/right hemisphere vs. right hand/left hemisphere) ( Brouwer et al., 2001;Johnson-Frey et al., 2005;Basso et al., 2006;Pollok et al., 2006;Begliomini et al., 2008;Martin et al., 2011;Kourtis et al., 2014). However, in some cases ipsilateral activations within motor-related areas have also been reported ( Kim et al., 1993;Volkmann et al., 1998;Baraldi et al., 1999;Kobayashi et al., 2003;Verstynen et al., 2005). ...
Article
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Neurophysiological studies showed that in macaques, grasp-related visuomotor transformations are supported by a circuit involving the anterior part of the intraparietal sulcus, the ventral and the dorsal region of the premotor area. In humans, a similar grasp-related circuit has been revealed by means of neuroimaging techniques. However, the majority of “human” studies considered movements performed by right-handers only, leaving open the question of whether the dynamics underlying motor control during grasping is simply reversed in left-handers with respect to right-handers or not. To address this question, a group of left-handed participants has been scanned with functional magnetic resonance imaging while performing a precision grasping task with the left or the right hand. Dynamic causal modeling was used to assess how brain regions of the two hemispheres contribute to grasping execution and whether the intra- and inter-hemispheric connectivity is modulated by the choice of the performing hand. Results showed enhanced inter-hemispheric connectivity between anterior intraparietal and dorsal premotor cortices during grasping execution with the left dominant hand (LDH) (e.g., right hemisphere) compared to the right (e.g., left hemisphere). These findings suggest that that the left hand, although dominant and theoretically more skilled in left handers, might need additional resources in terms of the visuomotor control and on-line monitoring to accomplish a precision grasping movement. The results are discussed in light of theories on the modulation of parieto-frontal networks during the execution of prehensile movements, providing novel evidence supporting the hypothesis of a handedness-independent specialization of the left hemisphere in visuomotor control.
... However, even if gender is an important factor in the ability to bimanual coordination learning, it does not affect the present study, as the study group had the same number of women and men. It was demonstrated that limb domination affects bimanual coordination, since people with restricted domination show better results [50], and lateral specialization has a negative effect on the performance of symmetric tasks [51]. Also the results might be biased by diseases, especially of neurodegenerative origin, which means that the study conclusions can refer only to healthy, older people. ...
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Background The purpose of the study was to determine the impact of the performance of bimanual coordination tasks with specific characteristics on the changes in quality of coordination, musculoskeletal load of the upper limbs and cognitive functions. Methods and findings A group of 26 people aged 60–67 years performed 6 sessions of bimanual coordination training. Each session included set of tasks that varied depending on the shape in which the cursor moved, the coordination mode (in-phase, anti-phase, complex) and the tracking mode (imposed or freely chosen speed). Performance was assessed by: Error, Variability and Execution. The load of upper limb muscles was expressed with the value of the normalized EMG amplitude. Cognitive functions were evaluated using the Vienna Test System. The Variability and Error values obtained during the sixth training session decreased by more than 50% of the initial values. Tasks with freely chosen speed showed changes from 15% to 34% for Error and from 45% to 50% for Variability. For tasks with imposed speed and coordination mode anti-phase or complex it was between 51% and 58% for Error and between 58% and 68% for Variability. Statistically significant differences between load during the sixth training session compared to the first session occurred in three out of four muscles and were between 9% to 39%. There were statistically significant differences in motor time and no differences in variables describing attention and working memory. Conclusions Coordination mode is meaningful for improving coordination skills; tasks in the anti-phase and complex are recommended. Tracking mode also plays a role, tasks with an imposed cursor movement speed have greater potential to improve coordination skills than tasks with freely chosen. Improved control skills resulted in the reduction of upper limb musculoskeletal load. It can be assumed that an increase in coordination skills with the use of appropriate training can help to reduce musculoskeletal load.
... These hemisphere specializations are believed to provide the basis for behavioral observations of complementary roles during bimanual coordination of the right (dominant) arm for reaching and manipulating and the left (non-dominant) arm for stabilizing [36,37]. Hand dominance has been shown to influence bilateral coordination in young adults, such that individuals with a reduced lateral preference demonstrate a bilateral performance advantage [38] and that arm specializations interfere with the performance of symmetrical tasks [39]. ...
Article
Full-text available
Although evidence exists that changes in sensorimotor function occur with aging, changes in the bilateral coordination of the upper extremities are less understood. Here, we review the behavioral and neural evidence of declines in bilateral coordination as well as the implications these deficits have on function and physical rehabilitation. We begin with an introduction to the two major forms of bilateral coordination, symmetric and non-symmetric, and their sub-groupings. After discussing the motor performance changes with age in symmetric tasks, we address age-related changes in motor lateralization that may affect the bilateral coordination of non-symmetric coordination. This is followed by a discussion of the contributions of cognitive, sensory, and cortical changes with age that influence and underlie bilateral motor performance. Finally, age-related changes in motor learning of bilateral movements are also considered. In general, most age-related changes are found in complex symmetric movements but, surprisingly, there is a dearth of information about changes in the more challenging and ubiquitous non-symmetric bilateral movements. Future investigations should focus on broadening the understanding of age-related changes in complex, functionally relevant bilateral movements, such that the real-world implications of these changes may be derived.
... Our design challenged the typical (preferred) task distribution between the left and right hand as a faster tempo was required for the non-dominant hand in the 3:1 condition, exerting a change of focus of attention from the dominant to the nondominant hand, which led to increased performance difficulties. Deterioration of performance as a result of a less preferred compared to a preferred task allocation assignment may be an indication of the asymmetrical coupling between hands (Peters, 1985;Walter & Swinnen, 1990;Byblow et al., 1998;Kourtis et al., 2014). Interestingly, such asymmetrical performance is less common in highly skilled participants (Summers et al., 1993;Peper et al., 1995;Pressing et al., 1996), suggesting that the preference towards isofrequency movements and assignment of the more complex subtask to the dominant hand in non-isofrequency movements, can be overcome by training. ...
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The neural network and the task-dependence of (local) activity changes involved in bimanual coordination are well documented. However, much less is known about the functional connectivity within this neural network and its modulation according to manipulations of task complexity. Here, we assessed neural activity via high-density electroencephalography, focussing on changes of activity in the beta frequency band (~15–30 Hz) across the motor network in 26 young adult participants (19–29 years old). We investigated how network connectivity was modulated with task difficulty and errors of performance during a bimanual visuomotor movement consisting of dial rotation according to three different ratios of speed: an isofrequency movement (1:1), a non-isofrequency movement with the right hand keeping the fast pace (1:3), and the converse ratio with the left hand keeping the fast pace (3:1). To quantify functional coupling, we determined neural synchronization which might be key for the timing of the activity within brain regions during task execution. Individual source activity with realistic head models was reconstructed at seven regions of interest including frontal and parietal areas, among which we estimated phase-based connectivity. Partial least squares analysis revealed a significant modulation of connectivity with task difficulty, and significant correlations between connectivity and errors in performance, in particular between sensorimotor cortices. Our findings suggest that modulation of long-range synchronization is instrumental for coping with increasing task demands in bimanual coordination.
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Background: The manual dexterity of a surgeon is known to be related with surgical proficiency. Recently, as an objective measurement of surgical skills, inanimate methods using several types of simulators have been introduced. Using these simulators, we aimed to investigate the impact of manual dexterity on laparoscopic and robotic surgical proficiency. Materials and methods: Fellow surgeons, surgical residents, and medical students (n = 32) participated in this study. For the measurement of dexterity, the sums and differences of the right and left hand performance times for the Grooved Pegboard Test were used as an index of dexterity speed and ambidexterity, respectively. The performance times during three sessions of laparoscopic suturing using a D-box trainer and the performance scores during three sessions using two robotic suturing programs with different degrees of difficulty provided by the da Vinci(®) Skills Simulator™ (Intuitive Surgical Inc., Sunnyvale, CA) were analyzed according to the measured manual dexterity. Results: Manual dexterity was not a significant factor for performance time during laparoscopic suturing, which was more influenced by participants' surgical experiences. In robotic suturing, the performance score was impacted significantly by manual dexterity in terms of ambidexterity rather than dexterity speed. For an easy robotic suturing task, the gap of proficiency between the lower and higher ambidexterity groups was decreased successively with each of the three sessions. However, that gap in cases with a difficult task was maintained consistently throughout all three sessions. Conclusions: The degree of ambidexterity was an initial predictor for proficiency with simulated robotic suture. However, this relation could be lessened through a few sessions of training, although for a more difficult task further repetitions would be needed.
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We studied the potentially dissociable effects of handedness and consistency of hand preference on allocation of attention and movement planning. EEG was recorded from an equally balanced group of left- and right-handed participants with consistent or inconsistent hand preference. The participants viewed photos of graspable objects and responded to the direction of an arrow that was overlaid on the object 1000ms after object onset. Attention-related ERPs elicited between 100 and 250ms after object onset were primarily modulated by the participants’ handedness. On the other hand, ERPs related to late movement planning processes were modulated only by the consistency of hand preference. Our results suggest that the effects of the consistency of hand preference could be dissociated from those of handedness, the former influencing movement planning processes and the latter more related to allocation of attention.
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Bimanual coordination is an essential human function requiring efficient interhemispheric communication to produce coordinated movements. Previous research suggests a “bimanual advantage” phenomenon, where completing synchronized bimanual tasks results in less variability than unimanual tasks. Additionally, of hand dominance has been shown to influence coordinated performance. The present study examined the bimanual advantage in individuals with consistent and inconsistent handedness. It was predicted that participants with consistent handedness would not display a bimanual advantage unlike those with inconsistent handedness. Fifty-six young adults completed a finger-tapping paradigm in five conditions: unimanual tapping with either left or right hand, in-phase bimanual tapping, and out-of phase bimanual tapping led by either left or right hand. Results were not consistent with the hypothesis that participants with consistent handedness displayed the “bimanual advantage”. However, the “bimanual advantage” was not evident for the inconsistent handers when the temporal consistency was measured with either the left or right hand only. Overall, the “bimanual advantage” may be dependent upon consistency of hand preference, as well as the direction of hand dominance.
Chapter
In diesem Kapitel beschäftigen sich die Autorinnen mit den Grundlagen der Händigkeit. Zuerst wird geklärt, was Händigkeit ausmacht und wie sie definiert werden kann. Dann gehen die Autorinnen näher auf die Händigkeitsverteilung in der Bevölkerung ein und zeigen Unterschiede zwischen Links- und Rechtshändern auf. Es wird ein Überblick über die neuroanatomischen Strukturen im Gehirn gegeben, die die Händigkeit mitbegründen und beeinflussen. Daneben werden auch die zwei für die Händigkeitsbildung relevanten neurophysiologischen Phänomene der bimanuellen Kooperation und des Überkreuzens der Körpermitte beschrieben. Des Weiteren setzen sich die Autorinnen mit einigen Ursprungsfaktoren und Ursachen der Händigkeit auseinander und erläutern, welche Faktoren die Bildung der Händigkeit beeinflussen können (z. B. in Bezug auf Vererbung, Umwelteinflüsse vor, bei oder nach der Geburt oder pathologische Einflüsse). Schließlich wird erörtert, wie sich die Händigkeit im Lebensverlauf entwickelt.
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Handedness is a heritable trait, and left-handedness is related with increased fitness costs. Left-handedness persists, however, as a minority in every human population investigated. One explanation for this persistence has been put forward in the fighting hypothesis, which postulates that left-handers have a frequency-dependent benefit in fights. Support for this has been found in the finding that left-handedness is relatively frequent in populations with high homicide rates, according to estimates of left-handedness partly based on pictures and films made for a different purpose. We measured handedness based on hand preference in 10 ecologically relevant tasks in 621 subjects in the nonindustrial society of the Eipo (Papua, Indonesia) in which homicide rate was very high. This set of tests was validated in 198 Western students. Contrary to the prediction based on the fighting hypothesis, we did not find a high frequency of left-handedness or a difference between men (who participate in warfare) and women (who do not). These findings challenge the idea that fighting is the driving evolutionary force for the persistence of left-handedness in human populations. Furthermore, we found lower percentages of left- and mixed-handers compared to a Western population who executed the same tasks. Since left-handedness is associated with health problems, we suggest that in a society lacking Western health care, selection pressures against left-handedness may be more intense and therefore its frequency may be reduced.
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Summary About 90% of people are right-handed and 10% are left- handed. Handedness is associated with functional lateraliza- tion for cerebral dominance, and may also be associated with various types of psychopathology. Broadly speaking, the vast majority of humans seem to have been right-handed since the emergence of the genus Homo, some three to four million years ago. Likewise, in all societies studied, there is a large excess of right-handers. However, there have been few studies exploring the detailed history and geography of handedness, not least because adequate pre-twentieth century historical data are difficult to find, and very large sample sizes with consistent measurement methods are required for geograph- icalstudies.Thischapteroverviewsthevarioussetsofdatathat provide insight in handedness's history and geography. It is probable that about 8% to 10% of the population has probably been left-handed for at least the past 200000 years or so. Detailed data only began to become available for those born in the nineteenth century, and there is growing evidence that the rate of left-handedness fell precipitously during the Victorian period, reaching a nadirof about 3% in about 1895 or so, and then rising quite quickly until an asymptote is reached for those born after about 1945 to 1950, with 11% to 12% of men and 9% to 10% of women typically being left-handed in Western countries. Thesex ratioseems toremainconstant, not only during historical changes but also with geographical dif- ferences, and is presumably the result of a biological rather than a cultural process. Geographical differences in handedness are clearly appa- rent both between continents (as in Singh & Bryden's, 1994, comparison of Canada and India) and within continents: rates in Europe seeming to be highest in Britain, Holland, and Belgium, and falling away towards the east and south, and within countries, seen well in Stier's (1911) 1909 study of the German Army, in Leask and Beaton's (2007) study of the United Kingdom, and between the various states of the USA, in the very large Gilbert and Wysocki (1992) database. Ethnic differences in handedness are related to geographi- cal differences, with left-handedness generally being more common in White, Asian and Hispanic populations - a differ- ence seen both in the UK, and historically in the United States, wherethedifferencebetween ethnic groupshas grown smaller during the twentieth century, but was still present even for those born in the 1970s. Migration studies in the UK show that the lower rate of left-handedness in those from the Indian sub-continent is similar in those born in the UK and those born outside the UK, implying that genes rather than environ- ment are the primary source of the difference. Different rates of left-handedness can reflect either environ- mental or genetic differences between societies, and rates alone cannot distinguish the two processes. However, a math- ematical model shows that effects of different social pressure or gene frequencies can be distinguished if family data on handedness is available. That model suggests not only that geographicaldifferencesbut alsohistorical differences primar- ily reflect changes in gene frequency rather than direct social pressure.
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Handedness is the clearest example of behavioral lateralization in humans. It is not known whether the obvious asymmetry manifested by hand preference is associated with similar asymmetry in brain activation during movement. We examined the functional activation in cortical motor areas during movement of the dominant and nondominant hand in groups of right-handed and left-handed subjects and found that use of the dominant hand was associated with a greater volume of activation in the contralateral motor cortex. Furthermore, there was a separate relation between the degree of handedness and the extent of functional lateralization in the motor cortex. The patterns of functional activation associated with the direction and degree of handedness suggest that these aspects are independent and are coded separately in the brain.
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A growing body of evidence is reviewed showing that degree of handedness (consistent versus inconsistent) is a more powerful and appropriate way to classify handedness than the traditional one based on direction (right versus left). Experimental studies from the domains of episodic memory retrieval, belief updating/cognitive flexibility, risk perception, and more are described. These results suggest that inconsistent handedness is associated with increased interhemispheric interaction and increased access to processes localized to the right cerebral hemisphere.
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The relationship between vivid visual mental images and unexpected recall (incidental recall) was replicated, refined, and extended. In Experiment 1, participants were asked to generate mental images from imagery-evoking verbal cues (controlled on several verbal properties) and then, on a trial-by-trial basis, rate the vividness of their images; 30 min later, participants were surprised with a task requiring free recall of the cues. Higher vividness ratings predicted better incidental recall of the cues than individual differences (whose effect was modest). Distributional analysis of image latencies through ex-Gaussian modeling showed an inverse relation between vividness and latency. However, recall was unrelated to image latency. The follow-up Experiment 2 showed that the processes underlying trial-by-trial vividness ratings are unrelated to the Vividness of Visual Imagery Questionnaire (VVIQ), as further supported by a meta-analysis of a randomly selected sample of relevant literature. The present findings suggest that vividness may act as an index of availability of long-term sensory traces, playing a non-epiphenomenal role in facilitating the access of those memories.
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Brain-derived neurotrophic factor (BDNF) plays a critical role in brain development. A common single nucleotide polymorphism in the gene encoding BDNF (rs6265, Val66Met) affects BDNF release and has been associated with altered learning and memory performance, and with structural changes in brain morphology and corpus callosum integrity. BDNF Val66Met has more recently been shown to influence motor learning and performance. Some of the BDNF effects seem to be modulated by an individual's sex, but currently the relationship between BDNF and sex in the motor domain remains elusive. Here, we investigate the relationship between BDNF Val66Met genotype and an individual's sex in the motor system. Seventy-six healthy, previously genotyped, individuals performed a task in which the participant drew lines at different angles of varying difficulty. Subjects controlled the horizontal and vertical movement of the line on a computer screen by rotating two cylinders. We used this bimanual motor control task to measure contributions from both current motor function and the pre-existing interhemispheric connectivity. We report that BDNF genotype interacts with sex to influence the motor performance of healthy participants in this bimanual motor control task. We further report that the BDNF genotype by sex interaction was present in the more difficult trials only, which is in line with earlier findings that genetic effects may become apparent only when a system is challenged. Our results emphasize the importance of taking sex into account when investigating the role of BDNF genotype in the motor system.
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Many studies have suggested that each hand has a different special talent; however, there is a lack of data in the area of goal-directed bimanual hand coordination and its dependence on gender. The aim of this paper was to investigate gender-dependent bimanual speed-accuracy task performance. Twelve healthy young males and twelve healthy young females (all right-handed) performed protractile movements with both arms simultaneously by pushing joysticks toward two targets as quickly and accurately as possible. Though no significant difference was observed in the reaction time during a unimanual speed-accuracy task between the left and right hands as well as men and women, during a bimanual task, the reaction time of both the hands was significantly longer in women than men. There was no significant difference in the velocity of both the hands during a bimanual speed-accuracy task between men and women, while the accuracy of the left hand was significantly greater in men than women. There was no significant difference in intraindividual variability in the reaction time, maximal velocity, and path of movement between men and women as well as the left and right hands, but variability in the average velocity of the right hand both in women and men was significantly greater compared with their left hand. Whereas people typically look at the target location for a reaching movement, it is possible that two objects are simultaneously fixated.
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Research has shown that consistently right-handed individuals have poorer memory than do inconsistently right- or left-handed individuals under baseline conditions but more reliably exhibit enhanced memory retrieval after making a series of saccadic eye movements. From this it could be that consistent versus inconsistent handedness, regardless of left/right direction, is an important individual difference factor in memory. Or, more specifically, it could be the presence or absence of consistent right-handedness that matters for memory. To resolve this ambiguity, we compared consistent and inconsistent left- and right-handers on associative recognition tests taken after saccades or a no-saccades control activity. Consistent-handers exhibited poorer memory than did inconsistent-handers following the control activity, and saccades enhanced retrieval for consistent-handers only. Saccades impaired retrieval for inconsistent-handers. None of these effects depended on left/right direction. Hence, this study establishes handedness consistency, regardless of direction, as an important individual difference factor in memory.
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Handedness and eye-dominance are undoubtedly associated statistically, although a previous meta-analysis has found that the precise relationship is difficult to explain, with about 35% of right-handers and 57% of left-handers being left eye dominant. Of particular difficulty to genetic or other models is that the proportions are distributed asymmetrically around 50%. The present study asked whether this complicated pattern of association occurred because, following Peters, it is necessary to divide right-and left-handers into consistent handers (who write and throw with the same hand) and inconsistent handers (who write and throw with opposite hands). In an analysis of 10,635 subjects from questionnaire studies, 28.8% of left-handers and 1.6% of right-handers by writing were inconsistent for throwing. Our results also showed that writing hand and throwing hand both relate independently to eyedness, that throwing hand is somewhat more strongly associated with eyedness, and that the awkward asymmetry around 50% is now removed, 24.2% of consistent right-handers being left eye dominant compared with 72.3% of consistent left-handers, and 55.4% of inconsistent right-handers compared with 47.0% of inconsistent left-handers. We conclude that eyedness is phenotypically secondary to writing and throwing handedness. In our discussion we note that eyedness runs in families, we present new data suggesting that writing hand and throwing hand are co-inherited, and we argue that further data are now required to model properly the associations of writing hand, throwing hand, and eyedness, as well as probably also footedness and language dominance.
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The cortical representation of five simple hand and finger movements in the human motor cortex was determined in left- and right-handed people with whole-head magnetoencephalography. Different movements were found to be represented by spatially segregated dipolar sources in primary motor cortex. The spatial arrangement of neuronal sources for digit and wrist movements was nonsomatotopic and varied greatly between subjects. As an estimator of hand area size in primary motor cortex, we determined the smallest cuboid volume enclosing the five dipole sources within the left and right hemisphere of each subject. Interhemispheric comparison revealed a significant increase of this volume in primary motor cortex opposite to the preferred hand. This asymmetry was due to a greater spatial segregation of neuronal dipole generators subserving different hand and finger actions in the dominant hemisphere. Mean Euclidean distances between dipole sources for different movements were 10.7 +/- 3.5 mm in the dominant and 9.4 +/- 3.5 mm in the nondominant hemisphere (mean +/- SD; P = 0. 01, two-tailed t-test). The expansion of hand representation in primary motor cortex could not simply be attributed to a greater number of pyramidal cells devoted to each particular movement as inferred from current source amplitudes. The degree of hemispheric asymmetry of hand area size in the primary motor cortex was correlated highly with the asymmetry of hand performance in a standardized handedness test (r = -0.76, P < 0.01). These results demonstrate for the first time a biological correlate of handedness in human motor cortex. The expansion of hand motor cortex in the dominant hemisphere may provide extra space for the cortical encoding of a greater motor skill repertoire of the preferred hand.
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Motor system organization varies with handedness. However, previous work has focused almost exclusively on direction of handedness (right or left) as opposed to degree of handedness (strength). In the present study, we determined whether measures of interhemispheric interactions and degree of handedness are related to contra- and ipsilateral motor cortical representations. Participants completed a battery of handedness assessments including both handedness preference measures and behavioral measures of intermanual differences in dexterity, a computerized version of the Poffenberger paradigm (PP) to estimate interhemispheric transfer time (IHTT), and they underwent transcranial magnetic stimulation (TMS) mapping of both motor cortices while we recorded muscle activity from the first dorsal interosseous muscle bilaterally. A greater number of ipsilateral motor evoked potentials (iMEPs) were elicited in less lateralized individuals with the number of iMEPs correlated with IHTT. There were no relationships between handedness or lateralization of dexterity and symmetry of contralateral motor representations, although this symmetry was related to IHTT. Finally, IHTT was positively correlated with multiple measures of laterality and handedness. These findings demonstrate that degree of laterality of dexterity is related to the propensity for exhibiting iMEPs and the speed of interhemispheric interactions. However, it is not clear whether iMEPs are directly mediated via ipsilateral corticospinal projections or are transcallosally transmitted.
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As compared with their prevalence in the general population, left-handers are overrepresented in the expert domain of many interactive sports. This study examined to what extent this is due to negative perceptual frequency effects--that is, whether the greater frequency of tennis matches with right-handed opponents makes it possible to discriminate the stroke movements of right-handed players more precisely. Fifty-four right-handed and 54 left-handed males in three equal-sized groups of varying levels of tennis expertise (national league experts, local league intermediates, and novices) completed a tennis anticipation test in which they had to predict the subsequent direction of an opponent's temporally occluded tennis strokes on a computer screen. The results showed that all three groups were better at predicting the direction of strokes by right-handed players. This supports the hypothesis that the overrepresentation of left-handers in the expert domain is partly due to perceptual frequency effects.
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Since prehistoric times, left-handed individuals have been ubiquitous in human populations, exhibiting geographical frequency variations. Evolutionary explanations have been proposed for the persistence of the handedness polymorphism. Left-handedness could be favoured by negative frequency-dependent selection. Data have suggested that left-handedness, as the rare hand preference, could represent an important strategic advantage in fighting interactions. However, the fact that left-handedness occurs at a low frequency indicates that some evolutionary costs could be associated with left-handedness. Overall, the evolutionary dynamics of this polymorphism are not fully understood. Here, we review the abundant literature available regarding the possible mechanisms and consequences of left-handedness. We point out that hand preference is heritable, and report how hand preference is influenced by genetic, hormonal, developmental and cultural factors. We review the available information on potential fitness costs and benefits acting as selective forces on the proportion of left-handers. Thus, evolutionary perspectives on the persistence of this polymorphism in humans are gathered for the first time, highlighting the necessity for an assessment of fitness differences between right- and left-handers.
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The coordination of movement between the upper limbs is a function highly distributed across the animal kingdom. How the central nervous system generates such bilateral, synchronous movements, and how this differs from the generation of unilateral movements, remain uncertain. Electrophysiologic and functional imaging studies support that the activity of many brain regions during bimanual and unimanual movement is quite similar. Thus, the same brain regions (and indeed the same neurons) respond similarly during unimanual and bimanual movements as measured by electrophysiological responses. How then are different motor behaviors generated? To address this question, we studied unimanual and bimanual movements using fMRI and constructed networks of activation using Structural Equation Modeling (SEM). Our results suggest that (1) the dominant hemisphere appears to initiate activity responsible for bimanual movement; (2) activation during bimanual movement does not reflect the sum of right and left unimanual activation; (3) production of unimanual movement involves a network that is distinct from, and not a mirror of, the network for contralateral unimanual movement; and (4) using SEM, it is possible to obtain robust group networks representative of a population and to identify individual networks which can be used to detect subtle differences both between subjects as well as within a single subject over time. In summary, these results highlight a differential role for the dominant and non-dominant hemispheres during bimanual movements, further elaborating the concept of handedness and dominance. This knowledge increases our understanding of cortical motor physiology in health and after neurological damage.
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In a set of three experiments, we show that after an auditory "go" signal, subjects simultaneously initiate and terminate two-handed movements to targets of widely disparate difficulty. This is the case when the movements required are (a) lateral and away from the midline of the body (Experiment 1), (b) toward the midline of the body (Experiment 2), and (c) in the forward direction away from the body midline (Experiment 3). Kinematic data obtained from high-speed cinematography (200 frames/sec) point to a tight coordinative coupling between the two hands. Although the hands move at entirely different speeds to different points in space, times to peak velocity and acceleration are almost perfectly synchronous. We believe that the brain produces simultaneity of action as the optimal solution for the two-handed task by organizing functional groupings of muscles (coordinative structures) that are constrained to act as a single unit.
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Many voluntary movements involve coordination between the limbs. However, there have been very few attempts to study the neuronal mechanisms that mediate this coordination. Here we have studied the activity of cortical neurons while monkeys performed tasks that required coordination between the two arms. We found that most neurons in the primary motor cortex (MI) show activity specific to bimanual movements (bimanual-related activity), which is strikingly different from the activity of the same neurons during unimanual movements. Moreover, units in the supplementary motor area (SMA; the area of cortex most often associated with bimanual coordination) showed no more bimanual-related activity than units in MI. Our results challenge the classic view that MI controls the contralateral (opposite) side of the body and that SMA is responsible for the coordination of the arms. Rather, our data suggest that both cortical areas share the control of bilateral coordination.
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For years we have known that cortical neurons collectively have synchronous or oscillatory patterns of activity, the frequencies and temporal dynamics of which are associated with distinct behavioural states. Although the function of these oscillations has remained obscure, recent experimental and theoretical results indicate that correlated fluctuations might be important for cortical processes, such as attention, that control the flow of information in the brain.
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Most people are right-handed, preferring the right hand for skilled as well as unskilled activities, but a notable proportion are mixed-handed, preferring to use the right hand for some actions and the left hand for others. Assuming a structural/functional correlation in the motor system we tested whether asymmetries in hand performance in consistent right and left handers as well as in mixed handers are associated with anatomical asymmetries in the motor cortex. In vivo MR morphometry was used for analyzing interhemispheric asymmetry in the depth of the central sulcus in the region of cortical hand representation of 103 healthy subjects. Subjects were tested both for hand preference and hand performance. As expected, left-right differences in hand performance differed significantly between consistent right, consistent left and mixed handers and were independent on gender. Male consistent right handers showed a significant deeper central sulcus on the left hemisphere than on the right. Anatomical asymmetries decreased significantly from male consistent right over mixed to consistent left handers. Sixty two per cent of consistent left handers revealed a deeper central sulcus on the right than on the left hemisphere, but for the group as a whole this rightward asymmetry was not significant. No interhemispheric asymmetry was found in females. Thus, anatomical asymmetry was associated with handedness only in males, but not in females, suggesting sex differences in the cortical organization of hand movements.
Article
Most people are right-handed, preferring the right hand for skilled as well as unskilled activities, but a notable proportion are mixed-handed, preferring to use the right hand for some actions and the left hand for others. Assuming a structural/functional correlation in the motor system we tested whether asymmetries in hand performance in consistent right and left handers as well as in mixed handers are associated with anatomical asymmetries in the motor cortex. In vivo MR morphometry was used for analyzing interhemispheric asymmetry in the depth of the central sulcus in the region of cortical hand representation of 103 healthy subjects. Subjects were tested both for hand preference and hand performance. As expected, left-right differences in hand performance differed significantly between consistent right, consistent left and mixed handers and were independent on gender. Male consistent right handers showed a significant deeper central sulcus on the left hemisphere than on the right. Anatomical asymmetries decreased significantly from male consistent right over mixed to consistent left handers. Sixty two per cent of consistent left handers revealed a deeper central sulcus on the right than on the left hemisphere, but for the group as a whole this rightward asymmetry was not significant. No interhemispheric asymmetry was found in females. Thus, anatomical asymmetry was associated with handedness only in males, but not in females, suggesting sex differences in the cortical organization of hand movements.
Article
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.
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An 81-electrode system is described which is designed for topographic studies of spontaneous and evoked EEG activities. This method combines the standard leads of the International 10-20 System with supplementary electrodes applied midway between leads of the 10-20 system or electrodes in turn situated between 10-20 leads. Auxiliary electrode designations refer to the underlying brain areas and to adjacent leads of the 10-20 method. The utilization of this '10% system' is suggested to promote standardization.
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This article reports an experimental study designed to test the hypothesis that self-awareness plays a causal role in the experience of shame but not guilt. The effects of a self-focus manipulation on shame and guilt proneness were assessed by having male and female participants complete an internal vs. external focus of attention writing task and then complete the Test for Self-conscious Affect. Results indicated that heightened self-focus increased shame proneness but not guilt proneness for women but did not have parallel effects for men. Implications of these results for understanding self-conscious emotions are briefly discussed.
Article
The ubiquitous and persistent handedness polymorphism in humans requires an evolutionary explanation. It has been suggested that left-handers have a frequency-dependent advantage during a fight, such that this advantage decreases when their frequency increases. Many independent studies are providing data from interactive sports (a specific class of fights), and are very supportive of the fighting hypothesis. The only intercultural study on traditional societies is also consistent with the fighting hypothesis, although it has not yet been replicated. The frequencies of left-handers in the few remaining violent societies are likely to be rapidly decreasing, due to Western colonization (long-range weapons, religion, and money market) dramatically affecting the frequency-dependent selection associated with handedness. Clearly, more data are urgently needed outside the Western influence.
Article
Potentials recorded from the scalp of human subjects preceding voluntary finger movements may be devided into 3 components:1. a slowly increasing surface negative readiness potential which starts about 850 msec before movement and is bilaterally symmetrical over the pre- and post-central region with a maximum at the vertex; 2. a pre-motion positivity which is also bilaterally symmetrical and starts about 86 msec before the onset of EMG; 3. a surface negative motor potential which starts about 56 msec before the onset of movement in the EMG and has its maximum over the contralateral precentral hand area.
Article
Ten subjects were instructed to squeeze a dynamometer in a prescribed manner in order to assess the effects of motor preparation on event-preceding brain potentials. Right and left hand responses were required in 5 different experimental conditions allowing different degrees of advance preparation. Six channels of EEG (F3, F4, C3′, C4′, P3, P4) and two channels of EMG were digitized over a 3000 msec epoch, and response-locked averages were computed. Event-preceding negative potentials were evident well in advance of movement if the subject was informed of the timing of the response. These premovement potentials were asymmetrical on the scalp (contralaterally dominant at the central sites) if the subject knew which hand would be required to respond. Thus, we conclude that the appearance and asymmetry of these potentials reflect preparation to execute specific motor acts.
Article
A total of 22 right-handed and 22 left-handed participants performed tasks on a well-established test of manual dexterity in addition to completing the Waterloo Handedness Questionnaire. Analysis of Variance revealed that left-handers performed significantly better on the Purdue pegboard test when the task relied on the co-ordination of both the left and right hands. Multiple regression analysis indicated that the Purdue pegboard assembly task is a predictor of self-reported hand preference and of handedness when classified by the Waterloo Handedness Questionnaire. Left-handers showed a smaller performance difference between hands, suggesting an advantage in using their non-preferred hand, although this did not lead to a better performance on a bimanual placement task. These results suggest that left-handers perform more proficiently when hand actions have to be alternated in completing a task. The superior performance of the non-preferred hand in left-handers might be explored to develop future behavioural predictors of handedness.
Article
Annett (1970a) described 283 subjects classified for hand preference and measured for the movement time of each hand on a peg moving task. A new sample of 804 subjects has been examined and classified as before. The mean differences between hands for each preference group are very similar in both samples. Hand preference can be regarded as anchored to an objective measure of manual skill. Both preference and skill are continuously distributed variables, not discrete ones. The quest for the ‘essence’ of left handedness should be replaced by studies of the characteristics of the distributions involved and of the criteria used to identify segments of the distributions.
Article
Movement-related potentials (MRPs) were recorded from subdural electrodes chronically implanted in the interhemispheric fissure in two patients being evaluated for epilepsy surgery. Different types of movements (finger, foot, tongue and vocalization) were executed. Foot movements elicited a clearly defined, well-localized slow negativity or positivity (Bereitschaftspotential, BP) preceding electromyogram (EMG) onset These BPs were seen from the contralateral primary motor foot area and also from bilateral supplementary motor areas (SMAs) with equivalent amplitudes and temporal evolutions. A steeper potential [negative slope (NS')] occurred about 300 ms before EMG onset and the motor potential (MP) started 100 ms before EMG onset Negative slopes and MPs also arose from the contralateral primary motor area as well as from the bilateral SMAs. Finger movements elicited well-localized BPs and NS' which were generated from the bilateral SMAs, but were of higher amplitude on the contralateral SMA. Motor potentials started 50 ms prior to EMG onset and arose exclusively from the contralateral SMA. Tongue protrusions and vocalizations also elicited BP, NS' and MP which were seen in the bilateral SMAs. Movement-related potentials for different types of movements had a somatotopic distribution in the SMA, which was consistent with the SMA somatotopic organization defined by electrical simulation. Movement-related potentials for tongue movements and vocalization had a similar distribution and waveform. It was concluded that bilateral SMAs generate well-defined MRPs consistent with the assumption that the SMA plays a significant role in the organization of voluntary movements. However, the MRPs from the bilateral SMAs do not have characteristics which are different from those of the primary motor area. This suggests the hypothesis of ‘supplementary’ function for SMA, and does not support the hypothesis of ‘supramotor’ function.
The present study was aimed at investigating the effect of inertial loading on movement-related potentials (MRPs) recorded from the scalps of normal subjects while performing finger movements. Two experiments were performed. Experiment 1. MRPs preceding and accompanying the execution of voluntary, unilateral finger movements were investigated in 8 subjects under the 3 experimental conditions of: no inertial load, small inertial load (250 g), and large inertial load (400 g). A significant effect of the inertial load on Bereitschaftspotential (BP) amplitude was observed for the 100 msec period preceding movement onset (BP -100 to 0) at precentral electrode sites and following movement onset (N0 to 100) at both precentral and parietal electrode sites. Pairwise comparisons revealed that significant effects were due to differences between the loading and non-loading conditions and not for different amounts of loading. No significant differences were observed for BP onset or early BP amplitudes, indicating that scalp negativity immediately prior to, and during, movement onset is primarily influenced by conditions of inertial loading. Experiment 2. This experiment examined the effect of inertial loading on MRPs for bilateral, simultaneous voluntary finger movements in 10 subjects under conditions of: no inertial load, inertial load applied separately to the left and right fingers, and with identical inertial loads applied to both fingers. No significant effect of inertial load on MRP amplitude was observed. These results are contrasted with those of experiment 1 which show significant effects of inertial loading for unilateral movements and are interpreted in terms of the hypothesis that bilateral movement organization involves 'higher' aspects of motor control than those reflecting adjustment to conditions of inertial loading.
Article
Fifty-three left-handers with consistent left-hand preferences (CLH), 65 left-handers with inconsistent hand preferences (ILH), and 57 right-handers (RH) were given unimanual and bimanual performance tests involving skill, speed, and strength as well as tests of articulatory speed and verbal fluency. Contrary to claims in the current literature (Ponton, 1987), CLHs and ILHs do not differ in quality and speed of performance, but, in some tests, they do show asymmetries in opposite directions. Thus, when left-handers are treated as a combined group, the faulty impression of a lack of between-hand asymmetries arises. The results suggest that a distinction between CLHs and ILHs yields subgroups with reliably different and distinctive performance patterns which are not trivially attributable to differences in strength of lateralization. CLHs behave much like mirror image RHs, whereas ILHs show a dissociation between strength, fine manual skill, attentional asymmetries.
Article
The possibility that incomplete speech lateralization might be related to reduced articulatory speed was investigated in two studies with normal, young adults. Contrary to expectations, speech was produced faster by ambidextrous subjects than by either strongly left- or strongly right-handed subjects under a number of conditions. However, there were no differences in speech lateralization between these groups when lateralization was measured using dichotic listening scores. In a second study, the superiority of ambidextrous subjects was found to extend to certain manual movement tasks as well.
Article
The need for a simply applied quantitative assessment of handedness is discussed and some previous forms reviewed. An inventory of 20 items with a set of instructions and response- and computational-conventions is proposed and the results obtained from a young adult population numbering some 1100 individuals are reported. The separate items are examined from the point of view of sex, cultural and socio-economic factors which might appertain to them and also of their inter-relationship to each other and to the measure computed from them all. Criteria derived from these considerations are then applied to eliminate 10 of the original 20 items and the results recomputed to provide frequency-distribution and cumulative frequency functions and a revised item-analysis. The difference of incidence of handedness between the sexes is discussed.
Article
Right, mixed and left handers are found in binomial proportions in seven samples of varied subjects whose lateral prefernces were ascertained by several methods. These proportions have been obtained in previous studies of humans and animals when the performance of several actions has been recorded in complete samples and when consistent right and left subjects have been separated from those of mixed usage.
A new off-line procedure for dealing with ocular artifacts in ERP recording is described. The procedure (EMCP) uses EOG and EEG records for individual trials in an experimental session to estimate a propagation factor which describes the relationship between the EOG and EEG traces. The propagation factor is computed after stimulus-linked variability in both traces has been removed. Different propagation factors are computed for blinks and eye movements. Tests are presented which demonstrate the validity and reliability of the procedure. ERPs derived from trials corrected by EMCP are more similar to a 'true' ERP than are ERPs derived from either uncorrected or randomly corrected trials. The procedure also reduces the difference between ERPs which are based on trials with different degrees of EOG variance. Furthermore, variability at each time point, across trials, is reduced following correction. The propagation factor decreases from frontal to parietal electrodes, and is larger for saccades than blinks. It is more consistent within experimental sessions than between sessions. The major advantage of the procedure is that it permits retention of all trials in an ERP experiment, irrespective of ocular artifact. Thus, studies of populations characterized by a high degree of artifact, and those requiring eye movements as part of the experimental task, are made possible. Furthermore, there is no need to require subjects to restrict eye movement activity. In comparison to procedures suggested by others, EMCP also has the advantage that separate correction factors are computed for blinks and movements and that these factors are based on data from the experimental session itself rather than from a separate calibration session.
To clarify the differences of movement-related potentials (MRPs) among ipsilateral, contralateral and simultaneous bilateral movements, MRPs with finger, thumb or foot movements were recorded from subdural electrodes chronically implanted on the supplementary motor area (SMA) in 3 patients, and also from the primary sensorimotor area in two of them being evaluated for epilepsy surgery. As a result: (1) SMA generated clear pre-movement potentials regardless of the type of movement. Its amplitude was almost identical between contralateral and bilateral movements except for the motor potential (MP). The pre-movement potentials associated with ipsilateral movements were relatively smaller than those with contralateral or bilateral movements. (2) The primary sensorimotor area generated clear pre-movement potentials in contralateral and bilateral movements with similar amplitude. With ipsilateral hand movements, however, only a small Bereitschaftspotential (BP) and no negative slope (NS') or MP was seen, and ipsilateral foot movements were not preceded by any BP. It is, therefore, most likely that, as far as the preparation for simple voluntary self-paced movement is concerned, the SMA plays an equally important role in unilateral and bilateral movements, whereas the primary sensorimotor area is involved predominantly in the preparation of contralateral movements.
The existence of the mu rhythm and its general anatomical and physiological relationships are well known. There are few data, however, regarding the details of its anatomical and physiological specificity. We implanted fronto-temporal subdural electrode grids in 9 patients with intractable epilepsy to facilitate their surgical management. A 7-11 Hz cortical mu rhythm was observed in 5-16 electrodes located over the sensorimotor cortex as mapped by electrical stimulation. The mu rhythm was blocked by contralateral face and arm movements, passive movements of contralateral arm, and by ipsilateral arm movements. There was correspondence between the body area movement of which blocked the mu at a given site and the body region that was affected by stimulation at the same site. Power spectral analysis showed an overall decrease in power in all frequency bands. This was less prominent in the 14-100 Hz band resulting in a relative increase in high frequency power in association with movement. We conclude that both the presence and blocking of mu rhythm are specific to the somatic representation of the cortex from which it is recorded. Its functional significance may be similar to other sensory rhythms like the occipital alpha rhythm.
Article
Three groups of right-handers were identified using the Edinburgh Handedness Inventory. Exclusive strong right-handers (Rs: N = 18) reported that they always used the right hand for eight or more of the 10 activities, and usually used the right hand for the remainder. Exclusive weak right-handers (Rw: N = 15) usually used the right hand for three or more activities, and always used the right hand for the remainder. Predominant right-handers (Rp: N = 18) preferred the right hand for most items, but used the left hand for at least one activity. These groups did not differ on three measures of relative skill of the two hands: peg-moving, tapping and dotting. Groups Rs and Rw were also indistinguishable in terms of the hand used for reaching for cards placed in different spatial positions. However, the reaching measure did discriminate group Rp, which included some individuals who reached predominantly with the left hand. It is concluded that preference batteries should quantify degree of hand preference in terms of the number of activities for which a preference is shown, ignoring the distinction between 'usually' and 'always'. The behavioural reaching measure shows promise as a method for providing a unitary scale of hand preference.
Article
Spontaneous EEG can display spatio-temporal patterns of desynchronized or synchronized alpha band activity. Event-related desynchronization (ERD) of rhythms within alpha and lower beta bands is characteristic of activated cortical areas ready to process information or to prepare a movement, while event-related synchronization (ERS) in the same frequency bands can be seen as an electrophysiological correlate of resting or idling cortical areas. EEG was investigated over primary sensorimotor and premotor areas during discrete hand and foot movements. ERD was found over the primary hand area during finger movement and over the primary foot area during toe movement. The former was observed in every subject, the latter was more difficult to find. From these results it can be speculated that each primary sensorimotor area has its own intrinsic rhythm, which becomes desynchronized when the corresponding area is activated. ERS, in the form of an enhanced mu rhythm on electrodes overlying the primary hand area, was observed not only during visual processing but also during foot movement. In both cases, the hand area is not needed to perform a task and, therefore, can be considered to be in an idling state. The supplementary motor area (SMA) also plays an important role in preparation and planning of movement. It is demonstrated that this area also displays rhythmic activity within the alpha band, that is both linearly and non-linearly phase coupled to the intrinsic (mu) rhythm of the primary hand area. With planning and preparation of movement, this SMA rhythm is desynchronized and also the degree of coupling between the two areas decreases.
Article
We modelled the responses of human primary sensorimotor areas and supplementary motor area to simple, self-initiated unilateral and simultaneous bilateral middle finger movements using a novel high-resolution electroencephalography technology. The results support the view that these cortical motor areas are involved in parallel and present similar activity in the preparation, initiation, and execution of the contralateral and bilateral movements. Furthermore, the left primary sensorimotor area (dominant hemisphere) appears to be activated more than the right primary sensorimotor area during the preparation and performance of the ipsilateral movements.
Article
The aim of this study was to analyze how functional activation in the supplementary motor area (SMA) and sensorimotor cortex (SMC) is related to bimanual coordination using functional magnetic resonance imaging. Subjects included 24 healthy volunteers, 15 of whom were right-handed and 9 left-handed. Three kinds of activation tasks, all of which required the repetitive closing and opening of a fist, were performed: unimanual movement of the nonpreferred hand (task A); simultaneous, agonistic movement of both hands (task B); simultaneous, antagonistic movement of both hands (task C). The SMA activation during task C was more pronounced than that during the other two tasks for right and left handers. The results suggested that the activation of the SMA, at least during a simple motion used in the present study, was little influenced by whether the motion was unimanual or bimanual but instead how the bimanual motion was composed of the motion element of a single hand. The SMC activation during task C was significantly larger than that during task B, whereas hemispheric differences in the activation were not found. This indicated that the complexity of the bimanual movement also affected the SMC activation.
Article
An internally or externally paced event results not only in the generation of an event-related potential (ERP) but also in a change in the ongoing EEG/MEG in form of an event-related desynchronization (ERD) or event-related synchronization (ERS). The ERP on the one side and the ERD/ERS on the other side are different responses of neuronal structures in the brain. While the former is phase-locked, the latter is not phase-locked to the event. The most important difference between both phenomena is that the ERD/ERS is highly frequency band-specific, whereby either the same or different locations on the scalp can display ERD and ERS simultaneously. Quantification of ERD/ERS in time and space is demonstrated on data from a number of movement experiments.
Article
Movement-related potentials (MRPs) and event-related desynchronization (ERD) of alpha rhythm were investigated with an advanced high-resolution electroencephalographic technology (128 channels, surface Laplacian estimate, realistic head modeling). The working hypothesis was that MRPs and alpha ERD reflect different aspects of sensorimotor cortical processes. Both MRPs and alpha ERD modeled the responses of primary sensorimotor (M1-S1), supplementary motor (SMA), and posterior parietal (PP, area 5) areas during the preparation and execution of unilateral finger movements. Maximum responses were modeled in the contralateral M1-S1 during both preparation and execution of the movement. The SMA and PP responses were modeled mainly from the MRPs and alpha ERD, respectively. The modeled ipsilateral M1-S1 responses were larger and stronger in the alpha ERD than MRPs. These results may suggest that alpha ERD reflects changes in the background oscillatory activity in wide cortical sensorimotor areas, whereas MRPs represent mainly increased, task-specific responses of SMA and contralateral M1-S1.
Article
Intermanual coordination assessed by alternating finger tapping and finger-tapping asymmetry were investigated in 105 healthy right- and 105 left-handers and related to handedness, familial sinistrality and lateral preferences (in hand-clasping, arm-folding and eyedness). Compared to right-handers, left-handers with less pronounced left-hand preferences (Subgroup B) showed higher values in intermanual coordination and lower values in finger-tapping asymmetry. Moreover, familial sinistrality and eyedness interacted with handedness effects. While in right-handers intermanual coordination was significantly higher in subjects with dominant left eye, in left-handers of the Subgroup B it was somewhat higher in those with dominant right eye. Higher values in intermanual coordination and reduced asymmetry in finger tapping may be associated with a greater bihemispheric control and better performance in fast bimanual movements.
Article
The goal of this study is to investigate the reactivity of central rhythms in the alpha band during self-paced voluntary finger and foot movement and to give an answer to the question, whether different types of mu rhythms exist. The effect of self-paced, voluntary finger and foot movement was studied in a group of 12 right-handed healthy volunteers. The EEG was recorded from a grid of 34 electrodes placed over sensorimotor areas with inter-electrode distances of approximately 2.5 cm. The event-related desynchronization (ERD) was quantified in the 8-10 and 10-12 Hz bands. Both frequency components are blocked prior to and during movement and therefore, they have to be considered as mu rhythms. The lower frequency component results in a widespread movement-type non-specific ERD pattern, whereas the upper frequency component shows a more focused and movement-type specific pattern, clearly different with finger and foot movement. The distinct reactivity patterns provide evidence for the existence of two types of mu rhythms, a somatotopically non-specific lower frequency mu rhythm and a somatotopically specific mu rhythm characteristically found in the upper alpha frequency band.
Article
To examine how the differences in the sequences of brain activation during the go/no-go delayed response choice reaction time (RT) task are reflected into two concurrent methods of measuring brain electrical activity, the alpha band event-related desynchronization (alpha ERD) and the contingent negative variation (CNV). alpha ERD and CNV were calculated using appropriate techniques from the same samples of electroencephalographic activity recorded during performance of a cued choice go/no-go delayed response RT task (i.e. S1 (go/no-go)--S2 paradigm) in 8 healthy subjects. All segments of the CNV traces were different in the go and the no-go conditions. The go CNV traces displayed a typical pattern of slow rising negativity reflecting the build-up of attentional resources necessary for adequate performance of the task. On the other hand, the no-go traces remained close to zero reflecting the 'withdrawal' of further preparation after evaluation of S1. During the same period, both go and no-go ERD traces showed a gradual decrease in alpha band power (desynchronization) that was evident until shortly before the presentation of S2. It was only in the 500 ms before S2 presentation that there was any indication that the go and no-go ERD traces were different, but this did not reach statistical significance. Our data show that the pattern of the go/no-go difference in alpha ERD traces does not correspond to the pattern that can be seen in the CNV traces. This suggests that there is no direct coupling of CNV and alpha ERD, most probably because they measure different aspects of cortical electrical activity. In addition, the extent of the no-go alpha ERD reveals that refraining from performance of a pre-programmed movement is by no means a passive/inactive process.
Article
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.