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Sensorimotor integration: Basic concepts, abnormalities related to movement disorders and sensorimotor training-induced cortical reorganization
Abstract
Sensorimotor integration is defined as the capability of the central nervous system to integrate different sources of stimuli, and parallelly, to transform such inputs in motor actions.
To review the basic principles of sensorimotor integration, such as, its neural bases and its elementary mechanisms involved in specific goal-directed tasks performed by healthy subjects, and the abnormalities reported in the most common movement disorders, such as, Parkinson' disease, dystonia and stroke, like the cortical reorganization-related mechanisms.
Whether these disorders are associated with an abnormal peripheral sensory input or defective central processing is still unclear, but most of the data support a central mechanism. We found that the sensorimotor integration process plays a potential role in elementary mechanisms involved in specific goal-directed tasks performed by healthy subjects and in occurrence of abnormalities in most common movement disorders and, moreover, play a potential role on the acquisition of abilities that have as critical factor the coupling of different sensory data which will constitute the basis of elaboration of motor outputs consciously goal-directed.
... При цьому відбувається складна взаємодія висхідного потоку збуджень з керуючими імпульсами із мовленнєвих відділів кори головного мозку, які можуть вибірково посилювати або пригноблювати роботу окремих нервових структур, приймаючи на себе роль вищого акцептора результату дії і визначаючи складну динаміку психофізіологічного процесу як в його аферентній і центральній частині, так і в ділянці низхідних ефекторних систем [18]. ...
... Так, серед перших вірогідно переважають варіанти амбідекстрії (39,8%), в той час як у других в однаковій мірі найчастішими є варіанти праворукості (32,9%) та амбідекстрії (30%).З урахуванням розподілу за КА були сформовані 10 груп осіб окремо для чоловіків і жінок: з вираженою праворукістю -ВП Ч та ВП Ж , праворукістю -П Ч та П Ж , без переважання (амбідекстрів) -БП Ч та БП Ж , ліворукістю -Л Ч та Л Ж , вираженою ліворукістю -ВЛ Ч та ВЛ Ж , чисельний склад яких представлений у вищезгаданій таблиці.Для вирішення поставлених у роботі завдань нами досліджувались відмінності пересічних значень показників сенсомоторної функції, що досягалось з використанням непараметричних методів статистичного дослідження з визначенням критерію вірогідності відмінностей Ман-Уїтні.Як згадувалось вище показник ТЦР засвідчує провідність нейронних систем, включаючи синапси, що забезпечується низкою нейромедіаторів центральної нервової системи. В першу чергу, мова йде про провідні шляхи підкіркових утворень головного мозку, в яких відбувається перемикання нейронів різних відділів кори, мозочка, ядр екстрапірамідної системи тощо[18].групи ВП Ч у порівнянні з групою П Ч відзначаються при виконанні тесту лівою рукою (рис. 5а). ...
... Sensorimotor integration is a brain process that allows, through complex neural operations, the execution of certain voluntary motor behavior in response to specific demands of the environment. 1 Problematically, abnormalities in the peripheral afferent input or in the brain response to sensory input may interfere with the processing of motor programs in the cortical motor areas. 2 Effective sensorimotor integration is essential for learning new skills and for performing physical tasks. 3 Thus, athletic performance and the behavior pattern of normal and abnormal movement are intimately dependent on peripheral sensory feedback and sensory integration. ...
Objective:
To evaluate sensorimotor integration and skill-related physical fitness components for participants with forward head posture (FHP) compared with strictly matched controls with normal head alignment.
Material and methods:
We measured FHP, sensorimotor processing, and skill-related physical fitness variables in 50 participants with FHP and in 50 participants matched for age, gender, and body mass index with normal FHP, defined as having a craniovertebral angle >55°. Sensorimotor processing and integration variables were: (1) amplitudes of the spinal N13, (2) brainstem P14, (3) parietal N20 and P27, and (4) frontal N30 potentials. The skill-related physical fitness variables selected for the study were (1) T-test agility, (2) leg power, (3) stork static balance test, and (4) Y-balance test.
Results:
There was a statistically significant difference between the FHP group and control group for the sensorimotor integration variable: frontal N30 potentials (P < .05). Additionally, between-group differences were found for the sensorimotor processing variables: amplitudes of spinal N13, brainstem P14, and parietal N20, and P27 (P < .05). Statistically significant differences between groups for the skill-related physical fitness variables were also identified: T-test agility, leg power, stork static balance test, and Y-balance test (P < .05). The magnitude of the craniovertebral angle showed a correlation with all measured variables (P < .05).
Conclusion:
College athletes with FHP exhibited altered sensorimotor processing and integration measurements and less efficient skill-related physical fitness compared with athletes with normal sagittal head posture alignment.
... This information is then processed in light of a top-down organization where expectations and prior knowledge influence how the stimulus is perceived (1,2). In essence, sensorimotor integration is a process in which the central nervous system integrates different sources of information (sensory and prior information) and transforms them into motor actions (3). This processing allows humans to differentiate between internal (produced by our own movement) and external stimuli (4). ...
The pressure of our own finger on the arm feels differently than the same pressure exerted by an external agent: the latter involves just touch, whereas the former involves a combination of touch and predictive output from the internal model of the body. This internal model predicts the movement of our own finger and hence the intensity of the sensation of the finger press is decreased. A decrease in intensity of the self-produced stimulus is called sensory attenuation. It has been reported that, due to decreased proprioception with age and an increased reliance on the prediction of the internal model, sensory attenuation is increased in older adults. In this study, we used a force-matching paradigm to test if sensory attenuation is also present over the arm and if aging increases sensory attenuation. We demonstrated that, while both young and older adults overestimate a self-produced force, older adults overestimate it even more showing an increased sensory attenuation. In addition, we also found that both younger and older adults self-produce higher forces when activating the homologous muscles of the upper limb. While this is traditionally viewed as evidence for an increased reliance on internal model function in older adults because of decreased proprioception, proprioception appeared unimpaired in our older participants. This begs the question of whether an age-related decrease in proprioception is really responsible for the increased sensory attenuation observed in older people.
... Добре відомими є методи визначення властивостей ЦНС. Всі вони засновані на активних впливах на сферу умовно-рефлекторної діяльності або на зміну рівня мотивації, або на штучну зміну збудливості ЦНС при введенні медичних препаратів, або на зміну сили використовуваних подразників, черговості їх застосування, зміну їх просторово-часових характеристик, або на оцінці швидкості реакції на гальмівні і збуджуючі сигнали [8]. ...
The purpose of the study was a comparative analysis of sensorimotor reactions in highly trained athletes with different types of heart rate regulation.
Materials and methods. 202 highly trained male athletes aged 22.6±2.8 years, who are engaged in acyclic sports – martial arts (karate, taekwondo, kickboxing, boxing, freestyle wrestling, Greco-Roman wrestling, judo, sambo) and games (water polo, soccer) were examined. The experience in sports was 10.3±3.1 years. All studies were conducted in the pre-competition period in the morning.
Based on the study of heart rate variability in athletes, the type of heart rate regulation was determined. The basis for determining the types of regulation is the classification of heart rate variability indicators, taking into account their inclusion in certain limits. Heart rate variability indicators that reflect the dual-circuit model of heart rate regulation and are used for diagnosis include: total heart rate variability – total power (ms2), very low frequency (ms2), and stress-index (e.u.), which reflect the various chains of regulatory effects on heart rate.
According to certain data types, 4 groups were formed. 1 group (type I) consisted of 42 athletes, 2 (type II) – 28 athletes, 3 (type III) – 88 athletes, 4 (type IV) – 44 athletes. The study of sensorimotor function was performed using the device KMM-3.
Results and discussion. It is shown that the most balanced sensorimotor reactions are in athletes with type III regulation of heart rate. The most strain sensorimotor reactions are observed in type II regulation of heart rate, which is reflected in the pronounced central asymmetry of movement control with acceleration to the left against the background of deteriorating accuracy of right (due to flexors) and left (due to extensors) limbs, and the right-hand predominance. Sensorimotor reactions are quite strain in type IV of heart rate regulation, which is characterized by slow reactions at the synaptic and peripheral levels. In type I of heart rate regulation, the disorders observed at the central level of regulation relate to the asymmetry of short-term motor memory processes, which are significantly reduced in the left hemisphere.
Conclusion. The study shows that the differences in the regulatory support of heart rate in highly qualified athletes are accompanied by characteristic differences in sensorimotor function. The latter can be useful for the diagnosis and further correction of conditions associated with the development of overexertion and overtraining.
Keywords: types of autonomous regulation, heart rate, sensorimotor reactions, athletes.
... However, a few research probed RHI influence over sensorimotor integration and motor cortex excitability. The human motor system requires constant sensory input to execute the movements appropriately; this process was named sensorimotor integration (Machado et al., 2010). Therefore, sensory conflict during RHI may alter the sensorimotor integration so that corticomotor output could provide further information about the neural basis of RHI. ...
Objective
The Rubber Hand Illusion (RHI) manipulates body ownership experimentally and helps investigate the related neurophysiological processes. This study aimed to evaluate motor cortex excitability that hypothesized changed due to illusion.
Method
Twenty-one healthy (twelve male, nine female), right-handed volunteers aged between 25-50 years were recruited to the study. Short-Latency Afferent Inhibition (SAI) was evaluated by transcranial magnetic stimulation (TMS) given with a figure-of-eight-shaped coil from the left motor cortex, 21 ms after peripheral electrical stimulation. Short-Interval Intracortical Inhibition (SICI) and Intracortical Facilitation (ICF) were investigated using a paired-pulse TMS at interstimulus intervals (ISI) of 1, 2.5, 3 ms and 15, 20, 25 ms, respectively. We used custom-made illusion setups for TMS paradigms. SAI, SICI and ICF was evaluated before, during and 15 minutes after the RHI.
Results
Results of the study revealed significantly high SAI during illusion compared to pre-illusion, but no difference was found between post-illusion 15th minutes and control measurements. Significantly reduced SICI at 2.5 and 3 ms ISI obtained during illusion, while RHI did not affect SICI at 1 ms ISI and ICF.
Significance
Body ownership illusion modulates the motor cortex excitability, possibly through altered sensory processing and sensorimotor integration.
... However, these impairments can also result from direct tissue loss, as in the case of stroke Grefkes and Fink 2011;Carter et al. 2012;Adhikari et al. 2017) and traumatic brain injury (TBI) (Nakamura et al. 2009;Messé et al. 2013;Sharp et al. 2014;Caeyenberghs et al. 2017). Impairment from stroke, one of the most common causes of adult onset disability, stems from a combination of direct tissue loss and the disruption of sensorimotor integration leading to changes in motor performance (Machado et al. 2010). Rehabilitation from these sensorimotor deficits relies on reestablishing functional connectivity, including sensorimotor integration. ...
As our understanding of volitional motor function increases, it is clear that complex movements are the result of the interactions of multiple cortical regions rather than just the output properties of primary motor cortex. However, our understanding of the interactions among these regions is limited. In this study, we used the activity-dependent stimulation (ADS) technique to determine the short/long-term effects on network activity and neuroplasticity of intracortical connections. ADS uses the intrinsic neural activity of one region to trigger stimulations in a separate region of the brain and can manipulate neuronal connectivity in vivo. Our aim was to compare single-unit neuronal activity within premotor cortex (rostral forelimb area, [RFA] in rats) in response to ADS (triggered from RFA) and randomly-generated stimulation in the somatosensory area (S1) within single sessions and across 21 consecutive days of stimulation. We examined firing rate and correlation between spikes and stimuli in chronically-implanted healthy ambulatory rats during spontaneous and evoked activity. At the end of the treatment, we evaluated changes of synaptophysin expression. Our results demonstrated the ability of ADS to modulate RFA firing properties and to promote synaptogenesis in S1, strengthening the idea that this Hebbian-inspired protocol can be used to modulate cortical connectivity.
... In a neurologically normal participant, these systems act together to build a multisensory integration system for adjusting balance; as a result, when a sensory input from one of these systems decreases, the central integration resolves sensory conflict and selects an appropriate information from disparate sensory input to achieve the best result in controlling the balance 6) . Impaired somatosensory integration in stroke patients has been reported in several studies [7][8][9] . Several therapeutic strategies are designed to improve balance by manipulation of these three systems. ...
Objective:
Several strategies have been designed to improve balance after stroke. Although recent studies have suggested that the balance training in stroke should include exercises that are performed in different sensory conflict conditions, little attention has been paid to manipulation of visual input. This study aimed to compare effects of balance training on an unstable surface with balance training under visual deprivation conditions in persons with stroke.
Method:
Forty-five stroke patients were randomized into three groups: the visual deprivation- stable based training (VD-SBT); unstable based training (UBT); and control (C) groups. Subjects of the VD-SBT group performed balance training on a stable surface with closed eyes. The UBT group performed balance training on an unstable surface with open eyes. Patients were assessed before and after interventions for Timed Up and Go (TUG), Four Square Step (FSS) and Five Times Sit to Stand (FTSS) tests.
Result:
There was a significant difference in pre- post intervention time of TUG, FSS and FTSS tests in all three groups. In a comparison of three groups, the UBT and VD-SBT groups had a significant improvement in time of all tests but significant improvement in time of all tests was observed in the VD-SBT group in comparison with the UBT group. In the field of balance training, the manipulation of visual input was more effective than the manipulation of standing surface to reweighting the sensory information.
Conclusion:
We recommended balance rehabilitation programs after stroke performed under conditions to stimulate the use of underused sensory input.
... Further, differential alterations in functional connectivity between primary and supplementary motor cortex, and regions involved in brain motor circuitry such as putamen, thalamus, and cerebellum, have been suggested depending on the severity of the clinical presentation of atypical neurodevelopment [75]. Such evidence raises the question of a possible resulting impairment in the process of sensorimotor integration, that is the brain process allowing, by complex neural operations, the connection of the sensory and motor domains [76]. Deficiencies in sensorimotor integration would then present as difficulties in effectively utilizing sensory feedback to correct movements, resulting in the coordination difficulties and sensory reactivity abnormalities phenotypically observed among individuals with an NDD [77]. ...
Neurodevelopmental disorders (NDDs) have been suggested to lie on a gradient continuum, all resulting from common brain disturbances, but with different degrees of impairment severity. This case-control study aimed to assess postural stability against such hypothesis in 104 children/adolescents aged 5–17, of whom 81 had NDDs and 23 were healthy controls. Compared to healthy controls, Autism Spectrum Disorder (ASD) resulted in the most severely impaired neurodevelopmental condition, followed by Attention Deficit Hyperactive Disorder (ADHD) and Tourette Syndrome (TS). In particular, while ASD children/adolescents performed worse than healthy controls in a number of sensory conditions across all parameters, ADHD children/adolescents performed worse than healthy controls only in the sway area for the most complex sensory conditions, when their vision and somatosensory functions were both compromised, and performance in Tourette Syndrome (TS) was roughly indistinguishable from that of healthy controls. Finally, differences were also observed between clinical groups, with ASD children/adolescents, and to a much lesser extent ADHD children/adolescents, performing worse than TS children/adolescents, especially when sensory systems were not operationally accurate. Evidence from this study indicates that poor postural control may be a useful biomarker for risk assessment during neurodevelopment, in line with predictions from the gradient hypothesis.
... Sensory-motor integration is the body's ability to take in, organize/process, and respond in a meaningful and acceptable way to the sensory input. One of the many functions of the central nervous system is to combine multiple sources of environmental stimuli to translate these inputs into motor movements or processes involved in particular goal-directed tasks (Machado, Cunha, Velasques, Minc, Teixeira, Domingues et al., 2010). Such ability is what makes infants reach out to or grab at anything that they see hanging up their cribs or toddlers run after their favorite ball rolling across the room. ...
This multiple case study explored on the psychomotor and cognitive competencies of four Filipino children, ages one to four who came from different demographic background. This also determined other prominent psychomotor and cognitive competencies of these children not indicated in the NELC development standards (ECCD Council, 2015) and described relevant issues and concerns that impact their psychomotor and cognitive development using a researcher-developed early childhood development checklist and an interview guide for the children’s parents/guardians. The study was able to describe the psychomotor and cognitive competencies of four Filipino children based on the NELC development standards. There were specific psychomotor and cognitive competencies that were identified but not defined in the NELC standards, but they were recognized distinct to a child’s social context. Relevant environmental stimulations, especially, from primary caregivers were recognized as important determinants of children’s psychomotor and cognitive development. Furthermore, findings of the study conform to principles on child development and learning – that development proceeds at varying rates for each child and reflects children’s experiences and their environment. This implies that when planning programs and early learning experiences for children, individual and age appropriateness should be considered, and the child is understood as part of his/her environment. Further researches may explore other domains of development and other socio-cultural perspectives of development utilizing quantitative and qualitative research methodologies, which could involve bigger groups of children in different regions of the Philippines.
Background and Aims: Postural control disorder has been reported in Patellofemoral Pain Syndrome (PFPS) patients as the cause of pain, dysfunction in proprioception, and decreased muscle strength. The purpose of the present study was to investigate the effects of 12 weeks of sensorimotor training on pain, proprioception, strength, and postural control in PFPS patients. Methods: A semi-experimental study was carried out on 32 patients with PFPS who were randomly divided into experimental (n = 16) and control (n = 16) groups. The variables measured included pain, knee proprioception angles of 20 and 60 degrees, muscular strength quadriceps, hip abductor, and postural control, which were evaluated before and after intervention. We evaluated postural control using Biodex Device, pain with VAS scale, knee proprioception with goniometer, and muscle Strength via dynamometer. The experimental group performed sensorimotor Training for 12 weeks, 3 times per week) and 1 hour per session; however, the control group did not receive any treatment during this time. SPSS, version 21, was used for data analysis running covariance statistical method. Results: The results of data analysis showed that the experimental group had significant improvement in postural control index, Anterior-posterior index (P=0.002), medial-lateral Overall stability (P=0 .001), pain reduction (P=0 .001), knee proprioception of 20 degrees (P=0.001), knee proprioception of 60 degrees (P=0.001), muscle strength of quadriceps (P=0.002), and muscle strength of hip abductor (P=0.001) after 12 weeks of sensorimotor training. Conclusions: Sensorimotor training significantly reduced pain and improved knee proprioception, muscles strength, and postural control in PFPS patients; therefore, it seems that these training can be used as a comprehensive treatment protocol for the treatment of multiple disorders in patients with PFPS.
An old biological dogma states that a potencial for cortical reorganization (neuroplasticity) exists nly in young animals, being lost in adlt life. Here we review studies carried out both in animals and humans, whixh demonstrate cortical reorganization in sensory and motor systems in adult subjects. We particulary emphasiza human studies carried out with the aid of transcranial magnetic stimulation. The adult cortex is capable of reorganization after peripheral or central nervous system lesions and as a result of learning.
The role of vision was examined as infants prepared to grasp horizontally and vertically oriented rods. Hand orientation was measured prior to contact to determine if infants differentially oriented their hands relative to the object's orientation. Infants reached for rods under different lighting conditions. Three experiments are reported in which (1) sight of the hand was removed (N=12), (2) sight of the object was removed near the end of the reach (N=40, including 10 adults), and (3) sight of the object was removed prior to reach onset (N=9). Infants differentially oriented their hand to a similar extent regardless of lighting condition and similar to control conditions in which they could see the rod and hand throughout the reach. In preparation for reaching, infants may use the current sight of the object's orientation, or the memory of it, to orient the hand for grasping; sight of the hand had no effect on hand orientation.
The human brain is probably the most complicated single structure in the biological universe. The cerebral cortex that is traditionally connected with consciousness is extremely complex. The brain contains approximately 1,000,000 km of nerve fibers, indicating its enormous complexity and which makes it difficult for scientists to reveal the function of the brain. In this paper, we propose a new model for brain functions, i.e., information-guided self-organization of neural patterns, where information is provided from the abstract wholeness of the biophysical system of an organism (often called the true self, or the "soul"). We present a number of arguments in favor of this model that provide self-conscious control over the thought process or cognition. Our arguments arise from analyzing experimental data from different research fields: histology, anatomy, electroencephalography (EEG), cerebral blood flow, neuropsychology, evolutionary studies, and mathematics. We criticize the popular network theories as the consequence of a simplistic, mechanical interpretation of reality (philosophical materialism) applied to the brain. We demonstrate how viewing brain functions as information-guided self-organization of neural patterns can explain the structure of conscious mentation; we seem to have a dual hierarchical representation in the cerebral cortex: one for sensation-perception and one for will-action. The model explains many of our unique mental abilities to think, memorize, associate, discriminate, and make abstractions. The presented model of the conscious brain also seems to be able to explain the function of the simpler brains, such as those of insects and hydra.
Purpose: Electroencephalographic (EEG) recordings were examined at the temporal (T3, T4) regions of the cerebral cortex in novice pistol shooters (N = 11) over a training period of 12-14 wk to determine changes in activation. Mean alpha power and its rate of change were hypothesized to increase in the left temporal region during aiming from early to late season as participants improved their accuracy and reduced cognitive effort. Methods: Event-related alpha 11 power (ERAP; 11-13 Hz) was examined over a 5-s period preceding the trigger pull during shooting (SH) and two control conditions (resting baseline, BL; and postural simulation, PS) at early (time 1), middle (time 2), and late (time 3) practice. Results: Mean levels of ERAP increased at T3 from the beginning to the end of the training period during both SH and PS, but not BL, whereas no such change in mean level of ERAP was noted at T4 during any of the three conditions. The practice-related cortical adaptation during SH covaried with an increase in shooting percentage over the season. A higher rate of increase in ERAP during the 5-s aiming period of SH relative to that at PS and BL was also observed throughout training at both T3 and T4. Exploratory analysis of global power (sites F3, Fz, F4, C3, Cz, C4, P3, Pz, and P4) revealed that ERAP increased during SH from time 1 to time 3 at all sites except Fz and Pz, whereas only one site (C4) revealed an increase during BL. Conclusions: The reduction in cortical activity is likely due to sensorimotor integration and less cognitive effort due to automaticity.
Parkinson's disease is a neurological disorder that primarily affects older individuals and their ability to engage in daily occupations. Occupational therapists are actively involved in the training and retraining of functional motor skills with this population. Motor control theories may assist clinicians in understanding the movement difficulties that these individuals experience. Motor learning principles may be implemented to facilitate the learning of adaptive skills and/or previous motor tasks. Both motor control and motor learning research findings may influence occupational therapy treatment approaches for the rehabilitation of this population. The purpose of this paper is to review the current knowledge in the areas of motor control and motor learning, discuss this knowledge as it applies to Parkinson's disease, and integrate this information into occupational therapy treatment.
Parkinson's disease is a neurological disorder that primarily affects older individuals and their ability to engage in daily occupations. Occupational therapists are actively involved in the training and retraining of functional motor skills with this population. Motor control theories may assist clinicians in understanding the movement difficulties that these individuals experience. Motor learning principles may be implemented to facilitate the learning of adaptive skills and/or previous motor tasks. Both motor control and motor learning research findings may influence occupational therapy treatment approaches for the rehabilitation of this population. The purpose of this paper is to review the current knowledge in the areas of motor control and motor learning, discuss this knowledge as it applies to Parkinson's disease, and integrate this information into occupational therapy treatment.
Both Ghose and Maunsell and Shadlen and Movshon point out what is perhaps the fundamental problem with the binding hypothesis: even supposing that temporal coding is the vehicle for signaling which neural populations should be bound together, the theory does not adequately address how those combinations are computed. In a sense, the binding problem is pushed back one level, for it must be solved at least partially for the necessary temporal correlations to be established. Are neurons with appropriate receptive field properties and anatomical connectivity a sufficient basis for the generation of correlated signals? What is the role of top-down connections in establishing proper synchrony? These questions are difficult to answer and difficult to model with biological realism. A similar problem rests with the output side of the temporal binding hypothesis—if correlations are the signal for binding, how are those signals read out? The readout problem is one of the most puzzling and fundamental problems for systems neuroscience in general: how is the firing of populations of neurons interpreted and transformed by other neurons to result in decision, action, perception, etc? This problem plagues most, if not all, models of brain function, for in modeling it is the modeler that attributes semantics to nodes in a network. One way to potentially avoid that problem would be to close the loop between the model and the world, so that the world impinges upon the network, which then acts upon and affects the world, thus generating semantics through action.This brings me to mention (by virtue of my editorial license) what is perhaps the most mystifying binding problem of all: the problem of consciousness. How does something as simple and mechanistic as neural firing add up to subjectivity, raw feelings, a self? Are the mechanisms that allow us to attribute the correct color and shape to an object the same ones that lead to the unity of phenomenal experience? Will the solution of the binding problem be the solution to the mystery of consciousness? I will not belabor the point, since answers will be long in coming, but although none of the scientists who authored the reviews that follow discuss binding with respect to consciousness, I will wager that the a good part of the interest, excitement, and contentiousness that surrounds the binding debate is attributable to the magnitude of the issues with which it is connected. The following pieces provide a comprehensive review of the status of the binding problem at the dawn of the new millenium. It will be extremely interesting to repeat this exercise in a decade or two, to chart the progress that we as scientists make on one of the most puzzling and fascinating issues that the brain and cognitive sciences have ever faced.*E-mail: aroskies@cell.com.
Clinical observations of patients with writer's cramp suggest that abnormalities of the sensory system may be a frequent finding in this disorder. Neurophysiological data from an animal model of focal dystonia have revealed cells in somatosensory cortex with enlarged and overlapping tactile receptive fields. However, psychophysical studies so far have been unable to document a clinical correlate supporting a similar enlargement of receptive fields in humans. We compared the fingertip discrimination of the orientation of fine spatial gratings between writer's cramp and control subjects and found a significant decrease in grating sensitivity in the patients, consistent with the possibility of enlarged tactile receptive fields. In addition, we duplicated previous experiments showing an abnormality of tactile temporal discrimination. The results provide psychophysical measures which may relate to the development of sensory cortical reorganization in patients with writer's cramp. Mov. Disord. 16:94–99, 2001. © 2001 Movement Disorder Society.
Eye and head movements were measured in a group of infants at 2, 3, and 5 months of age as they were attentively tracking an object moving at 0.2 or 0.4 Hz in sinus or triangular mode. Smooth pursuit gain increased with age, especially until 3 months. At 2–3 months, the lag of the smooth pursuit was small for the sinusoidal motion but large for the triangular one. At 5 months, smooth pursuit was leading the sinusoidal motion and the lag for the triangular one was small. Head tracking increased substantially with age and its lag was always large.