Hand Coordination Research Articles

Characteristics of Unintentional Movements by a Multijoint Effector

ABSTRACTThe authors explored the phenomenon of unintentional changes in the equilibrium state of a multijoint effector produced by transient changes in the external force. The subjects performed a position-holding task against a constant force produced by a robot and were instructed not to intervene voluntarily with movements produced by changes in the robot force. The robot produced a smooth force increase leading to a hand movement, followed by a dwell time. Then, the force dropped to its initial value leading to hand movement toward the initial position, but the hand stopped short of the initial position. The undershoot magnitude increased linearly with the peak hand displacement and exponentially with dwell time (time constant of about 1 s). For long dwell times, the hand stopped at about half the total distance to the initial position. The authors interpret the results as consequences of a drift of the referent hand coordinate. Our results provide support for back-coupling between the referent and actual body configurations during multijoint actions and produce the first quantitative analysis of this phenomenon. This mechanism can also explain the phenomena of slacking and force drop after turning visual feedback off during accurate force production task.

Improvement in Paretic Arm Reach-to-Grasp following Low Frequency Repetitive Transcranial Magnetic Stimulation Depends on Object Size: A Pilot Study.

Introduction. Low frequency repetitive transcranial magnetic stimulation (LF-rTMS) delivered to the nonlesioned hemisphere has been shown to improve limited function of the paretic upper extremity (UE) following stroke. The outcome measures have largely included clinical assessments with little investigation on changes in kinematics and coordination. To date, there is no study investigating how the effects of LF-rTMS are modulated by the sizes of an object to be grasped. Objective. To investigate the effect of LF-rTMS on kinematics and coordination of the paretic hand reach-to-grasp (RTG) for two object sizes in chronic stroke. Methods. Nine participants received two TMS conditions: real rTMS and sham rTMS conditions. Before and after the rTMS conditions, cortico-motor excitability (CE) of the nonlesioned hemisphere, RTG kinematics, and coordination was evaluated. Object sizes were 1.2 and 7.2 cm in diameter. Results. Compared to sham rTMS, real rTMS significantly reduced CE of the non-lesioned M1. While rTMS had no effect on RTG action for the larger object, real rTMS significantly improved movement time, aperture opening, and RTG coordination for the smaller object. Conclusions. LF-rTMS improves RTG action for only the smaller object in chronic stroke. The findings suggest a dissociation between effects of rTMS on M1 and task difficulty for this complex skill.

Deficits of hand coordination and laterality of carotid endarterectomy.

Neurocognitive performance is used to assess multiple cognitive domains, including motor coordination, before and after carotid endarterectomy (CEA). Although gross motor strength is impaired with ischemia of large cortical areas or of the internal capsule, the authors hypothesize that patients undergoing CEA demonstrate significant motor deficits of hand coordination contralateral to the operative side, which is more clearly manifest in the nondominant hand than in the dominant hand with ischemia of smaller cortical areas. The neurocognitive performance of 374 patients was evaluated with a battery of neuropsychometric tests. Both asymptomatic and symptomatic patients undergoing CEA were included. The authors evaluated the patients' dominant and nondominant hand performance on the Grooved Pegboard test, a test of hand coordination, to demonstrate their functional laterality. Neurocognitive dysfunction was evaluated as the difference in performance before and after CEA according to group-rate and event-rate analyses. The z scores were generated for all tests using a reference group of patients who were having simple spine surgery. Dominant and nondominant motor coordination functions were evaluated as raw scores and as calculated z scores. According to event-rate analysis, significantly more patients undergoing CEA of the opposite carotid artery demonstrated nondominant than dominant hand deficits of coordination (41.2% vs 26.4%, respectively, p = 0.02). Similarly, according to group-rate analysis, in patients undergoing CEA of the opposite carotid artery, raw difference scores from the Grooved Pegboard test reflected greater nondominant than dominant hand deficits of coordination (21.0 ± 54.4 vs 9.7 ± 37.0, respectively, p = 0.02). Patients undergoing CEA of the opposite carotid artery are more likely to demonstrate nondominant than dominant hand deficits of coordination because of greater dexterity in the dominant hand before surgery.

The effect of mirror therapy on upper-extremity function and activities of daily living in stroke patients.

The purpose of this study was to examine the effects of mirror therapy on upper-extremity function and activities of daily living in chronic stroke patients. [Subjects and Methods] Fifteen subjects were each assigned to a mirror therapy group and a sham therapy group. The Fugl-Meyer Motor Function Assessment and the Box and Block Test were performed to compare paretic upper-extremity function and hand coordination abilities. The functional independence measurement was conducted to compare abilities to perform activities of daily living. [Results] Paretic upper-extremity function and hand coordination abilities were significantly different between the mirror therapy and sham therapy groups. Intervention in the mirror therapy group was more effective than in the sham therapy group for improving the ability to perform activities of daily living. Self-care showed statistically significant differences between the two groups. [Conclusion] Mirror therapy is effective in improving paretic upper-extremity function and activities of daily living in chronic stroke patients.

Improving accessibility of mobile devices with EasyWrite

This paper describes the development process of EasyWrite, a text-entry method for mobile devices that allows people with hand coordination problems to use small computer devices such as smartphones, tablet PCs, or other touchscreen machines. This text-entry method aims at improving typing accuracy and reducing frustration of people affected by this motor disability when using small devices. EasyWrite was developed following an iterative and user-centred process. Starting from requirements elicited from observing potential users with mild and moderate motor disabilities and information provided by a literature review, a low-fidelity prototype was built and evaluated. This early prototype was refined throughout several design and evaluation iterations. Its current state is a functional prototype that works on Android phones. The functional prototype usability was evaluated through user tests. The result of this process is a small virtual keyboard for mobile devices that has less and bigger keys as compared to other onscreen keyboards. The concept of EasyWrite is largely based on the notion of scanning group systems, but it allows users to navigate directly through groups and subgroups of characters by tapping on directional keys in order to find the desired character rather than waiting for a visual cursor to advance through the options, one at a time, at a specific time rate. Though at its current stage the method proposed by EasyWrite shows some limitations, it appears to be appropriate for users with moderate motor disabilities. For this group of people, user test results indicate that EasyWrite could be a more adequate text-entry method than the one provided by standard keyboards, both physical and onscreen, commonly found in mobile devices.

Differential motor alterations in children with three types of attention deficit hyperactivity disorder.

To determine frequency of motor alterations in children with attention deficit hyperactivity disorder (ADHD). We evaluated 19 children aged 7-12 years with ADHD classified in three sub-types: Combined (ADHD-C), with Inattention (ADHD-I), and with Hyperactivity (ADHD-H). Controls were age- and gender matched healthy children. We utilized Bruininks-Oseretsky Test of Motor Proficiency (BOTMP) for measuring motor skills. We observed differences between children with ADHD and controls in BOTMP general score and in static coordination, dynamic general- and hand- coordination, and in synkinetic movements. We also found differences in dynamic hand coordination between controls and children with ADHD-C; in dynamic general coordination between controls and children with ADHD-H; and in frequency of synkinetic movements between controls and children with ADHD-H. Children with ADHD with a major degree of hyperactivity showed greater frequency of motor alterations.

Neuromodulation and cognitive rehabilitation: addressing the methodological issue of circadian rhythms.

Most organisms, including humans,exhibit daily rhythms in their biological activities, physiological functions, and homeostatic mechanisms such as cell regeneration, hormone production, cardiac output, blood pressure, blood flow distribution, and body temperature. The physiological system responsible for these rhythms is known as the circadian system. Circadian changes have increasingly become an interesting focus of research, concerning also neurobehavioral functioning of healthy subjects. The impact of factors such as the sleep–wakefulness cycle and biological time-of-day on measures of subjective alertness has been extensively studied (1, 2). Moreover, there is compelling evidence of circadian dependency also for cognitive functions such as attention, memory, and learning (3, 4). Recently, it has been consolidated in different experimental models, including mammalian brain, that the circadian clock has a role in regulating structural synaptic plasticity, opening the new relevant concern of circadian-dependent neural plasticity (5,6). Interestingly, it has been suggested that changes in the electrical properties of the cell membrane (intrinsic plasticity) and in the release of neuromodulatory molecules due to the internal clock can reconfigure circuit dynamics leading individual neurons to switch among different functional networks throughout the day (5). Daily rhythmicity in neural activity has been further elucidated by Blautzik et al. (7) who analyzed the daily course of connectivity patterns. The authors found different degrees of daily modulation across connectivity patterns, ranging from networks characterized by stable activity across the day and networks with highly rhythmic connectivity changes. Based on the reported findings, we can infer that the aforementioned oscillatory processes in connectivity strength and spatial extent would eventually determine highly individual fluctuations of effective connectivity over the course of the day. Circadian rhythms show also to exert influence on the excitability of the cerebral cortex, as found by Lang et al. (8). In this study, the excitability of the primary motor cortex (M1) of healthy subjects was evaluated by transcranial magnetic stimulation (TMS) at different times of the day. Data unveiled that both the intracortical and the corticospinal excitability of M1 exhibited a progressive decrease during the course of the day. In the last years, it has emerged that the effectiveness and reproducibility of several techniques able to induce neuroplastic changes in humans, such as paired associative stimulation (PAS), are influenced by time-of-day of the intervention (9) and subjected to circadian modulation. As demonstrated by Sale et al. (10), who tested 25 subjects twice, at 8:00 a.m. and 8:00 p.m., on separate days, PAS effectiveness is enhanced in the evening,when endogenous cortisol is low; conversely, effects of PAS in the evening are blocked by a single oral dose of hydrocortisone. Additionally, in a large study of humans aged 50–70 years, high salivary levels of cortisol appeared to be related with poor performances on a wide range of cognitive domains, including language, verbal learning, processing speed, memory, and eye–hand coordination (11). Overall, the circadian modulation of several neural properties and structures, at both the microscopic and functional levels, may deeply affect cognitive behavior, responsiveness, and performance within the day. Despite its potential impact, timeof-day is rarely contemplated when brain responses and cognitive functions are studied. As a matter of fact, in order to minimize possible biases related to circadian effects, some neurophysiological studies are conducted with evaluations and/or interventions performed at the same time of the day. Still, these experimental designs do not contemplate another relevant factor, which may strongly affect the reliability of the collected data that is the interindividual variability of the biological clock. This physiological variability of circadian rhythms between subjects has led to the notion of individual chronotypes (12, 13). The chronotype influences the organization of physiological functions, behaviors, and cognitive performances throughout the day (1, 14, 15). Given the differences in circadian rhythmicity between chronotypes, specific individual variations in task performance are likely to occur as a function of time-of-day. In other words, this implies that the scheduled task may not be necessarily synchronized to the most optimal moment in the day for each tested participant (16, 17). The regulation of the endogenous dynamics that characterizes a chronotype is dictated by many factors. The thorough understanding of these mechanisms is critical to gain a comprehensive view on their functional implications and, further, may be considerably useful when addressing the experimental limitations due to diurnal rhythmicity. Among them, cortisol is a main neuromodulator that mediates circadian processes. The normal diurnal pattern of cortisol secretion has been

Acute hemicerebellitis in a young adult: A case report and literature review

Acute hemicerebellitis, marked by headache with or without cerebellar signs, is a rare clinical entity involving a unilateral cerebellar hemisphere. The pathogenesis of acute hemicerebellitis remains unclear, and the disease rarely occurs in adults. Here, we report an 18-year-old woman who presented with a lack of coordination of the right hand and leg lasting longer than one week, following a pulsatile headache. A neurological examination disclosed ocular dysmetria, right-sided limb ataxia and slight truncal ataxia. Cerebrospinal fluid analysis showed mononuclear pleocytosis. The serology and autoimmune studies were unremarkable. Brain magnetic resonance imaging (MRI) revealed a focal signal change in the right cerebellar hemisphere and vermis. Acute hemicerebellitis was diagnosed, and the patient was treated with intravenous methylprednisolone sodium succinate and acyclovir. Subsequently, the headache resolved, and the cerebellar signs were markedly improved. Twenty days after admission, she became asymptomatic and brain MRI showed resolution of cerebellar hyperintensity on the right side. In conclusion, we identified only 6 additional patients with adult-onset acute hemicerebellitis from previous reports, highlighting the importance of recognizing this rare clinical entity. Its clinical outcome is usually favorable, but in the acute phase, attention should be directed toward clinical symptoms that are suggestive of increased intracranial pressure.

Effect on badminton players by selected exercises of flexibility and co-ordination

The aim of the investigator to find out the effect of selected exercises on flexibility and co-ordination of Badminton players. Badminton has an important place in the world of sports. It has grown enormously in popularity over the last few years. Exercise is very important for the development of co-ordination and flexibility of Badminton players. For that purpose twenty badminton players of Degree College of Physical Education, Amravati were selected as the subjects. The age of the subject was ranging in between 18 to 25 years. Random group design was adopted for the study. The subjects were equally divided into two groups. i.e. experimental and control group. Each group was considered of 10 subjects. The experimental group went through a training programme of selected exercises for a period of six week. The control group engaged with their regular physical activity only. The data was collected before and immediate after completion of 6 weeks training programme by using the Sit and Reach Test Shoulder Elevation Test, Eye Hand Coordination test and Eye Foot Coordination Tool. To find out the significant difference of mean performance of control group and experimental group-t test was applied. To test the hypothesis the level of significance was set at 0.05 level of confidence. The findings of this study revealed that there is a significant improved in the performance of the experimental group after six week training programme but there is no significant improvement to the performance of the control group.

P037: Characteristics of the Abbreviated Mental Test Score (AMTS) and Montreal Cognitive Assessment (MoCA) in consecutive older acute medicine patients

movements, on a touch screen while their eye movements were monitored using an eye tracking system. Based on performance parameters as describing timing and execution of eye and hand movements, patients were divided into a ‘fast’ and a ‘slow’ group. Measures of ADL and IADL interference, assessed using standardized scales, were compared between groups. Results: Dementia patients in the ‘slow’ group reported more frequently IADL interference in the categories reaching destinations beyond walking distance, shopping, meal preparing and work around the house. No differences between groups were found in frequencies of reported ADL interference. Conclusions: The results indicate that impairments found in a planning based eye–hand coordination task may be related to the degree of (I)ADL interference in dementia patients. This might suggest a prognostic role of eye–hand coordination in predicting future disability in dementia patients.

P032: Eye–hand coordination: a new behavioral biomarker for early-stage Alzheimer's disease

P032: Eye–hand coordination: a new behavioral biomarker for early-stage Alzheimer's disease

P036: Impaired eye–hand coordination as a novel biomarker of disability in dementia: a pilot study

P036: Impaired eye–hand coordination as a novel biomarker of disability in dementia: a pilot study

Unintentional movements produced by back-coupling between the actual and referent body configurations: violations of equifinality in multi-joint positional tasks.

We tested several predictions of a recent theory that combines the ideas of control with referent configurations, hierarchical control, and the uncontrolled manifold (UCM) hypothesis. In particular, we tested a hypothesis that unintentional changes in hand coordinate can happen following a long-lasting transient perturbation. The subjects grasped a handle with the right hand, occupied an initial position against a bias force produced by the HapticMaster robot, and then tried not to react to changes in the robot-produced force. Changes in the force were smooth and transient; they always ended with the same force as the bias force. The force-change amplitude and the time the force was kept at the new level (dwell time) varied across conditions. After the transient force change was over, the handle rested in a position that differed significantly from the initial position. The amplitude of this unintentional movement increased with the amplitude of transient force change and with the dwell time. In the new position, the across-trials joint configuration variance was mostly confined to a subspace compatible with the average handle coordinate and orientation (the UCMs for these variables). We view these results as the first experimental support for the hypothesis on back-coupling between the referent and actual body configurations during multi-joint actions. The results suggest that even under the instruction "not to react to transient force changes," the subjects may be unable to prevent unintentional drift of the referent configuration. The structure of joint configuration variance after such movements was similar to that in earlier reports on joint configuration variance after intentional movements. We conclude that the intentional and unintentional movements are products of a single neural system that can lead to intentional and unintentional shifts of the referent body configuration.

Task-specific stability in muscle activation space during unintentional movements.

We used robot-generated perturbations applied during position-holding tasks to explore stability of induced unintentional movements in a multidimensional space of muscle activations. Healthy subjects held the handle of a robot against a constant bias force and were instructed not to interfere with hand movements produced by changes in the external force. Transient force changes were applied leading to handle displacement away from the initial position and then back toward the initial position. Intertrial variance in the space of muscle modes (eigenvectors in the muscle activations space) was quantified within two subspaces, corresponding to unchanged handle coordinate and to changes in the handle coordinate. Most variance was confined to the former subspace in each of the three phases of movement, the initial steady state, the intermediate position, and the final steady state. The same result was found when the changes in muscle activation were analyzed between the initial and final steady states. Changes in the dwell time between the perturbation force application and removal led to different final hand locations undershooting the initial position. The magnitude of the undershot scaled with the dwell time, while the structure of variance in the muscle activation space did not depend on the dwell time. We conclude that stability of the hand coordinate is ensured during both intentional and unintentional actions via similar mechanisms. Relative equifinality in the external space after transient perturbations may be associated with varying states in the redundant space of muscle activations. The results fit a hierarchical scheme for the control of voluntary movements with referent configurations and redundant mapping between the levels of the hierarchy.

Video Processing to Locate the Tooltip Position in Surgical Eye–Hand Coordination Tasks

Trajectories of surgical instruments in laparoscopic surgery contain rich information about surgeons' performance. In a simulation environment, instrument trajectories can be taken by motion sensors attached to the instruments. This method is not accepted by surgeons working in the operating room due to safety concerns. In this study, a novel approach of acquiring instrument trajectories from surgical videos is reported. A total of 12 surgical videos were obtained for this study. The videos were captured during simulated laparoscopic procedures where subjects were required to pick up and transport an object over 3 different targets using a laparoscopic grasper. An algorithm was developed to allow the computer to identify the tip of the grasper on each frame of video, and then compute the trajectories of grasper movement. The newly developed algorithm successfully identified tool trajectories from all 12 surgical videos. To validate the accuracy of this algorithm, the location of the tooltip in these videos were also manually labeled. The rate of accurate matching between these 2 methods was 98.4% of all video frames. Identifying tool movement from surgical videos creates an effective way to track instrument trajectories. This builds up the foundation for assessing psychomotor performance of surgeons in the operating room without jeopardizing patient safety.

Both age and physical activity level impact on eye-hand coordination

Aging impacts on our ability to perform goal-directed aiming movements. Older adults generally make slower and shorter initial impulses towards the end target, and therefore require more time for corrections in the final movement stage. Recent studies however suggest that a physically active lifestyle may attenuate these age-related changes. Also, it remains unclear whether eye-movement control exhibits a similar pattern of adaptation in older adults. Therefore, the first aim of this study was to describe how age and physical activity level impact eye–hand coordination during discrete manual aiming. Young and older participants were divided into physically active and sedentary subgroups, and performed discrete aiming movements while hand and eye movements were recorded. Secondly, to determine whether older adults depend more on vision during aiming, the task was repeated without visual feedback. The results revealed that the typical age-related hand movement adaptations were not only observed in older, but also in sedentary young participants. Older and sedentary young participants also spent more hand movement time after the eyes fixated the end target. This finding does not necessarily reflect an augmented reliance on vision, as all groups showed similar aiming errors when visual feedback was removed. In conclusion, both age and physical activity level clearly impacted eye–hand coordination during discrete manual aiming. This adapted coordination pattern seems to be caused by other factors than an increased reliance on vision.

Lags in measuring eye-hand coordination.

We challenge a number of the claims for novelty and innovation made in a recent published paper (Lee et al., 2014) with regard to a computerised methodology that these authors present for assessing eye-hand coordination (EHC). Published work on similar pre-existing computerised systems is discussed and arguments made for these alternative systems being equal, if not superior, in terms of their innovativeness. The commentary does not dispute the usefulness of systems such as the one described by Lee et al. Rather, in the interests of scholarship it provides an accompanying insight into the significant scholarly contributions previously, and contemporaneously, being made by other research groups working in this area.

Eye–hand coordination in on-line visuomotor adjustments

When we perform a visually guided reaching action, the brain coordinates our hand and eye movements. Eye-hand coordination has been examined widely, but it remains unclear whether the hand and eye motor systems are coordinated during on-line visuomotor adjustments induced by a target jump during a reaching movement. As such quick motor responses are required when we interact with dynamic environments, eye and hand movements could be coordinated even during on-line motor control. Here, we examine the relationship between online hand adjustment and saccadic eye movement. In contrast to the well-known temporal order of eye and hand initiations where the hand follows the eyes, we found that on-line hand adjustment was initiated before the saccade onset. Despite this order reversal, a correlation between hand and saccade latencies was observed, suggesting that the hand motor system is not independent of eye control even when the hand response was induced before the saccade. Moreover, the latency of the hand adjustment with saccadic eye movement was significantly shorter than that with eye fixation. This hand latency modulation cannot be ascribed to any changes of visual or oculomotor reafferent information as the saccade was not yet initiated when the hand adjustment started. Taken together, the hand motor system would receive preparation signals rather than reafference signals of saccadic eye movements to provide quick manual adjustments of the goal-directed eye-hand movements.

Scaling and coordination deficits during dynamic object manipulation in Parkinson's disease

The ability to reach for and dynamically manipulate objects in a dexterous fashion requires scaling and coordination of arm, hand, and fingertip forces during reach and grasp components of this behavior. The neural substrates underlying dynamic object manipulation are not well understood. Insight into the role of basal ganglia-thalamocortical circuits in object manipulation can come from the study of patients with Parkinson's disease (PD). We hypothesized that scaling and coordination aspects of motor control are differentially affected by this disorder. We asked 20 PD patients and 23 age-matched control subjects to reach for, grasp, and lift virtual objects along prescribed paths. The movements were subdivided into two types, intensive (scaling) and coordinative, by detecting their underlying self-similarity. PD patients off medication were significantly impaired relative to control subjects for both aspects of movement. Intensive deficits, reduced peak speed and aperture, were seen during the reach. Coordinative deficits were observed during the reach, namely, the relative position along the trajectory at which peak speed and aperture were achieved, and during the lift, when objects tilted with respect to the gravitational axis. These results suggest that basal ganglia-thalamocortical circuits may play an important role in fine motor coordination. Dopaminergic therapy significantly improved intensive but not coordinative aspects of movements. These findings are consistent with a framework in which tonic levels of dopamine in the dorsal striatum encode the energetic cost of a movement, thereby improving intensive or scaling aspects of movement. However, repletion of brain dopamine levels does not restore finely coordinated movement.

Juggling revisited — A voxel–based morphometry study with expert jugglers

Juggling is a highly interesting tool to investigate neuroplasticity associated with motor-learning. Several brain-imaging studies have reported changes in regional brain morphology in visual association cortices in individuals learning how to juggle a three-ball cascade. However, to our knowledge there are no studies that investigated expert jugglers, looking for specific features in regional brain morphology related to this highly specialized skill.Using T1-weighted images and voxel-based morphometry we investigated in a cross-sectional study design 16 expert jugglers, able to juggle at least five balls and an age- and gender-matched group of non-jugglers. We hypothesized that expert jugglers would show higher gray matter density in regions involved in visual motion perception and eye-hand coordination. Images were pre-processed and analyzed using SPM8. Age was included in the analyses as covariate of no interest.As compared to controls jugglers displayed several clusters of higher, regional gray matter density in the occipital and parietal lobes including the secondary visual cortex, the hMT+/V5 area bilaterally and the intraparietal sulcus bilaterally. Within the jugglers group we also found a correlation between performance and regional gray matter density in the right hMT+/V5 area.Our study provides evidence that expert jugglers show increased gray matter density in brain regions involved in visual motion perception and eye–hand coordination, i.e. brain areas that have previously been shown to undergo dynamic changes in terms of gray matter increases in subjects learning a basic three-ball cascade. The extent to which transient increases in beginners and the differences in experts and non-experts are based on the same neurobiological correlates remains to be fully elucidated.