Upper Limb Asymmetries in the Utilization of Movement-related Sensory Feedback.

While the preferred arm of right handed individuals has traditionally been viewed as being dominant with respect to motor output, non-preferred arm advantages have recently been described by this laboratory for the matching of target arm positions in the absence of vision. The aim of this dissertation, therefore, was to determine the extent to which this asymmetry reflects arm differences in the utilization of movement-related feedback. To accomplish this, three matching experiments were conducted using servomotor-driven manipulanda devices that recorded elbow position in the horizontal plane. In study 1, a comparison was made between the static position matching abilities of the two arms during visually versus proprioceptively-guided tasks. In this case, non-preferred arm accuracy was found to be enhanced during the proprioceptive task, whereas the preferred arm made smaller errors when targets were visual in nature. In study 2, arm differences in the ability to match proprioceptively-determined target movement speeds were assessed. This study showed that, unlike the sense of arm position, the acuity of dynamic proprioception sense was relatively similar for the two arms, except in the case of average acceleration matching where a non-preferred arm accuracy advantage was seen. Lastly, in the third study, the ability to coordinate both arm position and movement speed proprioceptive information was tested. In this case, absolute matching errors were again smaller for the non-preferred versus preferred arm. Overall, the results of this dissertation lend support to the notion that the two arms rely to different degrees on visual versus proprioceptive feedback. This asymmetry may reflect the roles played by the two arms during the performance of many bimanual activities of daily living where vision guides movements of the preferred arm, while the non-preferred arm plays a more assistive role utilizing primarily proprioceptive feedback.Ph.D.KinesiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/57702/2/dgoble_1.pd

Mirror (a)symmetry? Visuo-proprioceptive interactions in individuals with spastic hemiparetic cerebral palsy

The work presented in this thesis aimed to get more insight into the previously reported positive effects of mirror visual feedback in children with spastic hemiparetic cerebral palsy (SHCP) and into visuo-proprioceptive interactions in children and adolescents with SHCP during goal-directed matching tasks. Individuals with SHCP have unilateral motor impairments that hamper them in accurate movement performance. In conjunction with the motor problems, these individuals experience sensory problems. The first study in this thesis (chapter two) found that mirror visual feedback of the impaired arm in SHCP led to significantly higher levels of neuromuscular activity than mirror visual feedback of the less-impaired arm. This indicates that the mirror-effect was not just caused by the illusory perception of symmetry between two limbs, and confirmed that the beneficial effect is dependent on mirror visual feedback of the less-impaired arm. In chapter three and four it was demonstrated that the ability of children with SCHP to match one (matching) hand with the position of the other (reference) hand, without visual information, is deteriorated when compared to typically developing children. However, if visual information of the static reference arm was available to the participants, the matching accuracy of the matching hand was significantly higher. Mirror visual feedback of the reference arm, generated by placing a mirror in between the arms in the sagittal plane, created the illusion that both hands were already at the endpoint. However, this did not impact upon the matching accuracy of the matching arm and resulted in similar error scores as regular feedback of the reference arm. Chapter five showed that moving the less-impaired arm in synchrony with the impaired arm resulted in higher matching accuracy than moving the impaired arm alone. Moreover, mirror visual feedback of the less-impaired arm improved matching accuracy for a subset of the participants. The effects of a short practice of a bimanual matching task with (mirror) visual feedback of the less-impaired arm on matching accuracy of the impaired arm was studied in chapter six. The results showed a higher matching accuracy of the impaired arm after the practice period. However, the role of the mirror is still inconclusive in this respect. From this it can be concluded that for individuals with SHCP practice of a matching movement can induce a transfer from visual to proprioceptive control of movement. Taken together, the work in this thesis showed that the deficit in position sense of the impaired arm in individuals with SHCP can be modified by visual feedback of the less-impaired arm. Although the role of mirror visual feedback is still inconclusive, it seems that motor learning can induce a transfer from visual to proprioceptive control of movement, which can have implications for therapy

Visual control of bimanual movements.

Goal directed reaching forms an integral part of human routine movements, and we have a remarkable faculty to perform such actions with both upper limbs and coordinating these to achieve individual and collective outcomes. Everyday actions such as eating using a knife and fork, tying shoelaces, typing on a keyboard distort the complexity involved in the nature of timing synchrony and coordination that occurs between the two limbs. Several factors that can affect the synchrony between limbs during concurrent bimanual movements are; task difficulty, required movement symmetry, competition between limbs for visual resources, hand dominance and impairment to motor or visual system. This thesis explores these factors through a series of experiments in both young and older unimpaired individuals as well as those with limb impairment as a result of stroke. Although observations in relation to movement of the upper limbs and their coordination have been recorded throughout written history, it is during the last few decades where the majority of related empirical research has been undertaken. How the brain controls and coordinates movement remains an important yet inconclusive area in motor control literature thus far, however, it grows as a topic of research due to more advanced technological capabilities and implications for upper limb movement disorder rehabilitation. Studies of the upper limb have considered the spatial and temporal properties of unimanual and bimanual movements; exploring the interaction between the two limbs during bimanual movements. In movements to two separate targets, movement time symmetry (temporal symmetry) has been observed between the two limbs, where the movements are initiated and terminated in similar timing. However, as the relative precision requirements and thus difficulty of the required movement to two separate targets increases, inter-limb coordination may be disrupted. To date, motor control research has failed to establish specific factors that are involved in the integration of the two limbs for bimanual coordination. As well as addressing the interaction between the two limbs, this thesis explores the contribution made by overt and covert visual attention to the control of visual guided upper limb movements with a focus on the coordination between the two limbs. It also explores related performance in stroke survivors with hemiparesis along with an older adults control group; in doing so, this research in the first to explore the important function of visually-guided bimanual movements while examining both eye and limb movements in a clinical population. This thesis is organised into three individual yet interconnected experimental chapters. Following introduction of the key themes motivating the research and related relevant literature (Chapter 1), a general methods section (Chapter 2) describes the development and details of the underlying experimental paradigm and protocol used in all the experimental chapters. Modifications to this basic approach are detailed in the methods sections of individual experimental chapters. Next, the experimental chapters are presented (Chapter 3, 4 and 5). Experiment 1 examines visual control and coordination of the limbs during unimanual and bimanual reaching movements in young left and righthanded adults (Chapter 3). Next, the experimental protocol was changed to restrict the visual control of upper limb movements and the motor coordination between the two limbs was studied (Chapter 4). Unimanual and bimanual movements were examined while participants maintained visual fixation (i.e. without eye movements), and any errant saccades were monitored in addition to the measures gathered in Chapter 3. The third experiment (Chapter 5) examined unimanual and bimanual control and coordination in participants following hemiparetic stroke and compared their performance with a group of age-matched control participants. A general discussion with conclusions and future directions is presented in Chapter 6

Mirror (a)symmetry?: Visuo-proprioceptive interactions in individuals with Spastic Hemiparetic Cerebral Palsy

Savelsbergh, G.J.P. [Promotor]Ledebt, A. [Copromotor]Deconinck, F.J.A. [Copromotor

Motor dysfunction in complex regional pain syndrome : the role of sensory processing and sensory-motor integration

In the chronic stage of Complex Regional Pain Syndrome (CRPS), motor disturbances are common and cause significant disability. The motor dysfunction of CRPS is a poorly understood phenomenon that is characterized predominantly by a decrease or loss of voluntary muscle control. This thesis aims to obtain a better understanding of the pathophysiology underpinning the motor dysfunction of CRPS by examining the potential roles of decreased inhibition of the motor system, changes in sensory processing and problems in sensory-motor integration. In specific, characteristics of muscle activity recordings are scrutinized in order to determine whether the loss of voluntary motor control and abnormal postures in CRPS exhibit characteristics of dystonia that are associated with reduced inhibition of the motor system (i.e., excessive muscle activation and enhanced mirror activity). The potential role of impaired processing of proprioceptive information related to wrist orientation and force production is examined, as well as the involuntary and voluntary (sensory-)motor interactions between the affected and unaffected arm. Furthermore, a systematic review of the literature on the motor consequences of experimental pain in healthy humans is presented in order to gain insight into the potential role of pain-related processes in the motor and sensory and motor disturbances of CRPS.This PhD project was performed within TREND (Trauma Related Neuronal Dysfunction), a Dutch Consortium that integrated research on epidemiology, assessment technology, pharmacotherapeutics, biomarkers and genetics on Complex Regional Pain Syndrome type 1. TREND was supported by an unrestricted grant from the Dutch Ministry of Economic Affairs (BSIK03016). Financial support for this thesis has kindly been provided by the Patiëntenvereniging Complex Regionaal Pijn Syndroom.UBL - phd migration 201

In Search of Manual Asymmetries in Aging during Performance of Activities of Daily Living: Does Upper Limb Performance Become More Symmetric with Age?

Introduction: A common disorder arising most frequently after a left hemisphere stroke is limb apraxia. Limb apraxia is a deficit of skilled movement, such as performance of activities of daily living (ADLs), that is not a result of primary motor or sensory impairments, or deficits in motivation, memory, or comprehension (De Renzi, 1990). Currently, clinical neuropsychological assessment of apraxia relies largely on qualitative analyses of gross movements during the performance of activities of daily living in two task conditions (pantomime and tool). Further, apraxic patients often perform ADLs with their non-dominant limb to avoid often-present right-hand hemiparesis, but the assessment does not adequately account for this. Thus, it is unclear whether movement deficits are due to non-dominant limb use or limb apraxia. Moreover, it is not known how different task conditions and aging influence the performance of ADLs in healthy populations, as well as manual asymmetries. Purpose: The purpose of this thesis was to: 1. determine if age affects the magnitude of manual asymmetry in the performance of two ADLs (drinking water from a cup and slicing a loaf of bread with a knife); 2. determine if different task demands (pantomime and tool condition) affect magnitude of manual asymmetries during the performance of ADLs; and 3. determine if aging affects how task demands are expressed during the performance of ADLs. Methods: Fifty healthy right-hand dominant (as determined via Waterloo Handedness Questionnaire) younger and older adults participated in this study. A grooved pegboard task was completed by all participants prior to performance of the two ADLs using motion tracking. Upper limb movements (dominant and non-dominant limb) were captured at 60 Hz via a motion capture system (Vicon, Oxford, UK). Participants performed two task conditions: 1) pantomime (pretending to perform an ADL without holding the tool); and 2) tool (pretending to perform an ADL while holding the tool) in two ADLs: drinking water from a cup and slicing a loaf of bread with a knife. Each ADL was performed six times by both limbs. ADLs and limbs were randomized, while task conditions were blocked randomized between participants. Results: Overall, this study found that aging slows down motor performance on the Grooved Pegboard task, as well as the performance of both ADLs. Manual asymmetries were task dependent. The cup and knife ADL were both characterized by larger manual asymmetries in older adults relative to the younger adult group, particularly in terms of angular movement. Further, it was found that task demands were expressed differently in older adults relative to younger adults, with the tool condition yielding performance improvements in both groups. Conclusions: Despite the previous research, which has shown that manual asymmetries are reduced in older adults during the performance of motor tasks, this investigation points to the opposite during the performance of activities of daily living. Aging appears to increase the degree to which manual asymmetries are expressed. Further, aging also appears to play a role in the change in temporal and angular aspects of movement during the performance of ADLs in different task conditions. The degree to which task demands as reflected in the two task conditions improve or impair performance in healthy populations should be taken into consideration when evaluating ADL performance in patients with limb apraxia. In accordance with the previous research on aging, this study has shown that upper limb movements become slower as individuals age. Kinematic relationships presented in this study provide researchers and clinicians with an insight into how manual asymmetries, aging and different task demands come into play during the performance of one cyclical and non-cyclical task

On sensorimotor function and the relationship between proprioception and motor learning

Research continues to explore the mechanisms that mediate successful motor control. Behaviourally-relevant modulation of muscle commands is dependent on sensory signals. Proprioception -- the sense of body position -- is one signal likely to be crucial for motor learning. The present thesis explores the relationship between human proprioception and motor learning. First we investigated changes to sensory function during the adaptation of arm movements to novel forces. Subjects adapted movements in the presence of directional loads over the course of learning. Psychophysical estimates of perceived hand position showed that motor learning resulted in sensed hand position becoming \emph{biased} in the direction of the experienced load. This biasing of perception occurred for four different perturbation directions and remained even after washout movements. Therefore, motor learning can result in systematic changes to proprioceptive function. In a second experiment we investigated proprioceptive changes after subjects learned highly accurate movements to targets. Subjects demonstrated improved acuity of the hand\u27s position following this type of motor learning. Interestingly, improved acuity did not generalize to the entire workspace but was instead restricted to local positions within the region of the workspace where motor learning occurred. These results provide evidence that altered sensory function from motor learning may also include sensory acuity improvements. Subsequently the duration of acuity improvements was assessed. Improved acuity of hand position was observed immediately after motor learning and 24h later, but was not reliably different from baseline at 1h or 4h. Persistent sensory change may thus be similar to retention of motor learning and may involve a sleep-dependent component. In the fourth study we investigated the ability of proprioceptive training to improve motor learning. Subjects had to match the position and speed of desired trajectories. At regular intervals during motor motor learning, subjects were presented with the desired trajectory either only visually, or with both vision and and passive proprioceptive movement through the desired trajectory using a robot. Subjects who received proprioceptive guidance indeed performed better in matching both velocity and position of desired movements, suggesting a role for passive proprioceptive training in improving motor learning