Visual control of bimanual movements.

Sardar, Shilokh David (2021). Visual control of bimanual movements. University of Birmingham. Ph.D.

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Abstract

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.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):