Bimanual coordination and mirror visual feedback: implications for mirror therapy

Kim, Jin Min ORCID: 0000-0002-8571-8825 (2024). Bimanual coordination and mirror visual feedback: implications for mirror therapy. University of Birmingham. Ph.D.

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Abstract

Most movements in daily life are performed with both hands. Both hands may do the same movement at the same time, or they may play different roles in demonstrating bimanual coordination to achieve the task. Stroke patients show abnormal bimanual coordination due to motor impairment. Traditionally, strategies of practising unimanual tasks with the impaired limb of stroke patients have been adopted to improve motor impairment. However, training with both hands simultaneously has been proposed as a more effective training strategy. Simultaneous symmetrical movement of both hands can benefit from an interlimb coupling effect, in which the movement of one hand impacts the movement of the other. In other words, bimanual training for stroke patients may improve movement deficits in the affected limb and help restore bimanual coordination. A mirror has been suggested as a device that may enhance the effect of bilateral training.

During mirror therapy, a mirror is positioned perpendicularly between both hands by placing the affected limb behind the mirror. Patients are instructed to move the unseen affected limb as much as possible while watching the movement of the unaffected limb reflected in the mirror. This promising intervention improves motor impairment and motor function in hemiparetic stroke patients. However, procedures used in multiple clinical studies and in practice vary considerably, and the underlying mechanism(s) that underpin mirror therapy are not known. Since the main purpose of mirror therapy is to improve the motor function of the unseen affected hand, this thesis aimed to contribute to our understanding of mirror therapy by examining the movement of the unseen hand that occurs during mirror visual feedback.

This thesis reports experiments that carefully examined bimanual movements for both unimpaired individuals and hemiparetic stroke patients under mirror visual feedback conditions. In the initial experiments (Chapter 2), the marked positional drift of the unseen limb (the limb behind the mirror) was highlighted when unimpaired individuals made continuous bimanual circle-drawing movements with mirror visual feedback. It became apparent that one might be able to examine an individual’s ownership and agency over the illusory limb from moment to moment by identifying whether the movements of the unseen limb were modified in response to visual feedback created by the seen limb. A subsequent experiment and novel analytical approach in Chapter 3 addressed this issue. Chapter 4 applied the knowledge and techniques learned from the previous chapters in examining bimanual movements in a small number of stroke patients. Recent research suggests specific parameters (e.g., using a large mirror, not using objects) that may contribute to the optimal effectiveness of mirror therapy for stroke patients. In the final experimental chapter, the impact of modifying these parameters on the illusory limb as indicated by subjective ratings was explored in unimpaired participants. A comprehensive summary of the experiments and a general discussion of theoretical and clinical implications and future directions are presented in Chapter 6.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):