Neural Mechanisms Underlying Action with Mirror Visual Feedback

Mirror visual feedback (MVF) is a form of altered, illusory visual feedback that has shown promise in the treatment of stroke and chronic pain. This technique utilizes the visual feedback of a functioning limb to improve function in an impaired limb. Despite the growing interest in using MVF in rehabilitation, the mechanisms underlying this technique is unknown. Therefore, this thesis was undertaken to explore fundamental, yet unanswered, questions about the mechanisms underlying MVF of a precision grasp across three different studies. In Study 1, the excitability, intracortical inhibition and facilitation of the motor cortex (M1) ipsilateral to the moving hand in MVF was studied. Findings demonstrated increased excitability in the ipsilateral M1 and reduced short-interval intracortical inhibition only with MVF. Study 2 explored modulations in the connection between anterior intraparietal sulcus (aIPS), an area belonging to the mirror neuron system/precision grasping circuit, and M1 with MVF. Minimal involvement of the aIPS in MVF was noted. Changes in the ventral premotor cortex (PMv) and M1 connectivity with MVF was examined in Study 3. The PMv plays an important part in visually-guided precision grasping. This study found that the ipsilateral PMv-M1 interaction in the left hemisphere was inhibitory. Study findings highlight the role of the left PMv in MVF. Future studies should explore hemispheric differences in PMv-M1 in MVF. Together, this work demonstrates that the neural mechanism underlying MVF involve an increased excitation of the ipsilateral M1. MVF also influences the inhibitory intracortical circuits within M1. Although minimal evidence was found to suggest the involvement of aIPS in MVF, the role of the left PMv in MVF has been demonstrated. Most importantly, this thesis highlights different neural nodes that contribute to MVF and its impact on motor function.Ph.D