Darian Cheng’s PhD Thesis Defence

Title:An examination of underlying motor planning and execution processes that are reflected in variations in cortical components during target encoding and execution of goal directed reaching movements”

Chair: Prof Kristen Campbell (Rehabilitation Sciences)
Supervisory Committee: Prof Romeo Chua (Kinesiology), Prof Gordon Binsted (Health and Exercise Sciences, UBC Okanagan), Prof Paul van Donkelaar (Health and Exercise Sciences, UBC
University Examiners: Prof Todd Handy (Psychology), Prof Tony Herdmann (Audiology and Speech Sciences)
External Examiner: Prof Jonathan Marotta, Department of Psychology, University of Manitoba

Abstract: In this thesis the electroencephalographic correlates associated with limb reaches under varying conditions of visual feedback, delay and movement difficulty were examined. The events of interest, wherein these correlates are observed were: 1) the encoding of a target (P3); and 2) the execution of a reaching movement towards the target (motor MP & N4). In study 1, the neural correlates associated with variations in task difficulty and target visible vs. target occluded were examined. The results of target encoding showed that P3 was greater when observed prior to reaches without than with vision of the target. Results of MP and N4 both varied based on task difficulty, as reaches to the far target yielded larger amplitudes than reaches to the close target. In study 2, the effects of visual feedback, delay condition, and presentation schedules (i.e., blocked vs. randomized) on target encoding and movement related cortical potentials was examined. For target encoding, component P3 failed to yield any significant differences across all vision, delay and presentation schedules. As for the movement related potentials, significant effects of delay were observed for component MP in the randomized protocol (i.e., larger MP in the long vs. the short delay), but not the blocked protocol. The analysis of N4 for the randomized protocol yielded a main effect of vision, as reaches with vision of the target attained greater negative amplitudes as compared with reaches without vision of the target. In the blocked protocol the analyses of N4 yielded a main effect of delay period as movements following long delay periods resulted in larger negative amplitudes. In study 3, the effects of real-time vision of the hand and target during a reaching movement on target encoding and movement execution were investigated. The findings revealed that the P3 component was modulated by the visibility of target. For the movement related cortical potentials, larger amplitudes for N4 were yielded for reaches without vision of the hand vs. reaches with vision of the hand. The three studies taken together provide insight into the neural events associated with goal-directed manual aiming under various reaching conditions.