The quantification of the online control of goal-directed movement using frequency domain analysis

The field of motor control has devoted a lot of attention to the use of sensory information during movements for the maintenance of accuracy. This sensorimotor processing has been colloquially termed online control. Its accurate quantification and identification has posed a continual challenge to motor control researchers. Consequently, many measures of online control have been developed and have shaped the concurrent state of the field. Recent theories of online control have posited the existence of multiple distinct feedback processes. The current dissertation sought to gain insights into the multi-faceted nature of online control by evaluating the utility of frequency domain analyses as a tool for its quantification. Frequency domain analyses were hypothesized to be sensitive to the aforementioned distinct feedback processes given the assumption that they operate at unique timescales. Four experiments were conducted and evidence was obtained in favour of the utility of frequency domain analyses for the quantification of online control. Specifically, frequency domain analyses were found to be both one of the most sensitive measures to online control and the most robust measure to offline contamination. Thus frequency domain analyses represent an excellent choice for the evaluation of online control processes. Additionally, theoretical insights were attained through the sensitivity of frequency domain analyses to the contribution of two distinct processes contributing to reaching performance. The first was an iterative visuomotor process that influenced reaching performance at relatively stable rates. Notably, the specific rate of influence was found to be flexible based on the spatio-temporal requirements of reaching movements. Additionally, frequency domain analyses were found to be sensitive to a second, non-visual process. This process was promoted in the absence of online vision and likely represented the contribution of a peripheral proprioceptive process. Importantly, contemporary alternative methodologies for the quantification of online control were not sensitive to the unique contributions of this secondary process. Altogether, the current dissertation reaffirmed and expanded upon the multi-faceted nature of online feedback utilization and provided a novel approach to its quantification.Ph.D