Characterization of sensory-motor behavior under cognitive load

This thesis introduces a new experimental paradigm and offers a unifying statistical framework to characterize possible interdependencies among signals of the nervous systems through three proposed fundamentally different types of processes. We have coined the terms deliberate, spontaneous and inevitable for these processes. Deliberate processes manifest through overt movements executed during goal-directed actions (e.g., when instructed to point to a visual target). They are systematic in nature, and are well characterized by low variability and robustness to changes in bodily physical dynamics. Spontaneous processes manifest through highly automatic and covert movements, that are uninstructed and goal-less (e.g., retracting the hand from a visual target), and are characterized by high variability and susceptibility to environmental cues and changes in bodily motion dynamics. These processes occur largely beneath the person’s awareness, but can be brought up to conscious control when instructed to do so. They co-exist with, and are incidental to the goal-directed segments of complex motions, as they provide fluidity to behavior at large. The inevitable processes are generated by autonomic activities such as the heartbeat. They have a narrower range of change in dynamics and cannot be volitionally controlled or be perturbed by environmental cues, unlike the deliberate and spontaneous processes. These processes are robust and provide a unique signature of the person’s nervous systems. Here, we study these processes in tandem as participants perform a basic pointing task with different levels of cognitive load in the context of decision making. We assess the continuous somatic-motor performance of the nervous system through a personalized statistical analysis of the moment-by-moment fluctuations in the amplitude and timing of various biophysical parameters. These include variations in the amplitude of the angular acceleration peaks and their inter-peak interval timing, and variation in the inter-heartbeat-interval timings (IBI). We find that the interdependency is funneled out through one of the processes depending on the demands of the task. Tasks with differing levels of cognitive load manifest the interdependency through inevitable processes with shifts in the IBI stochastic signatures. Decision-making (a form of cognitive load) manifests the interdependency through deliberate processes with fluctuations in the amplitude of the angular acceleration peaks, and through spontaneous processes with the inter-peak interval variations. We emphasize that these findings do not refer to discrete mouse-clicks or verbally reported data. They are rather in reference to continuous physiological data harnessed from the central, peripheral and autonomic nervous systems. As such, our methods are novel to the field of cognitive psychology. We discuss our results along with possible applications of this paradigm to basic science and clinical practices. Specifically, we invite their use in expanding the analytical tools for the nascent field of embodied cognition, and suggest these metrics to be used as dynamic outcome measures of voluntary, automatic, and autonomic control in clinical settings.M.S.Includes bibliographical referencesby Jihye Ry