Spatiotemporal sensitivity of cortical responses to self- and object-related motion in human adults

Open Access
Author:
Fesi, Jeremy Daniel
Graduate Program:
Psychology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
April 20, 2012
Committee Members:
  • Rick Owen Gilmore, Dissertation Advisor
  • Rick Owen Gilmore, Committee Chair
  • Frank Gerard Hillary, Committee Member
  • Peter Cm Molenaar, Committee Member
Keywords:
  • vision
  • EEG
  • visual motion
  • electrophysiology
Abstract:
Motion provides animals with fast and robust cues for navigation and object detection. In the first case, stereotyped patterns of motion referred to as “optic flow” inform a moving observer about the direction and speed of its movement. In the case of object detection, regional differences of rigid motion allow for the segmentation of figures from their background, even in the absence of color or shading cues. Both classes of patterns are examples of complex motion, and are thus both dependent upon the integration of basic motion information across the visual field. Previous studies have attempted to chart visual evoked potential (VEP) response sensitivity to global space-time information in order to understand integrative versus local motion processing in the brain. However, important gaps remain, and so the experiments of this dissertation attempt to address these gaps. For instance, previous VEP studies on speed sensitivity concentrated only on one pattern type at a time, and only on optic flow. Experiments 1 and 3 therefore investigated the influence of pattern type on speed sensitivity for optic flow patterns and motion-defined figures, respectively. Experiments 2 and 4 provide human electrophysiological data for comparison with other studies on the temporal properties of motion integration mechanisms. Here, dot lifetimes were varied to determine the temporal constraints of the VEP responses to optic flow and motion-defined figures. Some of the results point to common mechanisms for the self- and object-motion patterns. Largely, however, the data suggest differential sensitivity: not only across the two classes of motion, but also across the patterns within each class, across scalp, and across speeds. Thus, the results demonstrate that normal cortical processing of integrative motion is much more complex than is often assumed.