TitleAnticipatory smooth eye movements in response to global motion
NameSantos, Elio M. (author), Kowler, Eileen (chair), Papathomas, Thomas V (internal member), Torres, Elizabeth B (internal member), Rutgers University, Graduate School - New Brunswick,
Motion perception (Vision)
DescriptionAnticipatory smooth pursuit eye movements in the direction of expected target motion can be elicited by symbolic visual or auditory cues (Kowler, 1989). Stimuli in classical studies, small targets moving against dark or structured backgrounds, convey the perceptual impression of an object moving across space. Are such interpretations necessary for anticipatory pursuit? Random dot kinematograms (RDK's) can be pursued, and they generate global motion signals, rather than the percept of discrete moving objects. The present study used RDKs with brief lifetimes (52, 104, or 208 ms) to avoid the tracking of a single or subset of dots and to study the effects lifetime may have on pursuit velocities. The direction of motion was cued by either: (1) the spatial offset of the initial stationary fixation stimulus away from screen center, opposite to the direction of upcoming target motion; or (2) a tone whose frequency indicated whether dots moving downward would change direction to either down-right or down-left. Uncued motion directions, and unlimited lifetime dots, were also tested. Anticipatory smooth eye movements in response to cued global motion were seen about 100 ms before the onset of critical target motion. These results indicate that anticipatory smooth pursuit eye movements can be elicited with global motion, and limited lifetime elements, and do not require representations of an object moving across space. Neither anticipatory nor initial portions of pursuit depended on dot lifetime. When pursuit was initiated after fixation of a stationary pattern (Experiment 1), the effects of dot lifetime were seen by about 140 ms in the unpredictable condition and about 200 ms in the predictable condition. When there was a change in motion direction while pursuit was already underway, the effects of dot lifetime were noticeable earlier, by about 100 ms after the change in direction (Experiment 2). By contrast, eye velocity in later stages of pursuit varied with lifetime. These results show that it is possible to initiate anticipatory smooth eye movements in response to global motion, even without the representation of an object moving across space. The relatively long latency until effects of lifetime appeared suggest that the neural signals that control the anticipatory portions of pursuit may not be sensitive to the parameters of immediate target motion (Heinen, 1995).
NoteIncludes bibliographical references
Noteby Elio M. Santos
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.