Is saccade adaptation guided by reinforcement?

City College Of New York, New York NY

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Abstract

Description (provided by applicant): When one chooses to look at something, one makes a saccadic eye movement to it. Because saccades are so brief, they cannot be guided by visual feedback, but must rely on feedback after each saccade to check the accuracy of that movement and, if needed, to adjust subsequent saccades;this is saccade adaptation. Although the specific mechanisms underlying saccadic adaptation are largely unknown, it is generally inferred that saccades are recalibrated depending on the retinal error after each saccade, i.e., the distance of the fovea from the target of the saccade. In the laboratory, saccade adaptation is induced by consistently and surreptitiously moving the target during each saccade (when vision is poor), with the result that the oculomotor system compensates as though its saccades had been in error. We propose to explore whether saccade adaptation is best described in engineering terms as a servo mechanism that reduces an error signal, or in behaviorist terms as an example of motor learning driven by reinforcement. We propose to compare two forms of saccade adaptation: (a) that produced conventionally by moving the target during the saccade, and (b) that produced by rewarding subjects for making saccades of a particular magnitude without the target being present after the saccade. Specifically we propose to see if the two forms of adaptation are interchangeable, and to train subjects to associate an arbitrary auditory signal with retinal error. Because one makes a saccade to see a target better, we propose to reward subjects for saccades of certain sizes by changing their view of the target after each saccade. We anticipate that this will reveal what aspects of the visual signals are important to the saccade adaptation mechanism. We hope that understanding the relationship of learning to saccade function will open the door to using saccades to study learning disorders and to using learning disorders to study saccades. PUBLIC HEALTH RELEVANCE Changes in saccadic eye movements are indicators for a variety of neurological and psychiatric disorders, including and Alzheimer's Disease;deficiencies in the ability to make adaptive changes in saccadic eye movements have been described in Parkinson's Disease. In this application, we propose that reinforcement, a general learning mechanism, may guide saccade adaptation. If confirmed, it may provide a rationale for investigating whether deficiencies in saccade adaptation may be useful in diagnosing learning disorders or dyslexia.