Supriya Ray, Ph.D.
Vanderbilt University
Department of Psychology/Schall Lab

"To go or not to go: Where is the point of no return?"

The ability to timely initiate or inhibit planned actions is an important manifestation of control that allows efficient reactions to a dynamic environment. Inhibitory control is assumed to be exerted before the "point of no return" that defines a temporal boundary in response preparation beyond which a response is unstoppable. In the present study, a physiological signature of the "point of no return" of saccadic response has been identified using the countermanding task that requires inhibition of a gaze shift in response to the unpredictable appearance of a stop signal. Previously we have shown that if inhibitory control fails, saccade related neurons in frontal eye field (FEF) of a macaque monkey might start to correct their response before the error is visually realized (Journal of Neurophysiology, Murthy et al. 2007). Here I report that a subset of saccade related FEF neurons, namely visuomovement neurons, modulate to signal the occurrence of an error 25 ms before the production of the erroneous saccade. These neurons exhibited a moderately elevated discharge rate after the target onset and maintained this level for variable intervals until their activity either subsided when the monkey withheld a saccade or increased further when an imminent saccade could not be stopped. The time of modulation of visuomovement neurons is correlated not only with the reaction time of the erroneous saccade, but also with the fraction of trials that yielded erroneous saccades.

Department of Psychology NEUROSCIENCE SEMINAR SERIES

For additional information, contact Carol Wiley, carol.wiley@vanderbilt.edu