Responses of neurons in primary visual cortex are modulated by eye position

1. We tested the effects of eye position on the visual excitability of 88 neurons in the primary visual cortex of awake cats trained in oculomotor tasks. For most cells, we examined responses evoked by retinotopically identical stimuli for centered gaze, 8 degrees to the left of center, and 8 degrees to the right of center. 2. An effect of eye position was observed for 40% of the cells. For 13%, responsiveness varied by a factor of 2 or more. Most commonly, response was maximal with gaze shifted to one side, minimal when shifted to the opposite side, and intermediate for centered fixation. The exceptions were four cells for which excitability varied symmetrically with fixations to either side of center. 3. Variability in excitability associated with eye position is a wide-spread phenomenon, having been observed in the lateral geniculate nucleus, V1, and extrastriate cortex. These results are consistent with the belief that such variability is utilized in constructing a head-centered frame of reference from a retinotopic input.