The majority of neurons (64.3%; 18/28) examined for the effects of PTV cooling were classified as complex cells: they had spatially overlapping on and off discharge regions to optimally oriented stationary flashing light bars and/or spatially overlapping discharge regions to moving optimally oriented bars darker and brighter than the background. Simple cells, characterized by spatially non-overlapping on and off discharge regions, and/or spatially non-overlapping discharge regions to moving optimally oriented bars darker and brighter than the background, constituted about a third (32.1%; 9/28) of the sample. We were unable to classify one cell (1/28; 3.5%) on the basis of the above criteria.