Responses of visual single cells in the superior colliculus of the albino rat to bright bars.

We studied the responses of 57 visual cells of the superior colliculus of the albino rat to bright sweeping and stationary flashing bright bars to determine the properties of their receptive fields. We observed that 9% (8% in superficial and 11% in deep layers) of the studied cells presented orientation preference and 16% showed direction selectivity (13% in superficial and 22% in deep layers). According to their responses to a flashed bright bar they were classified in OFF-type (19%) and ON-OFF-type (81%). No ON-type cells were found. All cells were driven by the contralateral eye, and only in three cases was single cell activation from the ipsilateral eye possible. Twenty-one per cent (22% in superficial and 18% in deep layers) showed end-stopping when they were tested with bright bars of several lengths.