SPATIOTEMPORAL RECEPTIVE-FIELD STRUCTURE OF PHASIC W-CELLS IN THE CATRETINA

The spatio-temporal receptive-field structure of 54 phasic W cells in cat retinas has been examined using the reverse-correlation method of Jones and Palmer (1987). Within this sample, 12 cells had on-center, 1 6 off-center, and 26 on-off receptive fields. Three of the on-center a nd seven of the on-off cells were directionally selective. Forty perce nt of the cells in this sample had local receptive fields consisting o f two or more distinct subregions. However, no correlation was observe d between the number of subregions in the local receptive field and ot her response properties such as center sign or direction selectivity. In all cases, individual subregions, including those in on-off cells, appear to be produced by a half-wave rectification of the input signal . For 76% of the cells, these local receptive fields were contained wi thin large suppressive fields which could be seen to extend for at lea st 10 deg in all directions with no apparent spatial structure. The me chanism producing the suppressive field also appears to involve a rect ification of the input signal, and has a relatively high spatial resol ution. Furthermore, the suppressive field itself is only responsive to moving or flickering stimuli; large, stationary gratings have no effe ct on the output of the local receptive-field mechanism. Thus, the ove rall receptive-field organization of these cells is particularly well suited for detecting local motion. The remaining 24% of cells in the s ample lacked suppressive fields, and consequently responded well to la rge moving stimuli, but these cells were otherwise similar in their re ceptive-field properties to eels with suppressive fields. The signific ance of these properties is discussed in the context of the projection s of phasic W cells to the superior colliculus and accessory optic sys tem.