DIRECTION BIASES OF X-TYPE AND Y-TYPE RETINAL GANGLION-CELLS IN THE CAT

1. It has been reported that in the cat only a specialized group of re tinal ganglion cells constituting similar to 1% of the overall populat ion are direction sensitive. Two major groups of retinal ganglion cell s, the X and Y cells, have been reported not to be sensitive to the di rection of stimulus motion. 2. We recorded action potentials of retina l ganglion cells intraocularly. We studied quantitatively the visual r esponses elicited by drifting sinusoidal gratings of various spatial f requencies, bars, and spots. 3. The results confirm previous reports t hat most cat retinal ganglion cells exhibit orientation biases when te sted with gratings of relatively high spatial frequency. 4. Additional ly, we find that 22% of X and 34% of Y type retinal ganglion cells exh ibit direction biases. Overall, Y cells displayed significantly strong er direction biases than did X cells. 5. In general, direction biases are dearest when the test gratings are of relatively low spatial frequ ency. 6. The direction biases of X and Y cells subserving the central 15 degrees of retina were weaker than those of cells subserving more p eripheral regions. 7. The direction-biased responses of cat ganglion c ells were similar to those of X and Y type relay cells in the cat dors al lateral geniculate nucleus (LGNd). Thus we suggest that the directi on biases of LGNd cells are a reflection of their retinal inputs.