Spatial summation of signals and adaptation by the surround response mechanism of cat retinal ganglion cells.

The summing properties of the surround response mechanism of cat retinal ganglion cells were assessed by determining area-sensitivty and area-adaptation curves. The two curves were found to be similar for X and Y cells but for many Y cells adaptive sensitivity was found to be dependent upon the size of the test target. These results suggest that, for X cells, the retinal area over which the surround integrates signals and adaptation are spatially coextensive. Most Y cells appear to pool adaptive effects over a smaller region than they pool signals.