Fig. 5.

Responses to movement in the nondiscriminating zone of a directionally selective retinal ganglion cell. The responses of the cell to edges moving behind an aperture were tested. The aperture was located in one of these zones, on the null side, the preferred side, or the center of the receptive field. The stimulus was a light rectangle 500 × 500 μm moving at 200 μm/sec behind a 100 × 200 μm aperture. ON responses refer to the leading edge of the moving stimulus, OFF responses to the trailing edge. The moving edges were aligned parallel to the longer axis of the aperture. The zones illustrated in the micrograph are 100-μm-wide but extend further vertically than the aperture tested, to allow better visualization of dendritic detail in the three tested zones. After recording had been completed, the cell was injected with Lucifer yellow. When the aperture was positioned on the preferred side of the receptive field, the difference in response between preferred and null directions was much less than elsewhere in the receptive field. Histograms show mean responses for 10 trials.