Space-Time Domain Maps

Receptive field plots obtained from 40ms flashes of bright and dark bars. These responses are from 4s test trials that were preceded by 8s of either blank screen or a 4Hz drifting grating. The dark map is subtracted from the bright map to derive the difference map. Red areas show bright-excitatory and blue areas show dark-excitatory regions.

Each of these maps is derived from a total of approximately 1000s of sparse noise stimulation. Responses were computed via a reverse-correlation procedure.

Figure 8

Difference between control and adapted maps

Figure 9 is simply the subtraction of the adapted from the control map. Note that the aftereffects have the same spatiotemporal orientation as the cell. One might suppose that this map is simply a scaled version of the control map, as would happen if adapting simply reduced response amplitude. However, close inspection will reveal that this map is shifted in both space and time relative to the cell's receptive field. Adapting alters spatiotemporal receptive field structure, and one can explain specific aftereffects on this basis.

Figure 9

Impulse response functions

Responses at 0.4 deg, where the timing aftereffect was seen with the sinusoidally-modulated bars (fig. 7). Note that adapting alters timing, but the aftereffect seen with sinusoidal stimuli can't be derived from these impulse response functions, since convolving them with sine waves will yield sine waves with identical changes in onset and offset.

Figure 10

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