Figure 1.

Spatiotemporal receptive fields for different classes of simple striate cortex cells. Shown are the cells’ temporal impulse responses, from 30 to 180 msec after stimulus onset, along the width dimensions of the RFs. Excitatory responses to light increments are shown in red, and excitatory responses to decrements in blue. (A) Spatio-temporal RF of a typical strongly biphasic simple cell. This cell responded to white bars in the RF center and black bars on the flanks, with the response reversing later. (Right) A time cross-section through the RF center (dotted line). This cell started responding at about 50 msec after stimulus onset; the response reached its peak at 70 msec and then reversed phase at 81 msec, with the second phase reaching its peak at 110 msec. (B) Spatio-temporal RF of a typical weakly biphasic simple cell. Note in the time cross-section (Right) that the initial response is considerably slower, with a peak at 106 msec, and that there is little if any reversed phase. (C) Spatio-temporal RF for a typical directionally selective simple cell. Note the leftward tilt in space-time of the RF subregions of this cell, which responded to patterns moving in one direction but not the other. (Right) The RF’s first and second SVD components. Note that the latency of the early component (open symbols) corresponds closely to that of the strongly biphasic nondirectional cell shown in A, and the latency of the later component (closed symbols) corresponds closely to that of the weakly biphasic cell shown in B.