Figure 4.

Single spikes can encode motion of high SF targets with certainty. A, For a V1 complex DS cell, seven STAs are shown for values of SF ranging from low (thin solid lines) to medium (dashed lines) to high (thick solid lines). From low to high SF, the STAs form a progression from a smoothed triangular shape (open arrow) to a flat-topped form (filled arrow) that indicates 100% certainty (1 on the vertical axis) that motion was in the preferred direction 35-55 msec preceding a spike. The negative lobe of the STA also extends downward, signaling an antipreferred motion with 86-93% probability from 61 to 73 msec before a spike. Thus, for the high SF stimulus, a very particular and precisely timed pattern of motion (almost always a motion reversal) was required to make this cell fire. B, Similar behavior is shown for STAs for an example MT cell. The STA for the highest SF tested (filled arrow) reaches its asymptote of 1 from 50 to 62 msec before a spike.