Figure 2.

Responses of LIP neurons on the 4-choice task are consistent with bounded accumulation. Firing rates are aligned to key events in the course of a trial, which are marked by vertical lines. For the trials depicted here, motion was either random (0% coherence) or in the T_in direction, (a) Average firing rates from 1 neuron. Left: responses aligned to onset of the choice targets; middle: responses aligned to the onset of stimulus motion; right: responses aligned to saccade initiation. For saccade-aligned responses, only T_in choices are shown. For purposes of display, traces are smoothed with a 30 ms exponential filter, (b) Responses reflect termination of the decision. Responses are grouped by RT at the values indicated (± 25 ms). The averages are aligned to saccade initiation and exclude neural activity within 200 ms of motion onset. Only correct T_in choices are included, and for clarity, every other RT group is not displayed. (c,d) Population average responses (N=70 neurons). Same conventions as in (a) and (b), except that no smoothing was performed; firing rates were computed in 20 ms non-overlapping bins. Arrow in (c) indicates the dip in firing rate seen shortly after motion onset. Arrow in (d) indicates the time when responses appear to coalesce, approximately 60 ms before the saccade.