When examining directional selectivity to the first cue light, the directional signal emerged earlier in gS trials (Fig. 4C, red; first 100-ms bin) compared to sS trials (Fig. 4C, orange; second 100-ms bin) and persisted longer in controls. This suggests that processing of the first cue light is diminished on sS trials in DMS, likely contributing to better performance on sS trials. Notably, this effect was not present in lesioned animals. Firing in DMS became directionally selective for both sS and gS within 100 ms after onset of the first light (Fig. 4F; t tests every 100 ms; P < 0.01). When comparing the two population histograms (Fig. 4 C and F), differences in the strength of the directional signal between control and lesion groups appear to rise from a reduction in firing to the presentation of the first cue light when it directed movement into the response field during sS trials (thin orange line) in controls. Indeed, when directly comparing the strength of this difference (i.e., gS – sS) during the first cue light epoch, we found that the
