Figure 5.

Influence of D1 antagonist on saccadic latency. (A) Trial-by-trial changes in the latency of contralateral saccades, before (black) and after (red) injection of a D1 antagonist into the CD. Data are from Nakamura and Hikosaka (2006, p. 60). (B) Simulated trial-by-trial changes in saccade latency. (C) After D1 antagonist injection, average saccade latency increased in big-reward trials, but not in small-reward trials. The experimental data was replicated by computer simulation. (D) Hypothesized mechanism of the effect of D1 antagonist in big-reward trials. The D1 antagonist effectively elevates the D1 threshold and therefore induces a smaller-than-usual LTP in the direct pathway MSNs, whereas the indirect pathway MSNs are unaffected. The attenuated LTP leads to a weaker activation of the SC and therefore a longer latency saccade. (E) Hypothesized mechanism of the effect of D1 antagonist in big-reward trials. The DA level remains below the D1 threshold similarly to the control condition (Figure 2D) and therefore the saccade latency is not changed.