96, P < 0.001). This suggests that ongoing LIP activity even before the stimulus array is presented was more likely to influence
the outcome of the behavioral trial. No significant difference was apparent during the stimulus presentation interval (t-test, t123 = 0.78, P > 0.4), although we saw a trend towards higher dlPFC values after ~150 ms, at the time interval when a significant difference between salient stimulus and distractors emerges in both areas. A higher choice probability in LIP neurons than in dlPFC neurons was also observed in the second 0.5 s of the delay period (t-test, t123 = −3.09, P < 0.01). The results indicate that higher firing rate of LIP neurons during the fixation and the delay period is more likely to result in correct performance of the task involving discrimination of a salient stimulus when it appears in the neuron's preferred location. BIRB 796 in vitro The analysis presented so far was performed with trials in which a salient stimulus appeared in neurons’ preferred location; these are characterized by a greater neural response to the salient
stimulus than to the distractors. Suppression of responses to non-target stimuli could also be an important factor in detecting the salient stimulus correctly. To further investigate how the response to distractors affects behavioral selleck screening library choice, we conducted an analysis of trials in which a distractor instead of the salient stimulus appeared in the neuron’s receptive field (Fig. 4). Megestrol Acetate A total of 73 neurons from dlPFC and 57 neurons from LIP were used in this analysis. In contrast to the trials with the salient stimulus in the receptive field, the firing rate of trials with the distractor in the receptive field (dlPFC, 1243 trials; LIP: 665 trials) tended to be higher in error than in correct trials (dlPFC, 1341 trials; LIP: 1108 trials); this was true for both areas (Fig. 4A
and B). Choice probability was now generally lower than 0.5; it was significantly different from 0.5 for both dlPFC and LIP during the cue (t-test; PFC, t72 = −4.89, P < 10−5; LIP, t56 = −4.63, P < 10−4) and delay period (t-test; PFC, t72 = −7.38, P < 10−9; LIP, t56 = −2.62, P < 0.05). A difference between dlPFC and LIP in the average choice probability was again present during the fixation (t-test, t128 = 2.04, P < 0.05) and the first 0.5 s of the delay period (t-test, t128 = −2.24, P < 0.05). Similar to the condition of the salient stimulus in the receptive field, LIP activity during the fixation period correlated more strongly with behavioral choice than the equivalent activity in dlPFC, though in this condition (when distractors appeared in the receptive field) elevated LIP activity during the fixation period was associated with a higher probability of an erroneous report. Elevated activity in dlPFC during the delay period affected the behavioral outcome more than did LIP activity, again being associated with an error when the distractor was in the receptive field.