Moreover, we find activity related to signed reward prediction Gemcitabine purchase errors, the teaching signal of the reinforcement learning model, in the ventral striatum and the same part of the ACC where learning-related changes were observed. These results provide strong evidence for perceptual learning-related changes in higher order brain regions. Furthermore, these results suggest that perceptual as well as reward learning and decision-making can be understood in the framework of reinforcement learning and that both forms of learning are based on a common neurobiological mechanism. During the course of 4 days 20 subjects (11 male, mean age ±

SEM, 26.3 ± 0.74) participated in an orientation discrimination task involving explicit performance feedback (Figure 1A). In each trial subjects Selleckchem CH5424802 saw a low contrast Gabor in the right upper visual field for 500 ms while fixating on a central fixation cross. The orientation of the Gabor could deviate from 45° in both directions (counterclockwise and clockwise). Subjects were asked to indicate the perceived orientation (tilted toward counterclockwise versus tilted toward clockwise) on a response mapping screen. After the response, the fixation cross turned green given a correct decision

or red given an erroneous response. Days 1 and 4 each involved six runs (110 trials each) of training while BOLD signals were acquired by using fMRI (Figure 1B). Days 2 and 3 each involved 15 behavioral training runs in a mock scanner. Performance on the task (percentage of correct decisions) increased with training, demonstrating a robust effect of perceptual learning (Figure 1C). A one-way ANOVA with repeated measures on percentage correct revealed a significant main effect of run substrate level phosphorylation (F(41,779) = 6.49, p < 0.001). Furthermore, a more parsimonious one-way ANOVA comparing performance between training days revealed a significant effect of day (F(3,57) = 20.70, p < 0.001) with significant differences between all days (p < 0.05, Bonferroni corrected, Figure 1C, right). Learning

involved a steepening of the psychophysical function relating the stimulus to the perceptual decision (Figure 1D), i.e., subjects became increasingly sensitive to small deviations from 45°. To quantify this improvement in orientation discrimination, we fitted a sigmoidal function to the psychophysical data of each subject and each day (Figure 1D, right). A one-way ANOVA with repeated measures on the slopes of this function revealed a significant main effect of day (F(3,57) = 31.97, p < 0.001). Post hoc t test confirmed that the slope increased with every training day (p < 0.05, Bonferroni corrected). Taken together, these results provide strong evidence for improvements in perceptual decision-making over the course of learning.