Figure 8.

Coding of response-outcome (R-O) association. (A) The proportion of neurons coding actions (responses: R) (i), rewards (outcomes: O) (ii) and R-O associations (iii). In regression analysis with variable-reward-condition trials, the proportion of neurons with significant regression coefficients is shown: p < 0.01 in a two-sided Student's t-test. Orange and green lines indicate neurons in the prelimbic cortex and dorsomedial striatum, respectively. When the proportion of neurons exceeded the threshold (32.3%), we defined that the prelimbic cortex or the striatum significantly represented the variable (z-test, p < 0.05). In each column, proportions of neurons are aligned with a different timing: left, initiation of center-hole poking; middle, end of center-hole poking; right, onset of reward or no-reward cue (R/NR cue). Gray bars in the middle column show the timing of right- or left-hole poking in 99.3% of all trials. Small black triangles indicate that the proportions of neurons in the prelimbic cortex and dorsomedial striatum had significant differences: p < 0.01 in a χ²-test. (B) Representative prelimbic cortical neuron encoding the R-O association. Neural activities at the onset of reward or no-reward cues in the variable-reward condition are shown, as in the right column of (A). Green and orange colors show left and right choices in rewarded trials, respectively. Light blue and red colors show non-rewarded trials. Raster plot: colors of spikes differ with actions and outcomes of trials. Tone presentations and poking periods are shown with gray boxes. The lower part shows the average spike density function smoothed with a Gaussian kernel with a standard deviation of 50 ms.