Fig. 3: Correlation of identified SNc DAN activity with reward rate.

a Selective expression of ChRWR/Venus in SNc DANs. Schematic diagram of the vector injection site (AAV2-EF1α-Flex-ChRWR/Venus) in the left SNc, and the stimulation site via the optical fiber in DMS and DLS for optogenetic spike collision test (top-right). Left panels show Venus expression in the left striatum (top), left midbrain (middle), and SNc neurons (bottom). Center panels show tyrosine hydroxylase (TH) staining in the striatum (top), midbrain (middle), and SNc neurons (bottom). Right middle and bottom panels show overlapping of Venus and TH expression in the SNc neurons. b Identification of striatum projecting DANs by spike collision test. Representative spike activity in one tetrode around optical stimulation. Black traces represent antidromic spikes evoked by optical stimulation (cyan). Yellow traces show the absence of the antidromic spike after optical stimulation triggered by spontaneous spikes, confirming a successful spike collision. The spike waveforms are shown in red. c Response of DMS- and DLS-projecting DANs aligned with movement onset and outcome (rewarded or non-rewarded) tones. The yellow horizontal line represents a significant difference (p < 0.01, bin = 20 ms; t-test) between rewarded (red) and non-rewarded (blue) responses. Horizontal black bars indicate outcome tone duration. d Reward rate correlation of SNc-DMS with Go cue period activity during rewarded (red) and non-rewarded (blue) trials. All error bars represent SEM. On each box, the central dot indicates the median, the bottom and top edges of the box indicate the 25th and 75th percentiles, respectively. The whiskers show the extreme data points not considered outliers. The histograms show r value distribution of individual neurons; colored bars represent significant correlation. The central mark on the box plot indicates the median, the bottom and top edges of the box indicate the 25th and 75th percentiles, respectively. The whiskers show the extreme data points not considered outliers; p value indicates the comparison between the distribution of r values and 0 (Wilcoxon rank-sum test). e Same as d for movement onset period. f Same as d for outcome period. g Reward rate correlation of SNc-DLS during Go cue period. h Same as g for movement onset period. i Same as g for outcome period. j Comparison of the strength of the neural activity correlation with reward rate between SNc-DMS and SNc-DLS. Difference of z-score of the correlation coefficients using Fisher’s z-transformation. Each dot represents one neuron. The error bars correspond to the confidence interval; *p < 0.05, **p < 0.01; α = 0.05. Fisher’s z-test.