Fig. 2: Endogenous dopamine transients predict average syllable use and sequence variability.
From: Spontaneous behaviour is structured by reinforcement without explicit reward
a, The unexpected food reward protocol. Top right, average spontaneous versus food reward-associated transients (Methods). Shading represents bootstrap s.e.m. Bottom right, probability density function of dLight transient amplitudes. The dotted line indicates the threshold for detecting dLight transient peaks. b, Left, robust linear regression between syllable-associated dLight and average syllable counts per syllable (each dot is a syllable–mouse pair). Regression line and kernel density estimate are shown (r is Pearson correlation between held-out predictions and actual data). Right, the distribution of Pearson correlations using models fit to shuffled data compared with the observed correlation (blue line). Shading indicates the 95% bootstrap confidence interval. P-values estimated by one-sided shuffle test. c, Schematic depicting the hypothesis that dopamine predicts changes in future behaviour. Blue star indicates the syllable-associated dopamine peak. d, Left, average dLight waveforms for each fluorescence quartile at syllable onset for an example syllable–experiment pair. Right, log2 fold change compared to average syllable counts after example syllable onset computed over increasing bin sizes (in syllables) after onset. e, The average Pearson correlation between syllable-associated dLight and syllable counts or velocity, and the dLight signal autocorrelation, computed using a set of increasing bin sizes after syllable onset. Grey shading represents the shuffled 95% confidence interval. The two x-axes reflect time in syllables and approximated in seconds. Solid bars indicate statistical significance (P < 0.05, one-sided shuffle test). f, The distributions of exponential decay timescales (τ) for the correlations plotted in Fig. 2e (n = 1,000 bootstrap samples). In all box plots in this Article, the horizontal line represents the median, box edges delineate the first and third quartiles, and whiskers include the furthest data point within 1.5 times the interquartile range of the first or third quartile. g, Average cross-correlation between binned syllable counts and syllable-associated dLight fluorescence (from all mice and experiments) across lags (P < 0.001, one-sided shuffle test; the arrow indicates average peak lag, error is 68% confidence interval). Grey shading represents the shuffled 95% confidence interval. h, Overall correlation between syllable-associated dLight and syllable usage for syllables temporally adjacent to the index syllable. Grey shading represents the shuffled 95% confidence interval. The solid bar denotes statistical significance (P < 0.05, one-sided shuffle test). i, As in b, but for average entropy per syllable. Nat, natural unit of information. j, As in d, but for sequence entropy for an example syllable–experiment pair. k, As in e, but for sequence entropy. l, Fitted τ values for the correlation curve in k (n = 1,000 bootstrap samples).
