Extended Data Fig. 7. Laser effect is more than a baseline shift.

a–d, Results from GABA stimulation experiment. e-h, Results from GABA inhibition experiment. a, Firing rate (mean ± s.e.m.) of putative dopamine neurons that did not show a significant baseline shift. ***, P < 0.001, t-test. b, To visualize whether GABA stimulation preferentially affected phasic dopamine responses in addition to baseline firing rates, we took the activity in Fig. 2c and subtracted the trials when laser was delivered alone. Any remaining change at the time of reward could not be due to a baseline shift. **, P = 0.01, t-test. c, Firing rate (mean ± s.e.m.) of putative dopamine (left) and GABA (right) neurons on trials where laser was delivered in the absence of reward. This dopamine response was subtracted to calculate the firing rates in b. d, Histogram of the phasic effect of GABA stimulation. The values were calculated by subtracting the black line from the blue line in b. Empty bars, slope not different from zero (P > 0.05, Wilcoxon rank-sum). Filled bars, slope different from zero (P < 0.05). Triangle, mean (P < 0.001, t-test). e-h, Same conventions as a–d, but for the GABA inhibition experiment. ***, P < 0.001, t-test.