Figure 5.

Using Optogenetic Phasic Dopamine Stimulation to Train Mice in the Task

(A) Schematic coronal section of the mouse brain (at the bregma, 3.1 mm) showing ventral tegmental area (VTA) and fiber optics implanted above VTA to elicit release of dopamine (DA).

(B) Confocal images showing expression of ChR2-EYFP (green) in TH⁺ (DA) neurons (red) and overlay showing both (yellow). The bars quantify the specificity of expression, showing statistics of ChR2-EYFP and TH⁺ expression in midbrain neurons (n = 1,460 neurons counted in 121 confocal images acquired from 11 mice).

(C) Stability of ChR2 expression in DAergic neurons (n = 11 mice).

(D) Rapid learning of the task in 3 mice receiving DA stimulation as a reward. Red and orange lines show rapid increase in the performance of naive mice that were solely trained with optogenetic DA stimulation. Blue curves show results for mice that trained with water reward (median and quartile ranges, replotted from Figure 1).

(E) Same as in (D), as a function of training day.

(F) Psychometric function obtained from example animal (orange line in C and D) on the 12^th day of behavioral training. Error bars show 95% binomial confidence intervals.

(G) Mean trials per day of mice receiving DA stimulation (red) compared to water reward (blue). Error bars represent SEM (smaller than the dot for water reward).