Fig. 3.

Optical stimulation of ChR2 expressing dopamine neurons leads to neuronal and behavioral correlates of value. a Top, monkeys viewed visual stimuli that predicted liquid reward delivered with (blue) or without (red) accompanying optical stimulation. a Bottom, larger neuronal response (blue) occurred to cues that predicted optical stimulation, compared to neuronal responses (red) to cues that did not predict optical stimulation. Blue raster plot and PSTH aligned onto the appearance of cues predicting reward plus optical stimulation. Red raster plot and PSTH aligned onto the appearance of cues predicting reward alone in the same neuron. b Monkeys made saccade guided choices between two visual cues (same reward scheme as in a). When the optical fiber was placed in the channelrhodopsin-infected hemisphere, monkeys learned to choose the cue that predicted optical stimulation, over the cue that did not predict optical stimulation (blue, ‘injected’). When the optical fiber was placed in the contralateral hemisphere, where no channelrhodopsin virus was injected, the monkeys continued to choose either option with equal frequency (red, ‘control). Thus, the monkeys’ choices indicated that optical stimulation added value. Two choice sessions are shown, one with the optical fiber in the infected hemisphere (blue) and one session with the optical fiber in the control, uninfected hemisphere (red). The ‘x’ indicates trial-by-trial choices in each session. The smoothed lines represent a running average of the choices (10 trial sliding window).

This figure was adapted from Stauffer et al. (2016)