Fig. 2: Brief optogenetic stimulation of dopamine neurons in the VTA produces learned associations without endowing cues with cached value.
From: Dopamine transients do not act as model-free prediction errors during associative learning
Top row: Schematic illustrating the task design, which consisted of preconditioning and conditioning, followed by conditioned reinforcement and probe testing. A and E indicate visual cues, while C, D, F and X indicate auditory cues. R1 and R2 indicate differently positioned levers, and black circles show delivery of food pellets. VTA dopamine neurons were activated by light delivery in our ChR2 experiment group (n = 8) but not in our eYFP control group (n = 8), illustrated by the blue triangle, for 1 s at the beginning of X on AC trials and in the inter-trial interval on AD trials. Middle and bottom rows: Plots show rates of responding (with standard error of the mean represented above and below the mean; ± SEM) across each phase of training, aligned to the above schematic. The top row of plots show data for the eYFP control group and bottom row of plots show data for the ChR2 experimental group. For individual rats’ responses see Supplementary Fig. 3.
