Fig. 5: Testing the prediction that VTA photostimulation-induced movements are goal-specific and context-dependent.

a Schematics of electrode implantation in the medial forebrain bundle (MFB) and injection of the ChR2-YFP-expressing virus and fiber implantation in ventral tegmental area (VTA). b Experimental test of the model predictions. A location is rewarded by MFB electrical stimulation (left). Then (inside the brackets), VTA photostimulation is provided in the context where reinforcement occurred (R. context) and in another context (no R. context, where no location had been rewarded). Each condition is compared to controls without acute VTA photostimulation (for R. context : MFB+YFP animals ON light, and MFB+Chr2 animals OFF light; for No R. context : Chr2 animals OFF light). c From left to right : example trajectories at the end of the MFB conditioning sessions, and post-photostimulation bouts of trajectories in the different conditions described in c. Differences between photostimulation-rewarded location delays for YFP (reward context, R/YFP ON versus OFF, paired t-test T₍₇₎= −0.07, p = 0.94); ChR2-expressing (reward context, T₍₁₀₎= −3.58, p = 0.05) and ChR2-expressing (no reward context, T₍₈₎= 0.32, p = 0.76) animals. d Cumulative distribution of the photostimulation-rewarded location delays in YFP (ON versus OFF light in reward context, Kolmogrov–Smirnov test on all trials from all mice: p = 0.23); ChR2-expressing (Reward context, KS test: p = 1.10⁻⁸) and ChR2-expressing (no-Reward context, KS test: p = 0.81) animals. e–k. Speed (e), distance to the rewarded location (g), and angle between the animal and the rewarded location j around VTA photostimulation (blue shading) for ChR2-expressing animals when ON light in reward context (purple), OFF light in reward context (light blue) and ON light in no reward context (red). Average difference in speed (f), distance to the rewarded location (h), and angle between the animal and the rewarded location (k) between ON and OFF light conditions, in reward (“R-ChR2”, ON versus OFF paired t-test after stimulation for speed: T₍₁₀₎=3.46, p = 0.006, distance: T₍₁₀₎=−3.68, p = 0.004, angle: T₍₁₀₎=−5.32, p = 3.10⁻⁴) and no reward (“No-R ChR2”, speed : T₍₈₎=−0.17, p = 0.87, distance: T₍₈₎=−1.17, p = 0.27, angle: T₍₈₎=−0.89, p = 0.40) contexts. i shows the computation of angle between the animal and the rewarded location, based on the same trajectories as in (a), realigned to the same line relative to the rewarded location, showing straight trajectories for animals when ON light in reward context (purple), and indirect trajectories when OFF light in reward context (light blue) or ON light in no reward context (red).Data are presented as mean ± s.e.m. See also source data file.