Fig. 1: Head-fixed probabilistic Pavlovian conditioning combined with tetrode recording and optogenetic tagging.

a Schematic diagram of the task protocol. After a variable foreperiod, in which the animals were not allowed to lick, they were presented with two cues, either predicting likely reward or likely punishment; reinforcement was preceded by a short, variable delay period. Created using Mathis, M. (2020), Classical Conditioning Mouse, Zenodo, https://doi.org/10.5281/zenodo.3925907, under Creative Commons 4.0 license (https://creativecommons.org/licenses/by/4.0/). The original image was not modified. b Raster plot of mouse licking times aligned to stimulus (cue) onset from an example session, showing higher anticipatory lick rate in response to the reward-predicting cue (Cue 1). c Lick rates (peri-event time histograms, PETH) aligned to stimulus onset from the same example session. d Average lick rates of all recording sessions in which BFPVNs were identified (n = 25 sessions; errorshade, SEM). e Average lick rates of the same n = 25 sessions as in (d), partitioned according to the four possible outcomes (errorshade, SEM). f Histological reconstruction of the tetrode track in the HDB. Green, ChR2-eYFP; magenta, DiI. Top right, magnified image of the electrolytic lesion site (white arrowhead) from a different section, indicating the tip of the electrodes. MS, medial septum; VP, ventral pallidum. Repeated in n = 4 mice. g Locations of the recorded BFPVNs based on histological reconstruction. Different markers correspond to different mice. Numbers show antero-posterior positions relative to Bregma. h Schematic illustration of viral injections, extracellular tetrode recordings and optogenetic tagging in mice. Created using Kennedy, A. (2020), Mouse brain silhouette, Zenodo, https://doi.org/10.5281/zenodo.3925919, under Creative Commons 4.0 license (https://creativecommons.org/licenses/by/4.0/). The original image was modified by adding illustrations of a syringe and an electrophysiological drive as well as additional legends. i, Example raster plot of spike times aligned to photostimulation pulses of an optogenetically identified BFPVN. j Firing rate (color-coded PETH) of all optogenetically identified BFPVNs aligned to photostimulation onset.