Figure 7. Spike firing patterns of individual LHb neurons in a reward Pavlovian conditioning task.
(A) The schematic of setup for recording from LHb Vglut2-expressing neurons in a freely-behaving mouse. (B and C) Identification of a Vglut2-expressing neuron using optical tagging. The arrow in (B) points to the electrolytic lesion site targeted by an optotrode from a representative Vglut2-LHb-ChR2-mCherry mouse. Red, ChR2-mCherry. Blue, DAPI counterstaining of cell nuclei. The peri-event time histogram (PETH, bin width = 50 ms) in (C) shows that trains of light pulses (5 ms, 10 Hz) transiently and reliably evoked spike firing from a single unit. (D) Spike firing pattern of a representative LHb neuron (the same one shown in C). Upper panel, heatmap representation of the spike firing rates within the fourth daily session of Pavlovian reward conditioning. The color scale indicates the range of firing rates (spikes/s). Lower panel, PSTH of the mean firing rates (smoothed with a Gaussian kernel with σ of 50 ms). (E) The firing patterns of individual Vglut2 neurons (n = 70 optically-tagged cells). The standardized spike firing rates are represented as heatmaps. Each row represents the firing pattern of a single unit aligned to the cue onset. Principal component analysis indicates that the firing patterns cluster into two major subtypes. (F and G) Mean standardized firing rates of the Type I (F) and the Type II (G) response patterns of LHb neurons. Thick lines indicate the mean and shaded areas indicate the SEM. Red and blue segments indicate statistically-significant increases and decreases from the baseline, respectively (p<0.05; multivariate permutation test).
Figure 7—figure supplement 1. Identification of LHb neurons and the overall response pattern in a reward Pavlovian conditioning task.
