Fig. 3.

Optogenetic photoinhibition of ChAT interneurons enhances MSN spiking in vivo. (A) (Top) Voltage trace of an isolated unit (recorded from the NAc in vivo) that was excited by optogenetic photoinhibition of the ChAT interneurons with eNpHR3.0. (Middle) Raster plot displaying the response of the same unit to five repetitions of the light stimulation, with each action potential represented by a dot. (Bottom) Average and SEM of the firing rate over time for the same unit. (B) Wavelet analysis reveals power of spiking as a function of frequency and time (average across five repetitions) for the same unit as in (A). (C) Fraction of sites that were inhibited versus excited by light stimulation. (D) Sameas (A), for a unit that was inhibited by light stimulation. (E) Population summary of the time course of response to light stimulation for sites that were inhibited (left; n = 13 of 17) or excited (right; n = 4 of 17) by light. Solid lines represent the average firing rate across sites as a function of time; each dot represents the average firing rate of an individual site. All firing rates are normalized to the mean value before light stimulation. (A to E) Duration of photostimulation, 15 s (constant illumination); wavelength, 560 nm. Epochs of light stimulation are represented by yellow bars.