a, Location and depth of recording sites in the dmPFC and number of neurons recorded (n = 7 mice). b, Top: superimposed waveforms recorded from three different units. Bottom: spikes originating from individual units were sorted using three-dimensional principal component analysis. c, Among the population of neurons recorded, 86% were classified as putative projection neurons (PN, red circles, n = 290) and 14% as putative interneurons (IN, blue circles, n = 48) using an unbiased unsupervised cluster separation algorithm based on three electrophysiological properties: firing frequency, spike half width (SHW) and spike area under waveform peak. Inset, average waveform of a representative PN and interneuron illustrating the methodology used to quantify SHW and the spike segment used to calculate the spike area under waveform. d, Top: representative cross-correlogram performed between a PN and interneuron showing a short-latency, presumably monosynaptic, excitatory interaction (no inhibitory interaction identified among all significant cross-correlograms identified). Bottom: representative cross-correlogram between an interneuron and a PN showing a short-latency, possibly monosynaptic, inhibitory interaction (no excitatory interaction identified among all significant cross-correlograms identified). Reference events correspond to the spikes of the presynaptic neuron (dashed line at time 0, bins of 0.5 ms). Red and blue circles represent PNs and interneurons, respectively. e, Box plot of the firing rate of PNs (n = 290 in 7 mice) and interneurons (n = 48 in 7 mice). For each box plot, the middle, bottom and top lines correspond to the median, lower quartile and upper quartile firing rates. Blue and red dots below and above the boxes correspond to outlier data points. f, Corresponding firing frequency statistics for PNs and interneurons.