Fig. 1: Distribution of TC synapses along the dendrites of in vivo recorded PTs.

a Top-Left: we labeled in vivo recorded neurons in the barrel cortex (vS1) with Biocytin in adeno-associated virus (AAV) injected anesthetized rats (N = 26). Bottom-left: AAV injection example into ventral posterior medial thalamic nucleus (VPM). The schematic of the rat was adapted and modified with permission from “Rhythmic whisking by rat: retraction as well as protraction of the vibrissae is under active muscular control. Berg RW & Kleinfeld D. J Neurophysiol 89, 2003, page 105.”⁶⁷. Top-right: image of the barrel field in layer 4 of vS1 shows AAV-infected thalamocortical (TC) axons corresponding to the injection site on the left. Bottom-right: expression of the vesicular glutamate transporter 2 (VGlut2) corresponding to the top panel image. b 3D reconstruction of dendrites (red) and TC synapses (green) of the PT example shown in Supplementary Fig. S2a. Zoom-ins show super-resolution images of dendritic spines (red) on the basal (bottom) and apical dendrites (top) that were in contact with AAV-infected TC boutons (green) and which co-expressed VGlut2 (cyan). The arrows denote the locations of the hence identified TC synapses. c Density of TC synapses along the dendrites of three PT examples (see Supplementary Fig. S2c for complete gallery). d We aligned PTs by the BP and plotted TC synapse densities (mean ± SEM) along the basal and apical oblique dendrites (gray), and the apical trunk and tuft dendrites (green). e BP locations correlated significantly with the location of the highest TC synapse density (Pearson R = 0.8, p = 0.005). Please note: we chose the color maps in panels a/b to increase visibility. Fluorescent labeling was Alexa-405 for VGlut2, Alexa-488 for biocytin and Alexa-647 for AAV. Source data for panel (d) are provided in the Source Data file.