Fig. 4

Reporting the activation of thalamo-cortical synapses in vivo. a Visual thalamus (dLGN, dashed area) transduced by GZ lentiviral vector. b magnified view of transduced dLGN. c GZ-expressing synapses in V1 cortex. d–f Magnified views of layers I, II–III, and IV showing GZ-expressing presynaptic boutons. g Illustration (left) and merged fluorescent images (right) of the V1 cortex with sites of GZ expression (green) and SB injection (red; dashed square indicates a typical field for SB uptake analysis; see also Supplementary Figs. 6, 8). h Time flowchart showing SB perfusion, sevoflurane anesthesia, and dark or dark/light exposure visual stimuli. i–l V1 layer IV from control animals kept in the dark (Ctrl; i, j) or exposed to light-pulses (light stimulated; k, l), showing GZ expression (i–k) and SB uptake (j–l). Insets are magnified areas from dashed boxes. Color bars on the right are fluorescence LUTs. m, n SB fluorescence histograms for unstimulated control (m; cyan bars; N = 233 synapses and N = 93 neighboring non-GZ⁺ areas, p _{ctrl-background} = 0.45, KS test) and light stimulated (n; red bars; N = 177 synapses and N = 92 neighboring non-GZ⁺ areas, p _{light-background} < 0.0001, KS test) GZ-expressing synapses, and for the corresponding background fluorescence (gray bars; same experiments as i–l). Inset n, cumulative distributions of synaptic SB uptake for data set in m, n (p _light-ctrl < 0.0001, KS test). o, p Population data from control and light-stimulated animals for synaptic GZ expression (o; N = 5, p = 0.93; two-samples permutation test) and activity (p; N = 5, p < 0.005; two-samples permutation test). Scale bars: 245 μm (a, c, g), 10 μm (b, d–f, i–l)