Figure 1.

Layer V Sharpens the Temporal Response to Whisker Stimulation

(A) Schematic of the experiment in anesthetized animals. In this as well as in other figures, ChR2-positive neurons are indicated in blue, ChR2-negative cells in grey.

(B) Representative traces from a layer II/III ChR2-negative principal neuron in vivo.

(B₁) Average response in (B) at a finer temporal scale.

(C and C₁) Peak amplitude (C) and area (C₁) in ChR2-negative layers II/III, V, and VI cells under the different experimental conditions. n = 39 cells from 17 animals; paired t test. In this as well as in other figures, values from individual experiments are shown in grey, the average of all cells in black. Error bars indicate SEM.

(D–D₃) Spiking response of a deep neuron under the different experimental conditions. Blue light was presented at different delays (~0 ms in D₁, ~30 ms in D₂, ~50 ms in D₃) from the onset of the whisker-evoked response.

(E–E₃) Peri-stimulus time histogram (black trace, bin 10 ms) of whisker-responsive deep cortical neurons during whisker stimulation (red bar, E) or during whisker stimulation followed by layer V activation (blue bar, E₁–E₃). Gray traces in (E₁)–(E₃) show the average peri-stimulus histogram shown in (E).

(F) Cellular spike rate in a time window of 100 ms from the onset of the whisker stimulation under the different experimental conditions shown in (E)–(E₃). n = 13 cells from 7 animals; Friedman test.

(G) Schematic of the experimental configuration.

(H and H₁) Raster plots showing the response of a representative deep cortical neuron to whisker stimulation (red bar) alone (H) and during concurrent layer V photosuppression (yellow bar, H₁).

(I and I₁) Peri-stimulus time histograms (black trace) of whisker-responsive deep cortical neurons recorded during whisker stimulation (red bar, I) and during whisker stimulation and concurrent layer V photoinhibition (yellow bar, I₁). The gray trace in (I₁) represents the average peri-stimulus histogram shown in (I).

(J) Spike rate in the early (0–40 ms) and late (40–100 ms) response window under the different experimental conditions shown in (I) and (I₁). n = 19 cells from 14 animals; early response, Wilcoxon test; late response, paired t test. In this as well as in other figures, *p < 0.05; **p < 0.01; ***p < 0.001. Error bars indicate SEM.

See also Figures S1–S4 and Tables S1 and S2.