Figure 6.

Optogenetic suppression of VIP⁺ cells alters SF and orientation tuning. A, Top, Coronal section of a VIP-Cre x tdTomato mouse injected with a FLEX-ArchT-GFP. The native expression of tdTomato is shown in red; ArchT-GFP-expressing cells (anti-GFP immunostaining) are shown in green. Bottom, Overlaid image (green + red) and a magnified area of the green rectangle. B, Example of whole-cell patch-clamp recordings in slices from the above mice. Illumination settings were similar to in vivo experiments (see Materials and Methods). C, Example of in vivo Ca²⁺ responses evoked after suppression of VIP⁺ cells, presumably by the rebound firing of VIP⁺ cells that occur after photostimulation. Gray shaded area denotes photostimulation frames (2 s; emission was collected in this example with a 535/50 nm filter, therefore frames during photostimulation were zeroed for presentation purposes due to light artifact). D, Top, In vivo light-induced network response (n = 93 cells, 9 trials). Photostimulation lasted 1.4 s. Bottom, Averaged response across cells. E, Imaging protocol. On interleaved trials, visual stimuli were presented either with photostimulation (red; LED-on) or without (control) in a pseudorandom order (block randomized). Visual stimuli lasted 670 ms; LED pulses were locked to visual stimuli and lasted 1.4 s; the interval between stimuli was 4 s. F, Ca²⁺ responses of 10 putative pyramidal cells during visual stimulation and photostimulation. Top, Visual stimuli are shown in black (670 ms) and photostimuli in pink (1.4 s; for photostimulation artifact removal, see Materials and Methods). G, Tuning matrix and SF tuning curves of two example cells. Left and middle, Matrices of the evoked responses to each stimulus under control and LED-on conditions, respectively. Red arrows point to the preferred direction. Right, SF tuning curves fitted with DOG. H, Top, Histograms of the cells' preferred SF in control (blue) and LED-on (red) conditions (n = 99 cells). Bottom, Confusion matrix showing a decrease in the cells' preferred SF upon VIP⁺ suppression. I, Top, Scatter plots from an example network showing the response peak of the SF tuning curves fitted with DOG in control and LED-on conditions (n = 76 cells; only cells with 95% confidence interval <1.5 octaves were included in this analysis; see Materials and Methods). Each circle represents a cell; cross represents population average. Black circles depict cells with a significant change in their response amplitude to any stimulus and gray circles depict cells with no significant change (p < 0.001, t test with Bonferroni multiple-comparisons correction). Bottom, Histogram of the SF response peak pooled into 7 bins, each 0.01 cpd wide, in control (blue) and LED-on (red) conditions. J, Population mean of the SF response peak estimated by DOG. Data are pooled from five animals: four anesthetized and one awake (black line). K, Scatter plots comparing orientation tuning parameters in control and LED-on conditions. Shown are the response amplitude (ΔF/F) to the preferred direction (Pref) and OSI.