Figure 4. Silencing visual cortex does not alter SC speed tuning or time course in response to looming in awake mice.

(A–B) Preferred speed analyzed by the mean (A) and peak (B) spiking rate, respectively. S_pref_weighted was calculated as described in Experimental Procedures. No significant alteration of the preferred speed was seen (p=0.77 in A and 0.56 in B, n=15, paired t-test). (C) Spontaneous spiking rates of SC cells before and after silencing cortex. A trend of slight reduction was seen, but not statistically significant in our dataset (p=0.21, n=15, paired t-test). The spontaneous spiking rates were 1.7±0.9spikes/s for control condition, and 0.8±0.5spikes/s when cortex was silenced (mean±S.E.M.). (D) Instantaneous spiking rate in the awake SC, averaged across all cells (bin width of 100ms; n = 15; black for the control, blue for silencing cortex, and light blue dashed lines for normalized blue curves to the control’s peak). The control and the peak-normalized responses after silencing cortex were only significantly different at the late phase of the lowest speed, as marked by pink shades (p<0.05, paired t-test). Note that responses to stimuli with different speeds were plotted with different time scales.