Figure 3
Response of dorsal raphe serotonergic neurons to shock and light.
(a,b) Pixel-wise (a) and averaged (b) response in one fish. Light caused a decrease in activity, whereas darkness and shock caused an increase. (c–f) Effect of a 10-second light pulse on shock-evoked activity. Two 1-second pulses of shock were given 60 seconds apart and light was delivered 10 seconds after the second shock. (c) The response in one fish. (d) A single activity related cluster obtained from k-means clustering of the normalized data. (e) Cells in the raphe corresponding to the cluster shown in (d). (f) Time for shock-evoked fluorescence to drop to the minimum value, with or without delivery of light, in 10 fish. Circles represent the mean. Error bars are 95% c.i. (g–j) Response to gradually decreasing light. (g) Neurons are inhibited in the light and excited at the start of the decrease (red arrows) and close to darkness (black arrows). (h) Voltage applied to the LED (blue trace) and measured intensity (green trace). (i) Data compiled from three fish, each exposed to three trials (total of 9 trials). The red trace shows difference in intensity between two consecutive time points. The bold blue trace is the mean activity across 9 trials. The thinner lines represent resamples of the data obtained by 500 bootstrap iterations. There is a transient excitation following the large change in illumination. (j) Raster plots showing spike times obtained by temporal deconvolution of the mean calcium traces in each trial. The trials are sorted in ascending order of the half maxima. Black lines correspond to individual spikes of action potentials. The red diamonds indicate the half maxima of the second peak response to decreasing illumination. In 8/9 trials, the second response starts before the LED intensity turns 0. Red dashed line: time point with the large change in illumination. Grey dashed line: earliest half maxima. Bold black dashed line: time-point when the LED intensity was 0. p-value in (f) is based on Paired T-test. d is Cohen’s d. Scale bar = 25 μm.
