(A, D) Entropy of the distribution of the retinal fed experimental flies (red) and non-retinal fed control flies (blue) in the behavior space relative to the timing of red light stimulus onset (red light turned on at t = 0 s, the time of red light activation is indicated by dashed lines). The behavior space for experimental flies shows reduced entropy when the flies perform a specific set of behaviors, because flies shift from the full range of normal fly behaviors to a subset of red light-activated behaviors. (B, E) Average density ± the standard deviation in the head grooming map region indicated in red (inset, upper right) in experimental flies (red) and controls (blue) relative to red light activation. The head grooming region was calculated as the region in the map that experienced a statistically significant shift in density in experimental flies but not controls when comparing the first 3 s (green bar) of the activation period to the last 15 s of the recovery period (Wilcoxon rank sum test, p<0.05, using the Dunn–Šidák correction for multiple hypotheses). (C, F) Average density in the map over a series of 3 s windows (calculated from six animals, 30 trials each). Red and blue indicate regions of high and low density, respectively. The time ‘before’ stimulus onset is the average of 30 time periods between stimulations. We found an increase in the amount of ‘Idle/Slow’ dynamics for experimental flies in the interstitial times between stimulations. Thus, the differences between experimental and control animals in the time ‘before’ stimulation most likely reflects this increase in the amount of Idle/Slow behavior for experimental animals in the time between stimulation.