Fig. 5.

Nonmonotonic effects of pupil-related state. A: spike raster of 1 neuron’s response to a single ferret vocalization sorted by time (top) and pupil size preceding the stimulus (bottom). A nonmonotonic relationship is evident between pupil size and spontaneous firing rate. B: examples of segmented regression model fits to spontaneous and driven activity for 3 neurons. Each point represents spike rate for 1 neuron on 1 trial (spontaneous activity: 2 s; driven activity: 3 s). Bottom row displays data from the neuron in A. C: results of test for nonmonotonicity using segmented regression model, counting the number of neurons with significant or trends toward nonmonotonic changes in baseline or gain. Inverted U, neuron with maximum firing rate at intermediate pupil sizes and lesser firing rate at small and large pupil sizes; U, neuron with a minimum firing rate at intermediate pupil sizes.