Auditory Cortex Distinguishes between Spontaneous and Sound-Evoked Movements.

Activity in sensory cortex is influenced by multiple factors beyond sensory input, including body movements, neuromodulatory signals, and internal states such as arousal. Focusing on brief whisking bouts that occur independently of locomotion and which are a reliable indicator of cholinergic and noradrenergic input to the cortex, we investigated how these factors shape activity in the auditory cortex. By tracking the movements of individual whiskers in male and female mice, we observed that whisking events co-occur with subtle whole-body "twitches" and are followed by a dilation of the pupil that scales in size with the whisker movement. Although this behavior occurred spontaneously, near-identical whisker movements could also be elicited by pure tones. Whisking was reliably triggered by moderately loud, 80 dB SPL, tones at frequencies within the most sensitive region of the mouse's hearing range, with measurable whisker movements following tone presentation at levels as low as 50 dB SPL. Tone-triggered whisking was sensitive to the recent stimulus history but did not habituate over longer time periods. The activity of a subset of neurons in the auditory cortex was significantly modulated in relation to spontaneous whisking events. Surprisingly, many of those neurons did not respond or responded differently when whisking was sound triggered, suggesting that the context and the underlying driver of a body movement determine whether and how it modulates auditory cortical activity.