Fig. 2.

Sound-evoked corticocollicular axon response increases monotonically with sound level and remains stable over 1 week of imaging. a A chronic preparation for epifluorescence imaging of GCaMP6s in CCol axons via a cranial window (scale bars = 0.5 mm) in awake, head-fixed mice. Red rectangle denotes region of interest for CCol imaging. L is lateral and C is caudal. Mouse schematics in Figs. 2a, 3a, and 4a are adapted with permission from Aronoff et al., 2010⁶⁹. All rights reserved. These images are not covered under the CC BY license for this article. Scientific data and content are original. b Time course of mean fractional change in the CCol response amplitude evoked by a 50 ms white noise burst from a single imaging session. Gray box denotes stimulus timing and duration. c The monotonic growth of CCol peak response amplitude falls off steeply when the region of interest is shifted away from the IC. Data represent mean ± SEM. d Top: CCol response growth functions from a single mouse across seven daily imaging sessions. Data represent mean ± SEM. Bottom: Scatterplots depict the mean CCol response amplitude (x-axis) at each sound level measured from the first two imaging sessions (defined as baseline) against the CCol response amplitude (y-axis) measured on the day specified. The slope (m) of the linear fit provides an estimate of daily changes in response gain, where m = 1 indicates a matched response growth relative to baseline, m < 1 indicates a divisive flattening of the growth function and m > 1 indicates a multiplicative enhancement relative to baseline. Shading represents the 95% confidence interval of the fit. e As per d, averaged across all control mice (n = 5)