(A) Timeline for measurement sessions (black text) and procedures (gray text) performed in each of 11 ChAT-Cre-Δneo × Ai148 mice. Basal forebrain cholinergic neuron (BFCN) responses to unconditioned auditory and visual stimuli described below were measured during test session 2. (B) BFCN responses to drifting visual gratings of varying contrast (left) and auditory spectrotemporal ripples of varying sound levels (right) are shown for an example mouse. Heatmaps depict fractional change values for individual trials in horizontal limb of the diagonal band of Broca (HDB) (top row) and GP/SI (bottom row). Line plots depict mean ± SEM z-scored fractional change across all trials. Vertical bars denote onset and offset of the 2 s stimulus period. (C) Evoked response amplitudes to auditory and visual stimuli in HDB (left column) and GP/SI (right column). Circles denote individual mice (N = 11 for all conditions), bars denote sample mean and SEM sensory response amplitudes. Responses at variable stimulus intensities are averaged across horizontal/vertical visual orientations (top), upward and downward auditory frequency modulation (middle), and low, middle, and high auditory pure tone frequencies (bottom). Refer to Figure 2—figure supplement 1 for a comparison of responses to each direction of visual and auditory stimulus change. Sensory-evoked cholinergic responses to visual gratings and auditory ripples increase with intensity and contrast, but are stronger overall in GP/SI, particularly in the auditory modality (three-way repeated measures ANOVA with structure, stimulus level, and modality as independent variables: main effect for structure, F = 10.09, p = 0.01; main effect for stimulus level, F = 63.52, p = 2 × 10–9; main effect for modality, F = 20.83, p = 0.001; modality × structure × level interaction term, F = 9.1, p = 0.002). Asterisks denote a significant difference in the peak post- and pre-stimulus response (paired t-test, p < 0.05, corrected for multiple comparisons). Black and gray horizontal bars denote significant and non-significant differences, respectively, in sensory-evoked response amplitudes between HDB and GP/SI (paired t-test, p < 0.05, corrected for multiple comparisons). (D) Mean ± SEM normalized pupil dilations evoked by 70 dB SPL auditory ripples significantly decreased over 20 presentations (one-way repeated measures ANOVA, F = 2.85, p = 0.0003; N = 7 mice). Inset: Mean sound-evoked pupil diameter change in an example mouse for trials 1–3 vs. 11–20. Inset scale bar = 1 z-score and 2 s and applies to all inset panels below. Vertical dashed line = onset of the 2 s stimulus. (E) Mean ± SEM normalized BFCN response to auditory ripples were significantly and equivalently reduced in HDB and GP/SI over 20 presentations (two-way repeated measures ANOVA with structure and presentation number as independent variables: main effect for structure, F = 0.51, p = 0.49; main effect for presentation number, F = 6.11, p = 5 × 10–12; N = 11 mice). Insets: Mean response from an HDB fiber of an example mouse for trials 1–3 vs. 11–20. Figure 2—figure supplement 2 presents habituation functions for other auditory and visual stimulus types at varying stimulus intensities. (F) Mean ± SEM normalized BFCN spontaneous GCaMP transient amplitudes did not change over 20 measurement blocks (two-way repeated measures ANOVA with structure and presentation number as independent variables: main effect for structure, F = 0.80, p = 0.70; presentation number × structure interaction term, F = 0.57, p = 0.93; N = 11 mice). Insets: Spontaneous transients from an HDB fiber in two trials for which no stimulus was presented.