a, Coronal slice schematic; black square, area of AAV1-Syn-FLEX-GCaMP6s injection in ChAT-Cre mice into basal forebrain (AP: -0.5 mm from bregma, ML: 1.8 mm on right side, DV: 4.5 mm from surface). b, Proportions of GCaMP+/ChAT-, GCaMP+/ChAT+ and GCaMP-/ChAT+ cells (n=3 mice, 15 images, 174 cells). c, GCaMP6s expression in nucleus basalis. d, ChAT immunohistochemistry in same region. e, Overlay showing co-localization of GCaMP6s, ChAT. f, Decoding stimulus based on cholinergic terminal activity is effective only during tone period (stimulus: pre-tone, p=0.95; tone, p=0.04; post-tone, p=0.18; Student’s t-test). g, Decoding action (i.e., licking or no licking) could be predicted by cholinergic terminals even before the tone (pre-tone, p=0.06; tone, p-0.01; post-tone, p=0.04; Student’s t-test). h, Behavioral outcomes with saline applied to auditory cortex. i, Behavior with atropine applied to auditory cortex.