(a) Example LC recording with pupil tracking. Left: LC spike raster separated by trial types. Right: Mean pupil diameter (± s.e.m.) separated by trial types. Gray and black arrows indicate tone and stimulus onsets, respectively. Gray and black bars indicate the time windows during which pupil responses to tone and to Go (behavioral responses) were quantified, respectively. We note that based on the temporal profiles of pupil diameter in different trial types (i.e., in the presence or absence of tactile stimulus or licking) and that the tactile stimulus starts 1 s after tone onset, pupil responses to tone and Go can be segregated (Materials and methods). (b) Top: Grand average cross-correlogram between LC spike train and pupil diameter (n = 39). Individual LC spikes were convolved with a 400 ms wide Gaussian kernel. Spike times were shuffled and LC–pupil correlations computed to establish controls (narrow gray band around zero). Bottom: Histogram of peak correlation coefficient (left), and time lags (right) between LC spike train and pupil diameter for each paired recording (magenta dot: mean). Both distributions are significantly larger than 0 (peak correlation coefficient: 0.15 ± 0.02, p=8.3e-7, signed rank = 743; time lags: 2.61 ± 0.39 s, p=7.8e-7, signed rank = 744, n = 39). (c) Grand average trial-aligned LC spike rate (n = 43, top), and pupil diameter (n = 36, bottom) averaged by different trial types. Gray and black arrows indicate tone and stimulus onsets, respectively. In Hit trials, the latency of LC responses to tone onset was 0.064 ± 0.005 s, and to whisker stimulation onset was 0.111 ± 0.008 s, and the reaction time (first lick latency to whisker stimulation onset) of the mice was 0.58 ± 0.03 s. (d) Left: LC responses to tone (T) and Go responses (G) during Hit trials with median indicated. Tone vs. Go: 4.79 (3.70–6.66) sp/s vs. 4.68 (3.33–7.26) sp/s, median (IQR), p=0.24, signed rank = 496.5, n = 43. Right: Pupil responses to tone and Go responses during Hit trials with median indicated. Tone vs. Go: 0.003 (−0.015–0.015) mm vs. 0.027 (−0.010–0.063) mm, median (IQR), p=6.4e-5, signed rank = 559, n = 36. Gray lines indicate individual recordings. (e) Top: Pre-stimulus (baseline) and post-stimulus (evoked) LC spike rate for Hit and Miss trials with median indicated (Baseline: Hit vs. Miss, 0.66 (0.30–3.51) sp/s vs. 1.55 (0.68–3.00) sp/s, median (IQR), p=0.0083, signed rank = 254.5; Evoked: Hit vs. Miss, 3.24 (1.78–5.49) sp/s vs. 1.82 (0.95–3.45) sp/s, median (IQR), p=5.5e-7, signed rank = 782.5, n = 43). Gray lines indicate individual recordings. Bottom: Histogram of choice probability for Hit vs. Miss trials based on baseline and evoked LC activity (magenta dots: mean). Choice probabilities are significantly deviated from 0.5. Baseline: 0.47 ± 0.014, p=0.032, signed rank = 295.5; Evoked: 0.59 ± 0.017, p=4.6e-6, signed rank = 751, n = 43. (f) Lick-aligned LC spike rate (top) and pupil diameter (∆Pupil, bottom) averaged by trial types: Hit (blue), FA (green).