V_m of V1 cortical neurons exhibits depolarization and decreased variability as a function of arousal, with most depolarized and least variable V_m during locomotion. A, Example traces of V_m from a V1 layer 5 regular-spiking, putative pyramidal cell, pupil diameter, and locomotion speed. Inset 1 emphasizes V_m changes associated with the transition from stillness to locomotion. Inset 2 emphasizes the relationship between pupillary microdilations (arrows) and V_m depolarizations during stillness. Spikes are truncated in example traces to emphasize subthreshold behavior. B, Coherence between pupil diameter and V_m. Coherence is high at low frequencies (0.01–0.02 Hz), with a smaller secondary peak from ∼0.1–0.3 Hz, likely reflecting the tracking of pupillary microdilations by V_m. C, Cross-correlation between pupil diameter and V_m, showing a lag of ∼1 s between changes in V_m and associated changes in pupil diameter. D, Mean spontaneous V_m (expressed as a change in V_m from the most hyperpolarized V_m recorded during a session) as a function of baseline pupil diameter and sorted by locomotion status. E, V_m SD as a function of baseline pupil diameter and sorted by locomotion status. F, V_m Hilbert amplitude at 2–10 Hz and 50–100 Hz as a function of baseline pupil diameter and sorted by locomotion status. G, Density plot, pooling V_m values recorded from all cells in the dataset, encapsulating data shown in D and E. Each vertical slice of the plot is the probability distribution of ΔV_m (the difference between V_m in a recorded cell and the most hyperpolarized V_m recorded in that cell) in a given pupil diameter range. A more dispersed probability distribution is evident at smaller pupil diameters, while a narrower distribution is evident at larger pupil diameters. For pupil diameter bins in D–G, bin widths were chosen such that an equal amount of data fell into each bin (N = 8 animals, n = 10 cells; data are shown as mean ± 68% CI).