Extended Data Fig. 7: MEC is not required for all interval timing behavior.

a. Schematic for inhibiting MEC after learning in the tDNMS task. After experiments testing the role of MEC during learning (Fig. 4), a subset of mice (n = 7 DREADD, n = 10 Control) underwent extended training to determine whether MEC is necessary for ongoing task performance. b. Though MEC inhibition impaired learning in the tDNMS task (Sessions 1-8), DREADD mice learned the task in the absence of MEC inhibition (Sessions 9-14). Following learning, subsequent administration of DCZ to inactivate MEC did not affect performance in Sessions 15-16. Bars indicate mean performance ± s.e.m calculated across mice. c. Fixed interval task schematic. MEC DREADD (n = 9) and Control (n = 10) mice were trained on a fixed interval (FI) task (Toda et al. 2017). A droplet of water (4-6ul) was delivered every 10 s to head-fixed mice. Licking was measured; time-locked predictive licking indicates learning the timing of water delivery. The DREADD agonist DCZ (1 mg/kg) was delivered 5 min prior to each session. d. Licking behavior of DREADD (n = 9) and Control (n = 10) mice on sessions 1 and 5 of the FI task. Licking was normalized to the maximum lick frequency with each session for each mouse. All trials for all mice are shown; water delivery occurs at 0 s, indicated by a yellow line. Average lick response for each session is shown in white. e. Fixed interval learning. Predictive licking is defined as an increase in lick rate, measured over 5 seconds preceding the upcoming reward delivery. Both DREADD and Control mice learn the temporal structure of the task, as demonstrated though more frequent engagement in predictive licking from sessions 1-5. Data represent mean ± s.e.m. averaged across mice. f. Average time of peak predictive licking activity in FI task relative to upcoming water delivery. From session 1 to 5, peak predictive licking activity moves closer to reward delivery (0 s) for both Control (p = 2.2 × 10⁻⁴, two-tailed paired t-test) and DREADD mice (p = 0.0013 two-tailed paired t-test). Data points represent average time of peaking licking on Session 1 and 5 for each mouse; bars indicate mean ± s.e.m. across mice.