Figure 1.

Task and infusion protocol. A, Odor–interval associations. Rats were trained to indicate how much time had elapsed since the previous trial by selecting the odor associated with that specific time interval: Odor A for a 1 min interval, Odor C for a 12 min interval, and Odor B for the variable-length intermediate interval. The correct odor cup contained a cereal reward buried in the sand. B, Example session testing intervals of 1, 3, and 12 min. In the depicted example, the rat is offered a choice between Odors A and C (i.e., 1 vs 12 min comparison), while Odor B is covered. Odor C is rewarded since the previous trial occurred 12 min before. C, Sample behavioral schedule for one rat. Rats were tested on each condition for four daily sessions, counterbalancing infusions of saline (SAL) and fluorophore-conjugated muscimol (FCM) over consecutive days.