No rat dropped below 85% of initial ad libitum body weight at any time. Three naive rats were trained on the 1DR task (Figure 2C). Each session began with 400 trials where both sides were rewarded and then reward were provided only for one choice direction (when
correct) and this rewarded direction changed across blocks of 100 correctly performed trials (∼120–140 trials total). Reward were delayed for 1 s after entry into the water-port. We provided auditory feedback for both correct and error choices for both the rewarded and unrewarded sides. To ensure that rats responded to the nonrewarded direction following incorrect choices we repeated MEK inhibitor cancer the same stimulus in the next trial. Repeated trials were removed from the analysis. Go-signal paradigms were similar to reaction time paradigm except rats were required to stay
in the odor sampling port until a 2 kHz, 100 ms pure tone was delivered after delay dtone after odor valve onset ( Figure 3A). Otherwise, the task timing was identical to the low urgency version of the RT task ( Figure 1C). The following three conditions were considered invalid Tanespimycin purchase trials and were not rewarded and not counted in accuracy or OSD measurements: (1) short odor poke trials (withdrawal from the odor port before the go-signal) resulted a short white noise burst (120 ms) and 4 s increase in dintertrial. (2) Long odor poke trials (withdrawal >1.0 s after the go-signal) triggered a long white noise Digestive enzyme burst (3 s) and 4 s increase in dintertrial. (3) Delayed choice trials (failure to enter a choice port within 4 s after a valid odor sampling period) were invalid but not signaled in any way and did not result in any increase in dintertrial. In a first set of go-signal experiments (Figure 3), a single go-signal delay was used in each session and a range of odor mixtures (12% to 90% mixture contrast) were randomly interleaved within the session, as in the RT paradigms. Go-signal delays were changed from session to session while the odor stimuli
remained constant (Figure 3B). The set of rats tested in this paradigm were naive at the beginning of training. In a second set of go-signal experiments (Figure 4), a single odor mixture pair was delivered in each session and go-signal times were randomly varied within a session. In these experiments, a single set of four rats was used in five sequential phases (I–V). (I) A pseudorandom go-signal delay (dgo) for each trial was drawn from a uniform distribution (0.1–1.0 s in 0.1 s increments). Mixture ratio difficulty was increased after stable performance was achieved (8–10 sessions per ratio) ( Figure 4A, phase I). (II) dgo was drawn from an exponential distribution (mean 0.3 s) using the 12% mixture contrast stimuli ( Figure 4A, phase II). (III) Subjects were retested using uniformly distributed go-signal delays while keeping the same stimuli ( Figure 4A, phase III).