Figure 1.

Pavlovian conditioning methods. The timeline of two possible consecutive trials is shown. An upward deflection of the trace indicates the period when a particular stimulus is on, and the number pointing to the deflection reflects the duration of the stimulus (durations for CS+2 and UCS are not to scale). CS+1 and CS– represent auditory tones, and CS+2 represents the brief feederclick sound. The UCS time represents the point in time at which the animal's tongue contacts the sugar pellet. Trials are spaced on a 2 min, variable interval, and the order of the tones is unpredictable.