FIGURE 2.

Illustration of how a rat completes one trial in the 2-choice reaction time task. Briefly, a snout poke into the center hole initiates a trial. The rat needs to hold its snout in the center hole until either the left or right stimulus light (randomly) turns on (e.g., the right stimulus light turns on in this figure). The holding period is referred to as hold time. Upon the illumination of the stimulus light, the rat needs to enter the water dispenser (a large hole) under the stimulus light to obtain a drop of water within a certain period of time (i.e., the allowed maximal reaction time). An incorrect response (entering a water dispenser not associated with the illuminating stimulus light) will terminate the trial; an extremely slow response (occurring when reaction time > the allowed maximal reaction time) will be considered an omission, with no water reward delivered.