Figure 6.

Delayed response task for head-fixed rats. (A) Apparatus used for experiments with head fixation (Left, top view; right, side view). A rat is laid in a prone position with its head fixed and body loosely restrained in a half-cylinder acrylic chamber. (B) Sequence of task events in a trial. At the beginning of a trial, an LED, either on the left or right, is illuminated for a short time then turned off. After a delay period, two spouts protrude towards the mouth of the rat. The correct response is to lick the same direction as the LED illuminated before the delay. The duration of the delay was typically 2 s for single-unit recording. Correct responses are rewarded with a drop of sucrose from the spout. Prior to the behavioral training, the head fixation device was implanted under anesthesia. After a period for recovery from the surgery, rats were habituated to the head-fixation condition by giving free reward from the spout. Then, the rats were trained in the delayed response task. As they performed about 300 to 400 trials per day, the correct rate gradually increased and reached over 80% in 2 or 3 weeks.