Subjects were five male Ruxolitinib mouse Long-Evans rats (Charles Rivers Laboratories, Wilmington, MA). Rats were singly housed in a 12:12 hr light:dark cycle with ad libitum access to water. After arriving in the colony, animals were handled several days per week until the beginning of behavioral training. Prior to training, rats were
placed on a feeding schedule to maintain body weight at 85%–90% of free feeding weight. All procedures were in accordance with the appropriate institutional animal care and use committee and NIH guidelines for the care and use of animals in research. The apparatus, the Floor Projection Maze (Figure 1A), consisted of an open field (81.3 × 81.3 cm) in which images were back-projected to the floor and the position of the animal was tracked from above (Furtak et al., 2009). Computer controlled pumps provided food reward
(2% fat chocolate milk) to four reward ports. The maze was interfaced with integrated systems for location tracking, neuronal data acquisition, and behavioral control. Rats were trained on a discrimination task in which pairs of 2D visual stimuli were presented on the floor of the exploratory maze. Stimuli were well within the limits of visual acuity for Long-Evans rats (Douglas et al., 2005; Furtak Ulixertinib concentration et al., 2009). In all phases of shaping and training in which two objects were presented, the left versus right location Rebamipide of the correct stimulus was counterbalanced. Animals were shaped
in a number of steps indicated in Table S1. The final stage of shaping was exactly the same as the final task and differed only in the stimuli and the number of problems. Once an animal reached criterion (8 out of 10 trials correct for two consecutive days), the animal was advanced to the object discrimination task. Animals were trained on two discrimination problems, each consisting of a pair of stimuli. Each stimulus was a high contrast, circular pattern. For each problem, the two stimuli were matched for area of light and dark. The two problem pairs differed in contrast and the ratio of light area to dark area (Figure 1D). Animals began with 10-trial blocks alternating between the two problems for 100 trials. Once an animal reached criterion, 10 consecutive correct trials over 2 blocks, the electrode array was implanted. Following surgery, animals were retrained on blocked trials for 100 trials per day. Recording was initiated as soon as rats were reliably performing the task. When animals were performing at >75% correct, they were given 100 trials per day of randomly-interleaved presentations of the two problems. If performance dropped, rats were returned to blocked trials until accuracy improved. Recordings were obtained on both blocked and random presentation of stimuli.