g., Ennaceur et al., 1996, Bussey et al., 2000 and Winters and Bussey, 2005) and thereby would provide an independent test of the effects of our lesions on behavior. Apparatus. The testing box included a CRT computer monitor immediately adjacent to a transparent enclosure that was integrated with a standard vivarium rat cage ( Figure 1). During testing, the rat’s home cage was attached to the

testing box permitting the rat to enter the testing box to request and Selleckchem 17-AAG complete trials or to return to the home cage to sleep or eat. The rat could obtain water only by correctly responding on training trials. The testing box was fitted with three ports. Each port contained an integrated infrared beam-break detector. Behavior (licking a port) was detected by an infrared beam break and water reinforcement could be delivered directly to either the left or right port. The three ports were spaced equidistant from each other (9.4 cm) across the front of the transparent enclosure and immediately in front of the computer monitor (left-center-right).

The rat initiated a trial by licking the center port. When a rat requested a trial a pure tone (500 ms, 750 Hz) was presented along with two visual stimuli (the S+ and S−). The two stimuli were presented directly behind the left and right response ports. The stimuli remained displayed until the Selleckchem FG-4592 left or right port was licked. Correct responses (i.e., licking a port in front of the S+) were rewarded with a pure tone

(500 ms, 1.5 kHz) and delivery of approximately 16 μl of water. Incorrect responses (i.e., licking the port in front of the S−) immediately blanked the monitor and initiated a brief timeout interval (range 2–6 s) such that licking the center port did not initiate a new trial. Rats were trained for 2 hr each day (7 day/week). Proprietary Matlab routines controlled all aspects of the training protocols, timing variables, stimulus and reward presentations, and collection of behavioral response data ( Meier et al., 2011). Training protocol. First, a series of shaping steps were presented so that the rats learned to retrieve water from the ports, request trials, and ultimately acquire a two-choice visual discrimination problem (two distinct black and white photographs). Mephenoxalone After this shaping phase, a new discrimination problem (black and white photographs of a paintbrush and a flashlight) was presented. The two images were scaled to equal size and matched for luminance and contrast (all pixel luminance distributions were matched). The two images were presented in grayscale against a black background on a linearized CRT monitor. This discrimination problem was used for the remainder of testing. The stimulus that served as the S+ was counterbalanced across rats. The S+ was equally likely to be presented on the left or right though this could be adjusted to overcome a response-side bias (for details see Meier et al., 2011).