Behavioral training

Rats were trained on a reach-to-grasp pellet retrieval reach task for up to four weeks before surgery. Each rat was placed within a 30-cm x 30-cm x 53-cm Plexiglas box with a 1-cm-wide slot allowing access to a tray where food pellets were placed. Forelimb preference was determined at the beginning of the skilled reach task training. Rats were trained to reach through the slot, grasp a food pellet (45 mg; Bio-Serv. Flemington, NJ) located 2-cm away from the front edge of the box on a horizontal shelf, and bring the food pellet to the mouth (successful retrieval). Trials were recorded with a digital camcorder (framerate 29.97 Hz) for playback and analysis. Rats were required to obtain at least a 70% successful reach rate (60 trials per day) for three consecutive days (baseline behavior) before inclusion into the study. Throughout the duration of the study, food intake was monitored on a scheduled feeding regimen to encourage performance on the skilled reach task.