Rats' short-term memory for brief electrical stimulation of the ventral tegmental area of the brain

Short-term memory for brief electrical stimulation of rats' ventral tegmentum was assessed in a delayed conditional discrimination procedure in which trials began with a train of either low- or high-intensity stimulations. After a delay (i.e., retention interval) ranging from 0.01 to 4 sec, a lever was inserted, accompanied by a dim or a bright light. Lever-pressing was rewarded with food on low intensity-dim light and high intensity-bright light trials, but not on low-bright or high-dim trials. Discrimination ratios, based on relative responding on rewarded trials, indicated that subjects were able to remember the electrical stimulations, but that there was sometimes substantial forgetting after the 4-sec retention interval. The implications of these results for an understanding of the stimulus properties of electrical brain stimulation were discussed.