ACTIVE-AVOIDANCE LEARNING USING BRAIN-STIMULATION APPLIED TO THE INFERIOR COLLICULUS AS NEGATIVE REINFORCEMENT IN RATS - EVIDENCE FOR LATENT INHIBITION

The inferior colliculus has been implicated in aversive or anxiogenic aspects of defensive behavior. Animals learn to turn off electrical st imulation applied to the inferior colliculus. The purpose of the prese nt study was to determine (1) whether this aversion induced by electri cal stimulation can be conditioned to a conditioned stimulus (CS, ligh t) and (2) whether pre-exposure to the CS will diminish the extent of such conditioning, i.e. whether latent inhibition can be established w ith this paradigm. Rats were placed inside an open field, and threshol ds for the escape response to electrical stimulation of the inferior c olliculus were determined. The rats were then placed inside a shuttle box and submitted to a two-way avoidance paradigm. Electrical stimulat ion of the inferior colliculus at the escape threshold was used as neg ative reinforcement and shuttle box illumination as the CS. The rats q uickly learned to avoid or terminate the inferior-colliculus stimulati on. Furthermore, the performance of the animals in this paradigm was s ignificantly disrupted when they were pre-exposed to 50 presentations of the CS before the session. These data suggest that the inferior col liculus has neural substrates for supporting associative learning and latent inhibition.