Effect of foot-shock intensity on amount of memory retrieval in rats by emotionally important stimuli in a drug-dependent learning escape design

Abstract

Drug-dependent learning (lack of transfer between drug states) was demonstrated and disrupted in an escape learning, forced choice T-maze task. A drug-dependent learning (DDL) group was trained to escape foot shock (0.65 mA) while in a drug (chlordiazepoxide hydrochloride) state. These rats subsequently responded randomly on non-shock test trials in the non-drug state, but continued to respond significantly (P less than 0.02) above random level when in the training drug state. Four transfer groups were also trained in the Drug state, but with a 1 kHz auditory tone simultaneously paired with foot shock. Each Transfer group received a different (0.10, 0.65, 3.5, and 4.5 mA) foot shock intensity during training. The auditory tone continued to be sounded during testing with no foot shock, and percentage correct turns, first-trial correct turns, and latency scores were significantly (P less than 0.01) different from the DDL group's performance. The results were interpreted as demonstrating that an emotionally-important auditory stimulus could initiate a memory retrieval process that could overcome a physiological state. This memory retrival process was not modified by wide variations in foot shock intensity.