Body temperature cues as contextual stimuli: Modulation of hypothermia-induced retrograde amnesia

Abstract

Three experiments investigated whether the retention of passive avoidance training after the induction of amnesia by hypothermia could be modulated by the presence or absence of cold body temperature cues. In Experiment 1A, the cues for recovery from amnesia produced by a recooling treatment were erased by a 5, 10, or 15 min, but not by a 1 min, immersion in normothermic water. Similarly, Experiment 1B noted the erasure of the recooling reactivation effect by a 10 or 20 min immersion in normothermic water immediately after the recooling episode. In neither of these experiments did the rewarming treatment artifactually increase the activity of control animals. That the presentation of cold body temperature cues after an erasure treatment would again provide access to the target memory was also suggested in Experiment 1B. Experiment 2 confirmed this effect; over multiple test sessions animals displayed recovery from amnesia, erasure of the recovery effect, and recovery from erasure, in accordance with the availability of cold state cues. Multiple test sessions produced no memory recovery in control animals. Reactivation was not based upon stress per se as exposure to temperature extremes in recooling/rewarming failed to alleviate amnesia. In the present paradigm memory retrieval appears importantly linked to temperature-related contextual cues.