Recovery rate as a determinant of the amnesic-like effect of hypothermia

Abstract

Two experiments were performed to determine the role of depth and duration of hypothermia in hypothermia-produced impairment of the rat's retention of a one-trial passive avoidance task. The first experiment varied depth of hypothermia and held duration constant by varying recovery rate. The results indicated a graded impairment of memory for animals cooled in 5–15°C water. No difference in memory impairment obtained in animals cooled in 0°C and 5°C water. These results suggest that depth of and/or rate of recovery from hypothermia play a significant role in hypothermia-produced amnesia. The second experiment varied duration of hypothermia, holding depth constant. The results indicated that rate of recovery was a prime determinant of hypothermia produced forgetting. Animals whose body temperatures were kept below normal for an extended period of time displayed little or no amnesic-like behavior, whereas animals whose body temperatures were returned to normal at a relatively rapid rate showed extensive forgetting. These results were attributed to retrieval failure rather than to a disruption of memory consolidation.