Cold-induced impairment of delayed matching in rats

Exposure to moderate, nonhypothermic cold temperature has been reported to affect a variety of behavioral and neural functions. To elucidate the effects of mild cold stress on short-term (working) memory, Long-Evans rats were exposed to an ambient temperature of either 2 degrees or 23 degrees C while performing a delayed matching task. At the beginning of each trial, rats were required to respond on one of two levers cued by a light. Following a delay of 2, 8, or 16 s, a response on the lever previously cued produced food reinforcement. Relative to performance at 23 degrees C, exposure to 2 degrees C occasioned no change in matching accuracy at the 2-s delay, a modest decrement at the 8-s delay, and a larger decrement at the 16-s delay. The cold exposure did not decrease colonic temperature. In addition to accuracy decrements, matching response times were consistently shorter during cold exposures. Cold-induced impairments were absent during removal of the memory component from the task, indicating the observed cold effects on memory were not due to impaired attentional, sensory, or motor processes. These data suggest that mild cold stress may impair active maintenance of information in working memory but not processes related to reference memory.