Winocur Gordon, Hasher Lynn
Department of Psychology, Trent University, Peterborough, Ont., Canada.
Neurobiol Aging. 2004 Sep;25(8):1107-15. doi: 10.1016/j.neurobiolaging.2003.10.005.
This study provides further evidence that the time-of-day (TOD) when testing is conducted affects cognitive performance in old rats and, for the first time in an animal model, in young adult rats as well. Groups of young and old rats were entrained to a 12-h light-dark schedule and administered tests of learning and memory in a non-matching-to-sample (NMTS) task in a water maze. Testing was conducted at the beginning of the rats' activity cycle (AM) or at the end of the cycle (PM). In addition to age differences in performing the task, there were major findings with respect to time of testing: (1) young rats tested in the PM were better than young rats tested in the AM at learning the NMTS rule and in the delayed-NMTS (DNMTS) task; (2) old rats tested in the AM were better than PM-tested old rats on the DNMTS task, with the former attaining performance levels that approximated those of young rats; (3) the TOD effect in old rats extended to a DNMTS reversal (DNMTS-R) condition in which rats, originally tested in the AM, subsequently were administered the test in the PM, and vice versa; (4) the TOD effects in young and old rats in the DNMTS and DNMTS-R tests were strongest at relatively long delays, suggesting that hippocampal function may be particularly vulnerable to such effects; (5) there was evidence in the old rats of a relationship between diurnal drinking patterns and performance at the longest delay in the DNMTS test. These results, which parallel similar findings with human subjects, emphasize a linkage between circadian rhythmicity and cognitive performance throughout adulthood, and indicate the importance of circadian disruption in old age as a contributing factor to age differences in learning and memory performance.
本研究进一步证明，进行测试的时间（TOD）会影响老年大鼠的认知表现，并且在动物模型中首次发现，也会影响成年幼鼠的认知表现。将幼年和老年大鼠分组，使其适应12小时明暗循环的时间表，并在水迷宫中通过非匹配样本（NMTS）任务进行学习和记忆测试。测试在大鼠活动周期开始时（上午）或周期结束时（下午）进行。除了在执行任务方面存在年龄差异外，关于测试时间还有以下主要发现：（1）在下午进行测试的幼鼠在学习NMTS规则和延迟非匹配样本（DNMTS）任务方面比在上午进行测试的幼鼠更好；（2）在上午进行测试的老年大鼠在DNMTS任务上比在下午进行测试的老年大鼠更好，前者达到了接近幼鼠的表现水平；（3）老年大鼠的TOD效应扩展到DNMTS反转（DNMTS-R）条件，即原本在上午进行测试的大鼠随后在下午进行测试，反之亦然；（4）在DNMTS和DNMTS-R测试中，幼年和老年大鼠的TOD效应在相对较长的延迟时最强，这表明海马体功能可能特别容易受到这种效应的影响；（5）在老年大鼠中，有证据表明昼夜饮水模式与DNMTS测试中最长延迟时的表现之间存在关联。这些与人类受试者的类似发现相平行的结果，强调了昼夜节律与整个成年期认知表现之间的联系，并表明老年期昼夜节律紊乱作为学习和记忆表现年龄差异的一个促成因素的重要性。
