4月4日的《科学》（Science）杂志报道说，尽管大鼠可以记住它们发现一片奶酪后已经过了多久的时间，但它们并不真正地形成该发现发生时的有关记忆。以前的研究表明，大鼠与丛鸦似乎记得储存或发现不同食物的事件，但人们仍不清楚的是，这些动物是否真的记住这些事件发生的时间或能感受到自事件发生后已经过去了多少时间。

      William Roberts及其同事设计了一个实验。在该实验中，大鼠在一天中的不同时间去过一个迷宫中的不同分部。迷宫的某些分部中含有中等可口程度的食物小粒，而在某一分部中则放有一片非常可口的奶酪。这些大鼠后来又重新回到该迷宫中，但那片奶酪或被移走或被代之以其他东西。其中一组的大鼠通过记住它们最后遇到奶酪的时间而能够预期那片奶酪是否会在，而另外一组大鼠则与自最后一次遇到奶酪后究竟有多长时间已经逝去保持着追踪联系。那组能够对究竟有多长时间已经逝去保持追踪联系的大鼠的表现要比另外一组要好得多。这表明，和人类不同，大鼠的短暂记忆并不包括记住过去某个事件发生的时间点。

（Science），Vol. 320. no. 5872, pp. 113 - 115，William A. Roberts，Evanya Musolino

Episodic-Like Memory in Rats: Is It Based on When or How Long Ago?

William A. Roberts,^1* Miranda C. Feeney,¹ Krista MacPherson,¹ Mark Petter,² Neil McMillan,¹ Evanya Musolino¹

      Recent experiments with rats suggest that they show episodic-like or what-where-when memory for a preferred food found on a radial maze. Although memory for when a salient event occurred suggests that rats can mentally travel in time to a moment in the past, an alternative possibility is that they remember how long ago the food was found. Three groups of rats were tested for memory of previously encountered food. The different groups could use only the cues of when, how long ago, or when + how long ago. Only the cue of how long ago food was encountered was used successfully. These results suggest that episodic-like memory in rats is qualitatively different from human episodic memory.

¹ Department of Psychology, University of Western Ontario, London, Ontario, N6A 5C2, Canada.
² Department of Psychology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada.