A simple and reliable test of olfactory learning and memory in mice

The present paper describes a quick and efficient method for assessing olfa ctory discrimination learning in mice. In training mice received trials in which one odor (CS+) was paired with sugar and another odor (CS-) was paire d with no sugar. When the mice were subsequently placed in a chamber with C S+ odor at one end and CS- odor at the other, they spent more time digging in CS+ than in CS- odor. In Experiment 2 mice trained with this procedure a nd tested after 60 days also spent more time digging in CS+ than CS- in the test phase, indicating that this olfactory discrimination task is effectiv e for assessing long-term memory. In addition to the outbred strain of CD1 mice used in Experiments 1 and 2, C57BI/6NCr/BR and DBA/2NCr/BR mice used i n Experiment 3 also acquired this learned odor discrimination. Moreover, Ex periment 4 showed that DBA animals were capable of acquiring this odor disc rimination after receiving only two training trials (one exposure each to C S+ and CS-) per day for 4 days.