Odor memory after transection of the posterior lateral olfactory tract in the rat

Before surgery rats were trained on a 2-odor discrimination task and tested for acquisition of novel 2-odor discriminations using a 30 s and 10 min intertrial interval. They were retested on a similar series of tasks and on a reversal task after unilateral olfactory bulbectomy (controls) or unilateral bulbectomy plus transection of the contralateral lateral olfactory tract (experimental group). All rats showed rapid acquisition of the 2 odor discriminations both pre- and postoperatively when a short intertrial interval was used. However, in contrast to controls, experimental rats failed to learn the 2-odor discrimination when the intertrial interval was 10 min. When tested on a reversal task, controls showed memory for original learning by making many preseverate errors. Experimental rats quickly acquired the reversal task. These results suggest that lateral olfactory tract afferents to the entorhinal cortex and the projection of the entorhinal cortex to the hippocampus may play a significant role in some aspect of short term memory for odors.