DIRECT PROJECTIONS FROM THE ENTORHINAL AREA TO THE ANTEROVENTRAL AND LATERODORSAL THALAMIC NUCLEI IN THE RAT

The present study provides the evidence for the existence of direct pr ojections from the entorhinal area to the anteroventral (AV) and later odorsal thalamic nuclei (LD) in the rat. The retrograde tract-tracing method with cholera toxin B subunit and the anterograde tract-tracing method with Phaseolus vulgaris leucoagglutinin were used. The projecti on fibers originate from layers V and VI of the medial entorhinal area and terminate in the rostral and dorsolateral parts of the AV and the dorsal part of the LD. The projections are organized in a coarse topo graphic fashion. The rostral part of the medial entorhinal area projec ts preferentially to the AV whereas the caudal part projects preferent ially to the LD. The results show that the medial entorhinal area is c onnected reciprocally with the AV and LD. Thus, the AV and LD are inti mately connected with the limbic cortex implicated in memory and learn ing.