THALAMIC AND TEMPORAL CORTEX INPUT TO MEDIAL PREFRONTAL CORTEX IN RHESUS-MONKEYS

To determine the source of thalamic input to the medial aspect of the prefrontal cortex, we injected retrograde tracers (wheat germ agglutin in conjugated to horseradish peroxidase, nuclear yellow, and/or bisben zimide) into seven medial prefrontal sites and anterograde tracers (tr itiated amino acids) into six thalamic sites, in a total of nine rhesu s monkeys. The results indicated that ventral precallosal and subcallo sal areas 14 and 25, and the ventral, subcallosal parr of area 32, all receive projections from the mediodorsal portion of the magnocellular division of the medial dorsal nucleus (MDmc). The dorsal, precallosal part of area 32 receives projections mainly from the dorsal portion o f the parvocellular division of the medial dorsal nucleus (MDpc), whic h also provides some input to area 14. Polar area 10 receives input fr om both MDpc and the densocellular division of the medial dorsal nucle us (MDdc), as does supracallosal area 24. Area 24 receives additional input from the anterior medial nucleus and midline nuclei. All medial prefrontal cortical areas were also found to receive projections from a number of cortical regions within the temporal lobe, such as the tem poral pole, superior temporal gyrus, and parahippocampal gyrus. Areas 24, 25, and 32 receive, in addition, input from the entorhinal cortex. Combining these results with prior anatomical and behavioral data, we conclude that medial temporal areas that are important for object rec ognition memory send information directly both to dorsal medial prefro ntal areas 24 and 32 and to ventral medial prefrontal areas 14 and 25. Only the latter two areas have additional access to this information via projections from the mediodorsal part of MDmc.