Amygdalar connections of the macaque areas 45A and 45B

Marzio Gerbella, Matteo Baccarini, Elena Borra, Stefano Rozzi, Giuseppe Luppino

In the present study, based on injections of retro- or retro-anterograde tracers at the cortical level, we analyzed the amygdalar connections of the caudal ventrolateral prefrontal areas 45A and 45B of the macaque and compared them with those of the adjacent areas 8/FEF, 8r, 46v, and 12r. The results showed that areas 45A and 45B display reciprocal amygdalar connections, which appear to be considerably richer than those of their neighboring areas. Specifically, these two areas are a target of differentially weighted projections originating predominantly from the magnocellular and the intermediate subdivisions of the basal nucleus and are a source of projections mostly directed to the magnocellular subdivision of the basal nucleus and the dorsal part of the lateral nucleus. The present data, together with previous data on the thalamic connectivity of areas 45A and 45B (Contini et al. Eur J Neurosci 32:1337-53, 2010), suggest that direct and indirect-trans-thalamic-amygdalar connectivity is a characterizing connectional feature of these two areas. Specifically, the amygdalar connections of area 45A, for which a role in communication behavior has been proposed, could convey information on the emotional significance of communicative signals to this area, where it could play a crucial role in guiding appropriate social interactions. Furthermore, the amygdalar connections of area 45B, possibly involved in higher-order aspects of visual guidance of gaze, could convey information related to the relevance of visual stimuli, which could contribute to a representation of priority maps in this VLPF area.