Temporal neocortical afferent connections to the amygdala in the rhesus monkey.

The temporal neocortical afferent connections to the amygdala were investigated in the rhesus monkey using the silver impregnation and autoradiographic tracing methods. A large topographically organized projection to the amygdala was found to originate from the anterior superior temporal gyrus (area TA), the anterior middle and inferior temporal gyri (area TE), and the medial and lateral aspects of the temporal pole (area TG). These projections terminate in discrete adjacent regions of the lateral and basal amygdaloid nuclei. The temporal pole projection terminates in the ventral two thirds of the medial one half of the lateral nucleus and in the accessory basal nucleus, the anterior superior temporal gyrus projection terminates in the ventral two thirds of the lateral one half of the lateral nucleus, and the anterior middle and inferior temporal gyri projection terminates in the dorsal parts of the lateral and lateral basal nuclei. A projection from the perirhinal cortex to the medial basal nucleus of the amygdala is also discussed. Our findings reveal that a far greater proportion of the temporal neocortex than previously described contributes afferents to the amygdala, further strengthening the view that the amygdala occupies a key anatomical position linking the neocortex with diencephalic structures.