Cortical afferents to the extended amygdala.

The projections of the cerebral cortex to the extended amygdala were studied in the rat using anterograde and retrograde tract-tracing techniques. Most cortical areas with strong projections to the extended amygdala preferentially targeted either the medial extended amygdala (including the medial amygdalar nucleus, ventromedial substantia innominata, and the medial part of the bed nucleus the stria terminalis) or the central extended amygdala (including the central amygdalar nucleus, dorsolateral substantia innominata, and the lateral part of the bed nucleus of the stria terminalis). Some cortical areas, however, had equal projections to both medial and central portions. The main areas projecting preferentially to the medial extended amygdala were the ventral subiculum, infralimbic cortex, ventral agranular insular area, and the rostral part of the ventrolateral entorhinal area. The main areas projecting preferentially to the central extended amygdala were the prefrontal cortex, viscerosensory and somatosensory portions of the insular cortex, and the amygdalopiriform transitional area. It is suggested that these cortical inputs may be important for cognitive, mnemonic, and affective aspects of emotional and motivated behavior.