The organization of intraamygdaloid connections; an HRP study.

The localization of neurons from which the projections to other amygdaloid nuclei arise was studied using the retrograde transport of horseradish peroxidase. It was found that the basal nuclei (dorsal and ventral) appear to be the main source of intraamygdaloid connections; they project to the central, medial and lateral nucleus of the amygdala. The medial and the central nucleus receive the most intraamygdaloid connections: the medial--from the basal dorsal, basal ventral, posterior part of the cortical nucleus and from the nucleus of the lateral olfactory tract; the central nucleus--from the basal (dorsal and ventral) nuclei and from the nucleus of the lateral olfactory tract. The afferent intraamygdaloid connections of the cortical and lateral nucleus were also found. These results are discussed with reference to the physiological differentiation and hypothalamic afferents of the amygdaloid body.