Efferent projections of the anterior olfactory nucleus.

Abstract

AbstractThe efferent projection fibers from the rostral and the medial segments of the anterior olfactory nucleus have been studied using the Nauta or the Fink modification of the Nauta method for degenrating axons. Lesions were suitably placed by electrocoagulation. From the rostral segment of the anterior olfactory nucleus efferent fibers by way of the bulbar part of the anterior commissure were traced to the internal granular and the mitral cell layer of the normal side. Preterminal and terminal degeneration were traced by way of the homolateral lateral olfactory tract and these fibers ended in the lateral two‐thirds of the olfactory tubercle, the prepiriform, the piriform and the periamygdalar cortices and into the corticomedial segment of the amygdaloid complex. Degenerating fibers were also noted in the dorsomedial nucleus, the lateral habenular nucleus, the lateral hypothalamic area and in the supraoptic area of the same side where the lesion was made. In animals where the lesion was placed in the medial segment of the anterior olfactory nucleus the same fiber distribution was observed as reported when the lesion was placed in the rostral segment of the anterior olfactory nucleus. However, other areas were observed receiving fibers from the medial segment of the nucleus. These areas were the basolateral segment of the amygdaloid complex and the mammillary areas.