Fibre Degeneration Following Lesions of the Amygdaloid Complex in the Monkey

Of the amygdaloid projection pathways the stria terminalis has traditionally received strong emphasis in anatomical studies, and less attention has customarily been given other fibre systems originating in the amygdaloid complex. It is, however, known that the amygdala is connected with other basal telencephalic structures and with the diencephalon by a massive ventral fibre system which spreads forward and medially through the region underneath the lentiform nucleus. This fibre system appears to have been recognized first by Johnston (1923), who considered it to be an amygdalofugal component of his 'longitudinal association bundle'. Johnston limited his account of this projection system to the statement that such fibres beneath the globus pallidus join 'the general system of precommissural fibres passing up through the parolfactory area'. Later workers, on the basis of experimental-anatomical observations in the cat, described distributions of the ventral amygdalofugal fibre system to the preoptic region and hypothalamus (Lammers Hall, 1960), the bed nucleus of the stria terminalis (Fox, 1943), the caudate nucleus and the subcallosal gyrus (Lammers & Lohman, 1957).