Midbrain course of descending pathways mediating sham rage behavior

Abstract

The midbrain course of descending pathways mediating sham rage behavior has been investigated in thalamic cats. Electrical stimulation of the lateral hypothalamus has been tested for rage outbursts before and following various lesions in the midbrain. The following lesions were found not to impair transmission of the descending hypothalamic influences: transection of the rostral third of the central periaqueductal gray and adjacent tegmentum, with interruption of the hypothalamic component of Schütz's dorsal longitudinal fasciculus; midline lesions, including the medial component of the medial forebrain bundle to the ventral tegmental area of Tsai and to the caudal periaqueductal gray; and lateral tegmental lesions involving the lateral component of the medial forebrain bundle to the lateral midbrain tegmentum. Large lesions involving most, though not all, of the tegmentum at the midcollicular level impaired, but did not abolish, rage responses to lateral hypothalamic stimulation. It is concluded that descending connections from the lateral hypothalamus, responsible for the peripheral manifestations of rage, are diffuse through the midbrain, including both the lateral and the medial components of the medial forebrain bundle, and possibly the dorsal longitudinal fasciculus as well.