Neuroanatomic projections related to biting attack elicited from hypothalamus in cats

Electrodes were implanted in hypothalamic sites from which biting attack upon a rat was elicited by electrical stimulation in cats that did not attack rats spontaneously. The neural degeneration resulting from small lesions made through these attack electrodes was studied with the Fink-Heimer and Eager modifications of the Nauta reduced-silver method. The specific parameters of silver impregnation which were most suitable for each brain were determined, and the measures taken to control for degeneration resulting from the electrode track were described. Degeneration was found to ascend through the preoptic area and diagonal band of Broca into the septum and to descend into the midbrain reticular formation along the course of the medial forebrain bundle and into the central gray substance through the descending periventricular system. Degeneration was also traced into the dorsal hypothalamic area and the midline thalamus. After a lesion of a site adjacent to the ventromedial nucleus of the hypothalamus in one cat from which only escape, but not attack, could be elicited, degeneration was observed in the ventromedial nucleus and in the diagonal band-septal region. The areas to which degeneration was traced were found to coincide well with sites from which attack has been reported to occur during electrical stimulation. The possible significance of the fact that the areas associated with attack behavior are of ancient phyletic origin was discussed.