Subcortical structures mediating the attention response induced by amygdala stimulation

It is suggested that the amygdaloid attention response is mediated through several of these subcortical areas which could not be eliminated in toto in one and the same animal, because such extensive lesions were not compatible with survival.

Abstract

Electrical stimulation of the amygdaloid nuclear complex in unanesthetized freely moving cats elicits a characteristic searching or attention response. Attempts have been made by combined stimulation-ablation techniques to determine the subcortical structures through which this response is mediated. The only lesion which eliminated the attention response was an almost complete vertical circumcision of the amygdala with interruption of the connections irradiating in the anteromedial, medial, and posteromedial directions. Selective section of any of these connections by lesions placed either anteromedially, medially, or posteromedially to the amygdala, in various combinations, were ineffective. It is concluded that the attention response is mediated through several pathways to widespread subcortical areas. Bilateral lesions of various subcortical nuclei onto which the amygdala is known to project did not abolish the attention response. Such lesions destroyed in various combinations the almost entire thalamus (including all mid-line and intralaminar nuclei), the subthalamus, extensive parts of the hypothalamus (including nucleus ventromedialis), and the preoptic area, the septal nuclei, the reticular formation, and the rostral half of the periaquaeductal gray matter of the midbrain, the pretectal area, the superior colliculi, the habenula, the substantia nigra, and the red nuclei. It is suggested that the amygdaloid attention response is mediated through several of these subcortical areas which could not be eliminated in toto in one and the same animal, because such extensive lesions were not compatible with survival.