Role of the hippocampo-septal system, thalamus, and hypothalamus in avoidance conditioning.

Abstract

Rats previously trained to make an avoidance response to the onset of a photic stimulus showed no retention of the habit following bilateral damage to either the septofornix area, hippocampus, anterior thalamus, or posterolateral hypothalamus. Destruction of the anterior hypo-thalamic nuclei or interruption of the rostral medial forebrain bundles did not seriously impair retention. These results point to the priority of a thalamic route over a hypothalamic route in the functional activation of the hippocampo-septal system. A model illustrating critical subcor-tical pathways mediating an avoidance response to light is presented.