[Internal inhibition in rats after destruction of amygdaloid complex nuclei]

In experiments on male albino rats bilateral lesions of the basolateral amygdala (BLA) impaired extinction and differentiation of the food-procuring conditioned reflexes where as bilateral corticomedial (CMA) lesions had no effect on them. The BLA damage caused a significant impairment of the aversive stimuli discrimination but had no effect on the extinction of the conditioned avoidance reflex in a shuttle-box. The CMA lesions in both hemispheres led to attenuation of aversive stimuli discrimination and delay of avoidance extinction. The data obtained testify to the BLA dominant role in internal inhibition of the alimentary conditioned reflexes and the CMA dominant role in internal inhibition of avoidance conditioning and furthermore to the importance of BLA in the evaluation of the emotional significance and biological validity of the stimuli (reward or punishment).