Effects of partial versus complete lesions of the amygdala on cross-modal associations in cynomolgus monkeys

Abstract

Aspiration lesions of the amygdala plus subjacent cortex were found earlier to produce a severe impairment in cross-modal (tactual-to-visual) recognition (Murray & Mishkin, 1985). To determine whether more selective lesions would also produce this effect, we trained 8 naive cynomolgus monkeys on a tactual-visual version of delayed nonmatching-to-sample and then injected ibotenic acid bilaterally into either the basolateral (n = 4) or centromedial (n = 4) subdivisions of the amygdala. Neither of the excitotoxic lesions affected performance. In a second experiment, we aspirated the amygdala plus subjacent cortex in similarly trained monkeys. The performance of these animals fell significantly and remained substantially below preoperative levels despite extensive postoperative retraining. The findings suggest that the severe deficit in cross-modal recognition following the aspiration lesion is attributable to complete amygdala damage, damage to the subjacent cortex, or the two in combination.