THE AMYGDALAE AND BEHAVIOR

The individual and social behavior of 15 cats and 18 rhesus monkeys was recorded and analyzed during a control period of from 3 to 15 months, during which the animals were also trained to solve increasingly complicated problems. Adaptational conflicts were used to induce persistent experimental neuroses in 3 kittens, 2 cats, 3 young monkeys and 8 adult ones. The amygdalae were then totally ablated, with some injury to the surrounding areas, in 6 of the cats and all of the monkeys; in the remaining 9 cats only the lateral or the medial amygdalae were removed.

Postoperatively, the cats exhibited: 1. no general amnesia for previous learning; 2. only mild amelioration of neurotic behavior; 3. moderate motor restlessness; 4. variable sexual drive including a phase of hypererotism; 5. markedly altered interactions with other cats and humans; 6. slowed re-learning due to low motivation and erratic or perseverative performance on both simple and complex tasks; and 7. severe disorganization of adaptive behavior after short periods of isolation and inactivity. The adult neurotic animals were: 8. markedly amenable to therapy although the kittens very low resistance to the re-induction of were only mildly so; whereas 9. all showed neuroses.

In comparison, the monkeys showed 1. an initial increase in oral activity; 2. extensive amnesia for previous learning, coupled with 3. limited diminution of neurotic symptoms in the young animals as contrasted with almost complete amelioration in the adults; 4. the ability to regain preoperative performance levels on learned problems, although the retraining period was lengthened by altered motivation, restlessness in the testing apparatus, and precipitate or inflexible responses; 5. tolerance of the proximity of or handling by a single human, contrasted with 6. fear responses to other animals or when more than one human was present; 7. increased inter-animal aggression, possibly related to 8. hypersexuality; and 9. diminished resistance to the re-induction of neuroses.

The theoretical implications of these finding were briefly considered.