Preserved stimulus-reward and reversal learning after selective neonatal orbital frontal areas 11/13 or amygdala lesions in monkeys

Neither lesions of orbital frontal (OFC) areas 11/13 nor selective amygdala lesions alter the ability to learn stimulus-reinforcer association and reversal discriminations in adult monkeys. Here, we investigated whether the same conclusion will hold true when the same lesions occur in infancy. Infant rhesus monkeys received sham-operations, neurotoxic amygdala lesions, or aspiration OFC 11/13 lesions at 8–15 days of age and were trained on object discrimination reversal (ODR) tasks. Performance on a single pair (1-Pair) ODR was assessed at the age of 3 months and 3 years, and then animals were tested in a 5-Pair ODR task in which they had to concurrently learn and reverse five discrimination problems. The results indicated that the ability to solve a single-pair discrimination problem followed by six reversals appears to be late maturing in monkeys but is spared following selective lesions of either OFC areas 11/13 or amygdala, even with the use of the more challenging 5-object ODR task. Finally, performance in the 1 and 5-Pair ODR at 3 years was comparable to that following adult-onset lesions, indicating that neither OFC areas 11/13 nor amygdala are critical for the development of reversal learning.

* We examined reversal learning in monkeys at two time points (3 months and 3 years). * Reversal learning follows a protracted development. * The amygdala is not necessary to develop normal reversal learning abilities. * Areas 11/13 of the OFC are not necessary for developing reversal learning abilities.