ROLE OF EXPERIENCE IN RECOVERY OF FUNCTION FOLLOWING ORBITAL PREFRONTAL LESIONS IN INFANT MONKEYS

Spatial delayed alternation ability was compared in 2 groups of monkeys [Macaca mulatta] with identical orbital prefrontal cortical lesions given in infancy, but different training histories: one group, initially trained on delayed alternation at 1 yr of age, was retested at 2 yr; the other, first trained at 2 yr, was retested at 3. Both groups exhibited severe impairments upon initial testing but considerable restitution of ability upon retesting, in contrast to monkeys operated upon as juveniles. Such recovery, occurring preferentially in monkeys given orbital prefrontal lesions as infants, depends upon experience and does not occur spontaneously with the passage of time or maturation.