Early stress and waiting to respond versus waiting to receive.

Chronic social stress in early puberty results in enhanced impulsive action-in particular, decreased action inhibition. We address possible effects of early stress on the capacity to wait to respond, the other form of impulsive action. Male golden hamsters were exposed daily to aggressive adults from postnatal Day 28 to Day 42. Later in adulthood, animals were trained in a variable delay to respond task to nose-poke into a lit opening that triggered the delivery of food pellet rewards in response to a house light. During testing, we introduced random and varying delays between the house light presentation and illumination in the openings and examined premature nose-poking responses as an indicator of impulsive action. As delays grew longer, animals performed more premature responses. However, previously stressed animals were 25% less likely to perform such actions by the longest delay. As a control for this experiment, we conducted a separate study in which we introduced varying delays between the nose-poking response in the lit openings and the delivery of the reward. In this case, there were no significant differences between groups in repeated nose-poking after a correct response (repetitive responses). In summary, early stress has differential effects in response to introduction of delays in conditioning procedures: enhanced tolerance to delays between conditioning cues but no effect on responses when rewards are delayed. These studies confirm that early stress impacts the maturation of the neural systems mediating impulsive responses and provide a new perspective on the neuropsychology of waiting. (PsycINFO Database Record (c) 2020 APA, all rights reserved).