Journal of Cognitive Neuroscience
Addicts and drug-experienced animals have decision-making deficits in delayed reinforcement choice task, in which they prefer small immediate rewards over large delayed rewards. Here, we show evidence that this deficit is accompanied by changed coding of delay length in the basolateral amygdala (BLA). A subset of neurons in BLA demonstrated delay-dependent anticipatory activity (either increase or decrease as a function of delay to reward) in naive rats. After 30 days of withdrawal from chronic cocaine treatment (30 mg/kg/day for 10 days ip), the proportion of delay-dependent anticipatory neurons reduced, whereas delay-dependent activity in response to elapsed delay after reward delivery increased, both in the proportion of delay-dependent neurons and in the extent of delay dependence. Cocaine exposure increased, instead of decreased, BLA neuronal expectation for different reward magnitudes. These results indicate that BLA is critical for representing and maintaining the information of delayed reward before its delivery, and cocaine exposure may affect decision-making by impairing perception of delay instead of the ability to assess the differences in reward size.