A pre-clinical study showing how dopaminergic drugs administered during pre-exposure can impair or facilitate latent inhibition.

rationaleIt has been suggested that, in classical conditioning, dopamine (DA) codes for (a) attention to the conditioned stimulus (CS) or (b) the intensity of the unconditioned stimulus.

objectivesTo clarify the role of DA in pre-clinical classical conditioning studies.

methodsAn existing model of classical conditioning presented by Schmajuk, Lam, and Gray (J Exp Psychol Anim Behav Process 22:321-349, 1996) suggests that DA cells in the ventral midbrain area code for the attentionally modulated internal representation of the CS. It is assumed that this representation is increased by dopaminergic agonists and decreased by dopaminergic antagonists. Computer simulations with the model describe the effect of nicotine and haloperidol on latent inhibition.

resultsSimulations replicate experimental results demonstrating that both nicotine and haloperidol affect latent inhibition when administered during the pre-exposure phase. In addition, the model reproduces data showing that administration of nicotine or haloperidol results in the impairment or facilitation of latent inhibition depending on the duration of CS or the number of CSs.

conclusionsThe model demonstrates that pre-clinical experimental results, including cell activity and pharmacological data, are consistent with an attentional role for DA in classical conditioning.