Disruption of selective attention in the rat following chronic d-amphetamine administration: relationship to schizophrenic attention disorder.

In the blocking paradigm, prior training to one conditioned stimulus (CSA) blocks the ability to attend to a second conditioned stimulus (CSB) when the two form a compound (CSAB) in subsequent training. Blocking is an associative process by which animals learn to ignore CSB because it contains no new information regarding the reinforcing event. Experiment 1 showed that d-amphetamine disrupted rats' ability to ignore the irrelevant CSB: The animals responded equally to both elements of the CSAB compound following five dialy administrations of 4 mg/kg d-amphetamine. In Experiment 2 the disruption of blocking by d-amphetamine was eliminated by concomitant administration of 0.02 mg/kg haloperidol. These results are consistent with previous research showing that d-amphetamine disrupts rats' ability to ignore repeated presentations of a single nonreinforced stimulus in the latent inhibition paradigm. The inability of amphetamine-treated animals to ignore one element of a dual-element compound bears some resemblance to selective attention deficits seen among schizophrenic patients.