Procedural Learning in Schizophrenia Can Reflect the Pharmacologic Properties of the Antipsychotic Treatments

Background: Conventional and atypical antipsychotics have different affinities for D₂ receptors, and these receptors are principally located in the striatum. Given that this cerebral structure was previously found to play a major role in procedural learning, the antipsychotic treatment in schizophrenia may be determinant for the procedural learning profile of these patients. Objective: The current study was aimed at verifying whether procedural learning differs in patients with schizophrenia treated with conventional antipsychotics and patients treated with atypical antipsychotics. Method: Forty-five patients with schizophrenia were divided into 3 different groups according to their pharmacologic treatment: (1) haloperidol, a classical neuroleptic with high D₂ receptor affinity; (2) clozapine, an atypical neuroleptic with practically no D₂ receptor affinity; and (3) risperidone, an atypical neuroleptic that nevertheless shows high D ₂ receptor affinity. Patients were compared to 35 control subjects on a visuomotor procedural learning task (mirror drawing). Results: All patients were able to learn the task. However, those treated with haloperidol showed some degree of learning impairment, while those treated with clozapine or risperidone did not show this impairment. In addition, performance per se, regardless of the learning, was found to be affected in the haloperidol and risperidone, but not in the clozapine groups. Conclusion: Procedural learning in schizophrenia may be differentially affected, depending on the pharmacologic profiles of the antipsychotics used for the treatment of this illness.