Psychopharmacological approaches to modulating attention in the five-choice serial reaction time task: implications for schizophrenia

Rationale. In schizophrenia, attentional disturbance is a core feature which may not only accompany the disorder, but may precede the onset of psychiatric symptoms. Objectives. The five-choice serial reaction time task (5CSRTT) is a test of visuo-spatial attention that has been used extensively in rats for measuring the effects of systemic and central neurochemical manipulations on various aspects of attentional performance, including selective attention, vigilance and executive control. These findings are relevant to our understanding of the neural systems that may be compromised in patients with schizophrenia. Methods. The 5CSRTT is conducted in an operant chamber that has multiple response locations, in which brief visual stimuli can be presented randomly. Performance is maintained using food reinforcers to criterion levels of accuracy. Various aspects of performance are measured, including attentional accuracy and premature responding, especially under different attentional challenges. Results. The effects of systemic and intra-cerebral infusions of selective dopamine, serotonin and cholinergic receptor agents on the 5CSRTT are reviewed with a view to identifying attention-enhancing effects that may be relevant to the treatment of cognitive deficits in schizophrenia. In addition, some novel agents such as modafinil and histamine receptor agents are also considered. Examining the effects of selective neurochemical lesions helped define the neural locus of attentional effects. Similarly, findings from microdialysis studies helped identify the extracellular changes in neurotransmitters and their metabolites in freely moving rats during performance of the 5CSRTT. Conclusions. The monoaminergic and cholinergic systems have independent but complementary roles in attentional function, as measured by the 5CSRTT. These functions are predominantly under the control of the prefrontal cortex and striatum. These conclusions are considered in the context of their application towards therapeutic approaches for attentional disturbances that are typically observed in schizophrenic patients.