Are cross-species measures of sensorimotor gating useful for the discovery of procognitive cotreatments for schizophrenia?

Prepulse inhibition of startle (PPI), a measure of sensorimotor gating used to identify antipsychotics, is reduced in schizophrenia patients and in rodents treated with dopamine agonists or glutamate antagonists. The National Institute of Mental Health (NIMH)-funded Measurement And Treatment Research to Improve Cognition in Schizophrenia (MATRICS) program has initiated a new era in the development of procognitive cotreatments in schizophrenia, independently of treating positive symptoms. Although PPI is not a cognitive process per se, such abnormalities in attention may be predictive of or lead to cognitive deficits. Since first-generation antipsychotics block PPI deficits induced by dopamine agonists, this model cannot identify cognitive enhancers for use as cotreatments with antipsychotics. PPI deficits caused by glutamate antagonists, like the exacerbation of symptoms they produce in patients, are insensitive to dopamine antagonists, but reduced by clozapine. Similarly, both PPI and cognitive deficits in schizophrenia patients are insensitive to first-generation antipsychotics, but attenuated by clozapine. Hence, treatment-induced reversals of glutamate antagonist effects on PPI may provide animal and human models to identify treatments of cognitive deficits in patients already treated with existing antipsychotics.