Neurophysiological Targets for Cognitive Training in Schizophrenia

Schizophrenia is recognized as one of the leading causes of medical disability worldwide, ranked 9th overall by the World Health Organization, and affects more than 2 million Americans per year. There is considerable evidence to suggest that disability status in schizophrenia relates more directly to cognitive Impairment, involving attention, reasoning, and memory, than to characteristic symptoms of psychosis. Accordingly, the evaluation and advancement of interventions designed to restore cognitive function, generally termed cognitive remediation, is of critical importance to our rehabilitation mission. Recent randomized controlled trials of cognitive remediation in schizophrenia have found moderate gains in cognitive function and improved outcomes in important areas of community living. However, despite these encouraging findings, there remains sparse evidence in support of assumptions that (1) cognitive outcomes represent benefits of training-induced adaptive learning, (2) that training effects are specific to method of intervention, or (3) that change in cognitive test performance occurs through restoration of impaired neural circuitry in schizophrenia. This project will begin to address these issues by examining modality-specific effects of computer-based cognitive training on psychophysiological measures of sensory information processing. Training will be administered using two commercially available computer-based software packages, separately targeting auditory and visually-mediated processes using principles of bottom-up perceptual learning. Two psychophysiological paradigms, mismatch negativity (MMN) and P300 generation, will be administered as tests of early visual and auditory processing. MMN and P300 have been studied extensively in human neuroscience as probes of sensory echoic memory and attention engagement to contextually relevant information. Furthermore, reductions in MMN and P300 generation are reliably observed in schizophrenia, follow the course of a progressive neuropathological process, and correlate with severity of cognitive impairment. The specific aims of this study are to determine: (1) whether training selectively influences bottom-up (MMN) or top-down (P300) information processing, (2) whether training effects are modality (auditory vs. visual) specific, (3) whether baseline MMN and P300 predict, or rate-limit, training progress, and (4) whether pre-post change in cognitive test performance is mediated by neural-level change in MMN and P300 generation. Answers to these questions will provide information needed to structure cognitive training for maximum benefit in schizophrenia.