Schizophrenia is a chronic, severe, mental illness, with over 2.5 million individuals estimated to have this disorder in the United States alone. Schizophrenia has been associated with a large number of neurocognitive deficits that researchers have investigated to better understand the underlying etiology and subtypes. One deficit that has received considerable attention is dysfunction in early visual processing, which has been assessed with visual-evoked potentials (VEPs) using electroencephalography. Most VEP studies have suggested a hypoactive magnocellular (M) visual pathway in individuals with schizophrenia, while a smaller number of studies have suggested that the parvocellular (P) pathway may also be hypoactive. A separate line of investigation has demonstrated that a subset of individuals with schizophrenia show an abnormal change in visual processing to red light. Despite the existing research on these visual processing abnormalities in schizophrenia samples, they remain poorly understood in terms of related symptom profiles and neurobiological etiologies. To address this need, the proposed 3-year project will assess 100 individuals with a broad range of schizophrenia-related disorders and 100 controls. The study will use a comprehensive diagnostic and symptom assessment (both self-reported and clinician administered) along with a VEP task to examine the relationship of the early visual processing abnormalities with clusters of schizophrenia-related symptoms. We expect that the VEP-to-symptom relationships will be stronger when examined across the diagnostic boundaries of the schizophrenia-related disorders rather than within particular diagnoses. VEPs will be elicited using a repeated transient (60 ms) presentation of a checkered pattern (presented at either high or low contrast) on alternating green and red backgrounds. We will examine whether there are specific differential clusters of schizophrenia-related symptoms that relate to VEP abnormalities of interest (which includes the abnormal change to red light). In addition, we will examine how each VEP abnormality relates to visual and auditory working memory performance. The results from this study will have strong potential to increase our understanding the underlying neuropathology and etiology of the schizophrenias that likely underlie our unitary concept of schizophrenia. This could potentially uncover new clinically-meaningful diagnostic categories, thereby facilitating the search for more effective pharmacological interventions for this devastating condition. Early identification of these deficits could also set the stage for intervention or prevention programs to ameliorate the most impairing aspects of this disorder.
Despite numerous studies of early sensory deficits in schizophrenia, there is still only minimal understanding of the underlying brain abnormalities and causes of the disorder, and it is likely that what we now call schizophrenia is actually many different underlying disorders. The proposed study will examine whether there are specific clusters of schizophrenia-related symptoms that relate to specific early visual processing abnormalities. The results from this study will have strong potential to uncover new schizophrenia subtypes, thereby facilitating the search for more effective treatments and prevention programs for this devastating condition.