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I Schechter, PD Butler, N Revheim, AM Saperstein, G Silipo, VM Zemon, DC Javitt; M-Pathway Deficits in Schizophrenia: VEPS, Contrast Sensitivity and Functional Outcome . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1810.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Patients with schizophrenia demonstrate deficits of visual processing. We investigated Magnocellular (M) and Parvocellular (P) function using transient and steady-state VEPs (tVEPs and ssVEPs) in addition to contrast sensitivity testing. We then examined the relationship of M and P function and functional outcome. Methods: tVEPs were elicited by checkerboards contrast-reversed at 1 Hz. Either luminance contrast (4% and 100%) or red/green chromatic contrast (100%) were used. ssVEPs were elicited by arrays of isolated checks modulated sinusoidally at 12 Hz with luminance varied parametrically in 1-s steps. Appearance-disappearance and pedestal contrast conditions were used to emphasize M and P activity, respectively. Contrast sensitivity was measured over a range of spatial frequencies (0.5, 1, 2, 4,7, 11, 21 cycles/degree) and determined by forced choice. All controls and patients with schizophrenia were age-matched. Functional outcome was assessed using the problem-solving factor of the Independent Living Scales (ILS-PB). Results: tVEPs to high and low (100% and 4%) achromatic contrasts were significantly reduced in patients with schizophrenia as compared with controls, whereas tVEPs to chromatic contrast checkerboards were not significantly different. ssVEPs to M-biased low luminance contrast stimuli were preferentially decreased in amplitude, whereas P-biased responses were relatively unaffected. Further, contrast sensitivity of patients with schizophrenia to M-biased low spatial frequency stimuli was depressed as compared with controls but sensitivity to P-biased high spatial frequency stimuli were intact. Significant positive correlations were found between ILS-PB scores and M-biased VEPs (tVEPs of 4% achromatic contrast and ssVEPs to low luminance contrast) but not P-biased VEP conditions. Contrast sensitivity at the lowest spatial frequency (0.5 c/deg) correlated with M-biased tVEPs and ssVEPs, as well as with ILS-PB scores. M-biased tVEPs (4% contrast) and M-biased ssVEPs were also significantly correlated. Conclusion: These results indicate a preferential dysfunction of low level M visual pathway which is related to poor functional outcome in schizophrenia.
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