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C. P. Barbosa, F. Benites, L. P. da Nobrega, R. A. Bressan, A. Paranhos Jr; Evaluation of Magnocellular Pathway Dysfunction in Schizophrenia. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5888.
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Visual processing deficits have been reported for patients with schizophrenia. The study of early-stage visual processing is important because deficits in this system can produce lack of information to the visual cortex which can result in clinical symptoms for patients.The aim of this study was to evaluate the magnocellular dysfunction in schizophrenia by utilizing the frequency doubling technology (FDT).
Twenty DSM- IV schizophrenic patients 29 healthy volunteers were examined. Subjects were excluded if they met criteria for alcohol or substance dependence or had any neurological or ophthalmologic disorder that might affect their performance. FDT testing was performed in one session. First was used the screening strategy and 15 minutes later the C-20 program for FDT. The stimuli have a sinusoidal pattern with frequency of 50 Hz. The subject’s task was simply to press one button if a grating appeared.The analysis of global sensitivity and cerebral hemisphere sensitivity were performed. The MD (mean-deviation) was used for the global sensitivity. The right hemisphere analysis included the mean sensitivity of left temporal and right nasal hemifield.The left hemisphere analysis included the mean sensitivity of right temporal and left nasal hemifield.
Schizophrenia patients showed a lower general sensitivity mean (30,97 dB ± 2,25) in comparison with the control group mean (32,17 dB ± 3,08), but this difference was not statistically significant. Fovea sensitivity was different (-1,61 ± 3,14 dB for patients versus- 0,45 ± 1,77 dB for controls),(p = 0,055; power = 0,48). There was no difference in the delta of hemispheres between patients and controls, although the right hemisphere sensitivity was lower in patients (mean -0,26 ± 1,32 dB) in comparison to control group (mean 0,12 ± 1,02 dB), without statistical significance. There was no association between the positive-negative symptoms and general MD, foveal MD and the difference between the hemispheres (p > 0,05).
These preliminary results suggest that there are small differences between global sensitivity and hemisphere sensitivity measured by FDT. However, a larger sample size is required to evaluate the dysfunction in magnocellular pathways hypothesis.The present findings contribute to a significant body of research to assess early-stage visual processing deficits for patients with schizophrenia.
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