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Claudia Feitosa-Santana, Liana Sanches, Daniel Bertuzzi, Edson Amaro Junior, Dora Ventura; Psychophysical and fMRI Assessment of Magnocellular and Parvocellular Responses in Patients with Parkinson's Disease. Journal of Vision 2018;18(10):34. doi: 10.1167/18.10.34.
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© ARVO (1962-2015); The Authors (2016-present)
Motor effects of Parkinson's disease (PD) are well known but visual aspects are seldom studied. Psychophysical measures of magnocellular (M) and parvocellular (P) visual pathways have shown losses in PD patients (Silva et al., 2005). The objective of this study was: (1) the psychophysical evaluation of luminance contrast discrimination in patients with PD (n=28; mean= 50 ± 9 years old) and age-matched controls using stimuli designed to be selective for M and P pathways in two computerized tests: Pedestal Test (Pokorny & Smith, 1997; Gualtieri et al., 2006) and Checkerboard Test (Benoff et al., 2001; Costa, 2011); (2) the comparison of PD subgroups: early-onset PD (EOPD) (onset before 45 years old; n= 19, mean= 46 ± 6 years old), and non-EOPD (onset after 45 years old and before 65 years old; n= 9; mean= 58 ± 6 years old); and (3) the fMRI assessment with an adapted version of the Checkerboard Test for PD patients (n= 14; mean= 52 ± 10 years old) and age-matched controls. The results indicated: (1) the Pedestal and Checkerboard Tests show that losses occur in both M- and P-pathways in PD-patients; (2) the comparison of the performance of the PD-subgroups with the controls suggests that the M- and P-pathways were impaired in both non-EOPD (Pedestal Test) and EOPD (Checkerboard Test). In addition, this is the first study to suggest that impairments of the M- and P-pathways in non-EOPD are greater than in EOPD (inferred by Pedestal Test); and (3) fMRI responses showed no differences for M- and P-pathways selective stimuli across groups. ROI analysis for V5 and V4 also showed no difference for either P- or M-pathway. These results indicate possible dissociation between the fMRI measures and the psychophysical measures. Future studies with larger samples and/or samples from other populations are necessary. .
Meeting abstract presented at VSS 2018
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