Simultaneously evoked primary and cognitive visual evoked potentials distinguish younger and older patients with Parkinson's disease |
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Authors: | A. Antal R. Pfeiffer I. Bodis-Wollner |
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Affiliation: | (1) Department of Physiology, Albert Szent-Gyorgyi Medical University, Szeged, Hungary;(2) Department of Internal Medicine, Division of Neurology, University of Nebraska Medical Center, Omaha, NE;(3) Present address: Department of Neurology, SUNY, Health Science Center at Brooklyn, Brooklyn, NY;(4) Department of Neurology, University of Tennessee Memphis, Memphis, TN, USA |
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Abstract: | Summary While it is known that both primary visual processes and visuocognitive responses are affected in Parkinson's Disease (PD), their relationship is not known. It is known that both of these measures can be affected by age per se. Our aims were to determine if in non-demented PD patients visual cognitive event-related potential (ERP) changes simply reflect abnormal primary visual processing and to determine the effects of age and disease on their relationship. In order to do so, we introduce a new normalizing procedure for visual ERPs. In addition to the latencies and amplitudes of P100, N140, P200, N200 and P300 components, the P300-P100 latency difference (termed central processing time —CPT) were measured. In order to avoid confounding factors of absolute amplitude differences due to say, generally low voltage recordings or poor primary visual responses, P300 responses normalized to P100 responses were also evaluated (P300/P100 amplitude ratio). Visual ERPs were obtained in an oddball paradigm in 20 non-demented patients with PD and 20 normal age-matched subjects. The stimuli were horizontal sinusoidal gratings differing only in spatial frequency (0.5 and 1 cycle/degree). While simple ERP latency criteria did not distinguish non-demented PD patients as a group from controls, when younger PD patients were compared to older PD patients and controls CPT acceleratedly increased in younger PD patients. The amplitudes of both N200 and P300 provided significant distinction between patient and control groups. The surprising result emerging from this study is that an individually normalized P300 amplitude provides significant distinction of younger PD patients from age matched normals. |
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Keywords: | Parkinson's disease cognition age vision electrophysiology visual discrimination P100 P300 central processing time normalized ERP |
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