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  • 1
    Electronic Resource
    Electronic Resource
    Modality dependent changes in event-related potentials correlate with specific cognitive functions in nondemented patients with Parkinson's disease (1995)
    Springer
    Journal of neural transmission 9 (1995), S. 197-209 
    Details
    ISSN: 1435-1463
    Keywords: Parkinson's disease ; auditory and visual event-related potentials ; P300 ; N200 ; cognition ; visuospatial deficits ; neuropsychological measures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The relationship between event-related potentials (ERPs) and cognitive functioning was studied in patients with Parkinson's Disease (PD) but without dementia. Auditory and visual stimuli were used; 30 subjects participated in the auditory study and 20 in the visual study. Patient groups did not differ with respect to gender, age, education, illness duration, and level of cognitive functioning. Visual stimuli were 2.3 cpd sinusoidal grating patterns randomly presented in an oddball paradigm (oblique vs. vertical spatial orientation). Auditory stimuli were tones presented at 70dB SPL at a rate of 1.1/second, also using the oddball paradigm (1.5K vs. 1K tones). All patients were given neuropsychological tests to measure verbal fluency, memory, visual spatial perception, and abstract reasoning. P300 and N200 abnormalities correlated with a number of these measures, such that longer ERP latencies were related to lower scores on tests of cognitive functioning. Patterns of results suggest that auditory and visual ERPs correlate with different subsets of neuropsychological functions in nondemented PD patients and that N200 may provide a new metric for clinical use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02259661
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  • 2
    Electronic Resource
    Electronic Resource
    The auditory P300 correlates with specific cognitive deficits in Parkinson's disease (1990)
    Springer
    Journal of neural transmission 2 (1990), S. 249-264 
    Details
    ISSN: 1435-1463
    Keywords: Parkinson's disease ; P300 ; evoked potential ; neuropsychological measures ; cognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An abnormally prolonged latency of the P300 event-related potential has been reported in several types of dementing illnesses, including Parkinson's disease (PD). While some PD patients have dementia, a significant number of PD patients have less severe cognitive impairments. We examined the relationship between the auditory P300 and a neuropsychological battery of 11 tasks in 43 PD patients. The quantitative relationship between the individual neuropsychological measures and the P300 was examined using partial correlation and analysis of covariance techniques which controlled for age, education, and illness duration. The strongest correlations were between P300 and both shortterm memory and visual perception. Global cognitive deficits do not appear to relate to the abnormal P300 responses in PD: instead, specific aspects of cognitive decline accounted for the electrophysiological abnormalities. An abnormally long or absent P300 correlated with deficits on select cognitive tasks: those involving memory, visual perception, and abstract reasoning. The interactions between anatomical and neurochemical abnormalities in PD are discussed in light of the pattern of deficits seen in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02252920
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Simultaneously evoked primary and cognitive visual evoked potentials distinguish younger and older patients with Parkinson's disease (1996)
    Springer
    Journal of neural transmission 103 (1996), S. 1053-1067 
    Details
    ISSN: 1435-1463
    Keywords: Parkinson's disease ; cognition ; age ; vision ; electrophysiology ; visual discrimination ; P100 ; P300 ; central processing time ; normalized ERP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01291790
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The hemispheric distribution of the transient rat VEP: a comparison of flash and pattern stimulation (1985)
    Springer
    Experimental brain research 59 (1985), S. 427-433 
    Details
    ISSN: 1432-1106
    Keywords: Hooded rat ; Flash VEP ; Pattern VEP ; Hemispheric lateralization ; Visual fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We investigated the hemispheric distribution of the rat visual evoked potential (VEP) to pattern reversal and flash stimuli, presented monocularly at a rate of 1 Hz. Pattern VEP components could be recorded only over an area bounded by the anatomical coordinates of area 17, while some flash VEP components were recordable outside the primary visual area. Monocular pattern stimulation, as expected, evoked dominant contralateral VEPs. Surprisingly, ipsilateral responses could be also recorded with the reference electrode near the nasal bone. These VEPs showed partial polarity inversion compared to the contralateral EPs. To assess the origin of the ipsilateral EPs, we also recorded EPs following surgical deafferentation of the ipsilateral cortex. Our data reveal that ipsilateral VEPs represent volume conducted potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261332
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of contrast and spatial frequency on the visual evoked potential of the hooded rat (1984)
    Springer
    Experimental brain research 57 (1984), S. 1-8 
    Details
    ISSN: 1432-1106
    Keywords: Hooded rats ; Visual evoked potentials ; Contrast ; Spatial frequency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Transient and steady-state visual evoked potentials, obtained with counterphase modulated grating patterns, were recorded through chronically implanted electrodes in lightly anesthetized and unanesthetized hooded rats. As a function of spatial frequency, the latency of the major positive wave (P1) of the transient VEP was minimal with a 0.1 cycles per degree (cpd) grating as stimulus. The amplitude of the P1-N2 component remained constant from 0.04 to 0.20 cpd and then decreased with higher spatial frequencies. The function relating amplitude of steady-state VEP to spatial frequency at high contrast depended on temporal frequency: It had a band-pass form at 5.0 Hz and a low-pass form at 8.4 Hz. As a function of contrast, the latency of the P1 wave linearly decreased and its amplitude increased with increments of contrast up to 55%. The contrast function of the amplitude of the second harmonic of the steady-state VEP (8.4 Hz) showed two linear segments: one for low contrasts with a shallow slope and one for high contrasts with a steep slope, suggesting two distinct contrast mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231126
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  • 6
    Electronic Resource
    Electronic Resource
    Electrophysiological evidence for visuocognitive dysfunction in younger non caucasian patients with Parkinson's disease (1997)
    Springer
    Journal of neural transmission 104 (1997), S. 427-439 
    Details
    ISSN: 1435-1463
    Keywords: VEP ; visual P300 ; visuo-cognitive decline ; Parkinson's disease ; age effect ; population comparison
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A study of “primary” (VEPs) and “cognitive” (ERPs) visual evoked potentials was carried out in a group of non-demented Afro-American Parkinson's disease (PD) patients. Current studies suggest that differences exist in the clinical manifestations of PD in Caucasian and non-Caucasian populations. Two horizontal sinusoidal gratings differing in spatial frequency, i.e., 1 and 4 cycles per degree (cpd), were presented in an “oddball” paradigm to 17 patients with PD and 17 age-matched control subjects. While the 1 cpd stimulus, is not expected to reveal retinal dopaminergic deficency, but only visuocognitive deficits, the 4 cpd may give direct information of both “retinal” and “cognitive” visual deficits. We measured the latencies and amplitudes of N70, P100 and P300 components, and derived the “normalized” measures of P300-N70 latency difference (Central Processing Time-CPT70), the P300-P100 latency difference (CPT100) and the P300 amplitude responses normalized to either N70 and P100 amplitude (Amplitude Ratios AR70 and AR100). Our results do show that cognitive electrophysiological deficits in younger PD patients exist in non-Caucasians, perhaps to an even greater degree than in Caucasians, and confirm that absolute and normalized ERP amplitude and latency abnormalities are a distinguishing feature of younger PD patients from controls. In particular P300 measures are abnormal for 1 cpd pattern. A negative correlation exists between P300 amplitude and the motor score. By comparing the results for 1 and 4 cpd stimuli it can be concluded that “primary” and “cognitive” visual abnormalities are independently affected in PD, implying that visuo-cognitive abnormalities are not passively determined by retinal dopaminergic deficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01277661
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  • 7
    Electronic Resource
    Electronic Resource
    Acetyl-levo-carnitine protects against MPTP-induced parkinsonism in primates (1991)
    Springer
    Journal of neural transmission 3 (1991), S. 63-72 
    Details
    ISSN: 1435-1463
    Keywords: Acetyl-levo-carnitine (ALC), MPTP ; primate ; parkinsonism ; dopaminergic ; cellular protection ; mitochondrion ; electrophysiology ; histochemistry ; catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Acetyl-levo-carnitine (ALC) protects against 1-methyl, 4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced toxicity in the nonhuman primate. ALC pretreated monkeys do not show signs of parkinsonism or electroretinographic changes typical of dopaminergic deficiency when given MPTP. In addition, pilot neurochemical and morphological data confirm a partial protection effect. While MAO-B inhibitors, like L-Deprenyl, are thought to protect dopaminergic neurons from MPTP-induced cell death by preventing the conversion of MPTP to its toxic metabolite MPP+, ALC is not known to have MAO-B affnity. Converging evidence suggests that ALC may affect directly mitochondrial respiration, which is known to be the target of MPP+ and affected in human neurodegenerative diseases, including Parkinson's disease. The results of this study point to new therapeutic avenues for the treatment of these nosologic entities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02251137
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