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I Bodis-Wollner

Publications and source records attributed to I Bodis-Wollner.

At least 19 recordsLinked to original sources
PubMed1992

Evidence for two distinct nonlinear components in the human pattern ERG.

We obtained the electroretinogram (PERG) in three observers to a 4.6 c/deg grating pattern with a sinusoidal luminance profile which was modulated in time simultaneously with two sinusoidal temporal frequencies (f1 and f2), or at a single frequency (either f1 or f2). Input temporal frequency ranged from 2.4 to 7.5 Hz. A pattern modulated in the counterphase mode with a single frequency produces a response containing only even harmonics of that frequency. However, when the pattern is counterphase modulated with both f1 and f2, the PERG contains second order response frequencies corresponding to intermodulation components (sums and differences) between the two fundamental frequencies. Such frequencies do not exist in the stimulus--they can only be generated by nonlinear neural interactions. Our results provide evidence for at least two nonsaturating nonlinear response mechanisms in the human retina.

Adult↗
PubMed1992

Sensory evoked potentials: PERG, VEP, and SEP.

The review summarizes current developments in pattern electroretinography practice and theory: generator sources and clinical applications. This is particularly relevant to neuronal disease of the central nervous system (CNS). Visual evoked potentials (VEPs) are discussed in reference to the evolution and follow up of multiple sclerosis (MS) and in conjunction with magnetic resonance imaging (MRI) demonstrated abnormalities. These reveal that the techniques are complementary. Sensory evoked potentials (SEPs) in conjunction with MRI studies are highlighted as quantitatively comparable in spinal cord disorders.

Central Nervous System Diseases↗
PubMed1991

Acetyl-levo-carnitine protects against MPTP-induced parkinsonism in primates.

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 affinity. 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.

Acetylcarnitine↗
PubMed1991

Evidence for two systems mediating perceived contrast.

We report psychophysical evidence for a categorical dichotomy in the perception of contrast. Observers were required to rate the contrast of sinusoidal gratings (2.3 c/d) with contrast varying over a given range relative to two standards. One standard was designated "high" contrast and the other was designated "low." There was a boundary effect: contrast judgment depended upon whether the tested ranges included 10-15% contrast and discrimination was sharpest at the boundary between 10 and 15% contrast. These results are consistent with the existence of two systems underlying perceived contrast; one primarily sensitive below 10%, and the other primarily sensitive above 15% contrast.

Adult↗
PubMed1990

The auditory P 300 correlates with specific cognitive deficits in Parkinson's disease.

An abnormally prolonged latency of the P 300 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 P 300 and a neuropsychological battery of 11 tasks in 43 PD patients. The quantitative relationship between the individual neuropsychological measures and the P 300 was examined using partial correlation and analysis of covariance techniques which controlled for age, education, and illness duration. The strongest correlations were between P 300 and both short-term memory and visual perception. Global cognitive deficits do not appear to relate to the abnormal P 300 responses in PD: instead, specific aspects of cognitive decline accounted for the electrophysiological abnormalities. An abnormally long or absent P 300 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.

Adult↗
PubMed1990

Visual deficits related to dopamine deficiency in experimental animals and Parkinson's disease patients.

In patients affected by Parkinson's disease, and in the monkey model of this disease, visual defects have been shown using psychophysical and electrophysiological measures of spatial and temporal contrast sensitivity. These studies imply an essential role for dopamine in primate vision. There is electrophysiological and neurochemical evidence to suggest that at least part of the problem is impaired retinal processing caused by systemic dopaminergic deficiency. Some of the deficits that have been demonstrated, consistent with physiological studies, suggest that center-surround interaction of neurons may suffer as a consequence of dopaminergic deficiency. The role of the regulation of retinal dopamine (D1 and D2) receptors in primate vision and of the balance of these receptors in presynaptic dopaminergic deficiency is not yet determined. Using sinusoidal grating stimuli in cognitively loaded tasks may increase understanding of the behavioral consequences of visual deficits seen in dopamine deficiency syndromes.

Animals↗
PubMed1990

Visuospatial orientation in Parkinson's disease.

Visuospatial functioning in patients with Parkinson's disease was investigated using neuropsychological measures of basic visual perception, complex perceptual discrimination, and spatial orientation. Three subgroups of patients were described: (a) those with broadly impaired visuospatial abilities, (b) those with generally intact abilities, and (c) those whose performance on a task of spatial orientation was lower than their performance on a task of complex perceptual discrimination. These subgroup differences were also concordant with three other variables: age, duration of disease, and degree of dementia. It is suggested that decreases in spatial orientation functioning in Parkinson's disease may reflect the speed of progression of this disease.

Adult↗
PubMed1990

Physiological effects of acetyl-levo-carnitine in the central nervous system.

Acetyl-levo-carnitine (ALC) is a neuroactive agent. Some studies demonstrate that it modifies cortical electrophysiological responses in animals and man. Foremost, neuronal synchrony appears to be affected. It is thought that ALC is involved in cholinergic neurotransmission although some of its effects may be more complex. Electrophysiological processes involved in cognition may be influenced by ALC: in particular P300, an event-related potential, can be modified. Recent research data in man and monkeys concerning presumed ALC effects on P300 and cognition are summarized.

Acetylcarnitine↗
PubMed1989

The effect of intraocular 6-hydroxydopamine on retinal processing of primates.

In previous studies, we showed that in the monkey, systemically administered N-methyl, 4-phenyl, 1-2-3-6 tetrahydropyridine (MPTP) produces a chronic parkinsonian syndrome accompanied by spatial frequency-dependent abnormalities in both the pattern electroretinogram and visual evoked potential. We describe the effect of intravitreally administered 6-hydroxydopamine (6-OH-DA) on the pattern electroretinogram and pattern visual evoked potential of 3 aphakic monkeys. Because of the aphake condition, several complexities of intravitreal injection of 6-OH-DA could be avoided. Nevertheless, following 6-OH-DA treatment, both the phase and the amplitude of pattern electroretinogram and pattern visual evoked potential became abnormal. This abnormality was most pronounced for the higher spatial frequencies (2.5 and 3.5 cycles per degree), whereas lower spatial frequencies (0.5 and 1.2 cycles per degree) were less impaired. The effects of systemically administered MPTP on pattern electroretinogram and pattern visual evoked potential are similar to the effects of intravitreal injections of 6-OH-DA, suggesting that a retinal catecholaminergic system plays an important role in pattern vision of primates.

Animals↗
PubMed1989

Electrophysiological evidence for interhemispheric transmission of visual information in man.

1. Electrophysiological evidence is presented of interactions between two stimuli (sinusoidal gratings of equal spatial frequency but different contrast, phase-reversed sinusoidally at different temporal frequencies) located on opposite side of, and within a few degrees from, the vertical meridian. 2. These interactions are revealed by a depression of the cortical visual evoked potential (VEP) evoked by the grating of lower contrast in the presence of the grating of higher contrast. They are similar to, albeit weaker than, those obtained with superimposed asynchronously modulated gratings. 3. The VEP reduction occurs also if the stimuli are presented dichoptically. 4. It does not occur if the gratings are located one above the other either on the same or on opposite sides of the vertical meridian. 5. The strength of the VEP reduction depends on the relative contrast of the two gratings and vanishes for spatial frequencies beyond 4 cycles/deg and temporal frequencies of the high-contrast grating beyond 10 Hz. 6. The results are in agreement with data on visual callosal connections in animals and confirm previous psychophysical findings (Berardi & Fiorentini, 1987) indicating the particular properties of the interhemispheric cross-talk between symmetric regions of the visual field astride the vertical meridian in man.

Brain↗
PubMed1989

Electrophysiological and psychophysical testing of vision in glaucoma.

Electrophysiological testing in patients with early glaucoma and in glaucoma suspects reveals defects of central or foveal vision. Most studies suggest that glaucomatous eyes are best separated from normal eyes by use of stimuli with a spatial frequency below the peak of the human contrast sensitivity curve and a relatively high temporal frequency. The stimulus-dependent abnormalities in glaucoma are generally consistent with contrast sensitivity data The stimulus-dependent visual changes are related to the physiology of parallel processing in the primate retinogeniculate pathway.

Aged↗
PubMed1988

Systemic 1-methyl,4-phenyl,1-2-3-6-tetrahydropyridine (MPTP) administration decreases retinal dopamine content in primates.

Following MPTP administration, 4 Cynomolgus monkeys developed a parkinsonian syndrome, accompanied by specific changes of both pattern visual evoked potential and electroretinogram. Retinal dopamine and dihydroxyphenylacetic acid contents were measured in the 4 MPTP-treated monkeys and in 3 normal monkeys. Dopamine and dihydroxyphenylacetic acid levels were significantly lower in the retinas of the MPTP-treated animals (p less than 0.001), suggesting that dopamine has a specific function in the visual system of primates.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1988

Signs of early damage in glaucomatous monkey eyes: low spatial frequency losses in the pattern ERG and VEP.

Experimental glaucoma was created in one eye of three cynomolgus monkeys by argon laser application to the mid-trabecular meshwork. Simultaneous pattern electroretinograms (PERG) and pattern visual evoked potentials (PVEP) were measured in both control and glaucoma eyes to spatial frequencies of 0.5, 1.25, 2.5, and 3.5 cpd which were counterphase modulated at 6 Hz. The transient flash electroretinogram was also measured. While normal flash electroretinograms were recorded in all eyes both before and after the unilateral production of elevated intraocular pressure (IOP), reductions in PERG and PVEP amplitude were seen in the eyes with glaucoma as early as two weeks following a sustained increase of IOP, despite the absence of cupping of the optic nervehead judged by ophthalmoscopic examination and analysis of photograph by two observers. Optic nervehead abnormalities occurred subsequently. In glaucomatous monkey eyes, the earliest PERG and PVEP changes were most evident with lower spatial frequencies of stimulation. Our data suggest that the optimal stimulus parameters for the detection of early glaucoma are low spatial frequency patterns presented at a rapid rate of temporal modulation.

Animals↗
PubMed1988

Spatial frequency-dependent abnormalities of the pattern electroretinogram and visual evoked potentials in a parkinsonian monkey model.

The pattern visual evoked potential (PVEP) and pattern electroretinogram (PERG) were studied in 5 cynomolgus monkeys before and during the development of a parkinsonian syndrome induced by MPTP. The stimuli were vertical bars of four spatial frequencies (0.5, 1.2, 2.5 and 3.5 cycles/degree (cpd) modulated at temporal rates of 1, 4, 6, and 8 Hz. Following MPTP administration, all monkeys developed parkinsonian signs accompanied by changes in the amplitude and latency of the PVEP and PERG. Sinemet L-dopat carbi olopa administration produced temporary recovery of both PVEP and PERG. Two of the monkeys were followed for a prolonged period: 30-40 days after MPTP, the parkinsonian signs showed partial recovery; the PVEP latency and amplitude to 2.5 and 3.5 cpd stimuli and the latency to 1.2 cpd showed improvement but remained abnormal. The latencies of PERGs were normal, but the amplitudes were significantly reduced when stimuli of 2.5 and 3.5 cpd were used. Both PVEP and PERG to 0.5 cpd stimuli returned to normal. No further modifications were seen in the recordings performed 6 months and 1 year later. This study demonstrates (1) that spatial frequency-dependent electrophysiological abnormalities occur in the MPTP-treated monkey, a result previously found in human Parkinson's disease, and (2) that dopamine has a specific function in neurotransmission in the visual system of primates.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗