PubMed Health⌕ Search

Biomedical subjects

I Bodis-Wollner

Publications and source records attributed to I Bodis-Wollner.

At least 37 records · Page 2Linked to original sources
PubMed1997

Electrophysiological evidence for visuocognitive dysfunction in younger non Caucasian patients with Parkinson's disease.

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 "odd-ball" 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 4cpd 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 4cpd 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.

Adult↗
PubMed1997

Visual electrophysiology in Parkinson's disease: PERG, VEP and visual P300.

A retinal dopaminergic deficiency underlies some visual changes in Parkinson's disease (PD), in particular those elicited by stimuli near the peak of the human and monkey spatial contrast sensitivity. The correspondence of retinal changes and VEP alterations is not perfect: they do not seem to rely on identical mechanisms. It seems that additional pathology beyond the retina affects visual responses, including VEPs. The relevance of "distal" primary VEP changes to higher cognitive visual abnormalities in PD is not established at present.

Animals↗
PubMed1997

Functional MRI mapping of occipital and frontal cortical activity during voluntary and imagined saccades.

We investigated the activation of frontal and occipital cortical areas in 14 normal volunteers during voluntary saccades in light or dark and during imagined saccades using functional magnetic resonance imaging (FMRI) with electro-oculogram monitoring. Voluntary saccades in light or dark and imagined saccades led to a significant activation (p < 0.005) of the precentral and posterior medial frontal gyrus (frontal eye field). The medial part of the superior frontal gyrus (supplementary eye field) also showed significant activity during voluntary saccades in all subjects, but only in four subjects during imagined saccades. In addition to frontal activity we found an activated primary visual cortex during voluntary saccades, both in light and in dark. In contrast to executed saccades, imagined eye movements revealed to occipital response under either condition. Our FMRI study supports the concept of frontal eye fields during voluntary saccades and demonstrates that occipital areas are associated with the generation of voluntary eye movements. However, the primary visual cortex is not active when eye movement is only imagined.

Adult↗
PubMed1997

Hidden visual loss in optic neuropathy is revealed using Gabor patch contrast perimetry.

Visual sensitivity was evaluated in the central 16 degrees of the visual field in normal subjects, in patients with glaucomatous optic neuropathy, in glaucoma suspects, and in eyes of patients with multiple sclerosis without evidence of active optic neuritis. A novel method was used to assess sensitivity called contrast perimetry (CP). CP essentially samples every point in the central 16 degrees field, and the normal and deviant responses are relatable to spatial summation of contrast signals. In each visual field quadrant 1 cycles/degree sinusoidal grating stimuli limited in area by a gaussian circular aperture (called a Gabor stimulus) were presented. Contrast sensitivity was measured as a function of stimulus size. The normal curve is nearly S-shaped: For small Gabors contrast sensitivity increases slowly, then accelerates and then flattens again. Patients' results fell into two broad categories: a loss more or only evident for small Gabors and another type of loss for both small and large Gabor size. Glaucoma suspect and most glaucoma eyes showed predominant losses to small Gabors. There were more eyes and more VF quadrants identified by contrast perimetry as abnormal compared to the diagnostic yield of the Humphrey 30-2 (central) visual field even though a Humphrey VF defect was defined liberally. Apparently, contrast perimetry may yield diagnostically useful information of paracentral visual sensitivity. Furthermore, the results suggest that selective losses in POAG and some glaucoma suspects occur to spatially broad-band retinal mechanisms, presumably ganglion cells.

Adult↗
PubMed1996

Simultaneously evoked primary and cognitive visual evoked potentials distinguish younger and older patients with Parkinson's disease.

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 nondemented 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.

Aged↗
PubMed1996

The pattern electroretinogram in Parkinson's disease reveals lack of retinal spatial tuning.

Spatio-temporal visual abnormalities, involving processing of medium coarse stimuli, are known to occur in Parkinson's disease (PD). While these deficits have been related to retinal dopaminergic deficiency, previous ERG studies in PD patients have provided conflicting results, probably due to differences in stimulus conditions. The influence of pattern element size (spatial frequency, SF) on the pattern electroretinogram (PERG) in PD has not been systematically studied. We recorded steady-state PERG to sinusoidal gratings of 50% contrast, counterphase modulated at 7.5 Hz with a series of SFs ranging from 0.5 to 6.9 c/deg in 20 PD patients and 20 healthy volunteers, subdivided in 10 "young" and 10 "age-matched" (AM) subjects. The PERG was analyzed by means of Fast Fourier Transform and the amplitude and the phase of the second harmonic response (15 Hz) were taken into account. We evaluated the medium-to-low SF amplitude ratio and termed it "PERG tuning ratio" (TR). The results indicate that aging affects all the studied SF, but the pattern of age-related loss differs from that observed in PD. Compared to AM subjects, PD patients show a specific deficit at medium SF, with a distorted PERG SF response function. Consequently, all PD patients show an attenuated PERG TR and 17 of them (85%) have an inverted TR. A significant TR decrease is correlated with the clinical stage of PD. There is a marked TR difference between patients receiving and not receiving L-DOPA. We conclude that stimulus SF is a crucial variable of the PERG in PD. PERG measurements and the derived PERG TR may provide a simple tool to evaluate retinal dopaminergic mechanisms and could contribute to the clinical assessment and monitoring of dopaminergic therapy in PD.

Aged↗
PubMed1996

Longitudinal study of a heteroplasmic 3460 Leber hereditary optic neuropathy family by multiplexed primer-extension analysis and nucleotide sequencing.

Nucleotide-sequencing and multiplexed primer-extension assays have been used to quantitate the mutant-allele frequency in 14 maternal relatives, spanning three generations, from a family that is heteroplasmic for the primary Leber hereditary optic neuropathy (LHON) mutation at nucleotide 3460 of the mitochondrial genome. There was excellent agreement between the values that were obtained with the two different methods. The longitudinal study shows that the mutant-allele frequency was constant within individual family members over a sampling period of 3.5 years. Second, although there was an overall increase in the mutant-allele frequency in successive generations, segregation in the direction of the mutant allele was not invariant, and there was one instance in which there was a significant decrease in the frequency from parent to offspring. From these two sets of results, and from previous studies of heteroplasmic LHON families, we conclude that there is no evidence for a marked selective pressure that determines the replication, segregation, or transmission of primary LHON mutations to white blood cells and platelets. Instead, the mtDNA molecules are most likely to replicate and segregate under conditions of random drift at the cellular level. Finally, the pattern of transmission in this maternal lineage is compatible with a developmental bottleneck model in which the number of mitochondrial units of segregation in the female germ line is relatively small in relation to the number of mtDNA molecules within a cell. However, this is not an invariant pattern for humans, and simple models of mitochondrial gene transmission are inappropriate at the present time.

Alleles↗
PubMed1995

Modality dependent changes in event-related potentials correlate with specific cognitive functions in nondemented patients with Parkinson's disease.

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 70 dB 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.

Cognition↗
PubMed1995

On the functional significance of primate retinal dopamine receptors.

Diverse dopamine receptors have been identified in the primate retina. Evidence summarized from human and monkey retinal electrophysiological studies (ERG) suggests that separate D1 and D2 receptor activation results in stimulus dependent antagonistic effects. Studies were performed using Haloperidol, 1-sulpiride, CY 208-243 and dopamine. It is inferred that the antagonistic functions of D1 and D2 receptors synergistically determine the inverted U-shaped spatial contrast response function of the primate retina. An understanding of the logic performed by retinal D1 and D2 receptors may be useful to discern properties of the role of diverse dopamine receptors in basal ganglia DA circuits.

Animals↗
PubMed1994

Visual discrimination and P300 are affected in parallel by cholinergic agents in the behaving monkey.

We studied the acute effect of cholinergic agents, scopolamine alone and scopolamine pretreatment and acetyl-L-carnitine (ALC) on visual event-related potentials (ERPs) in a monkey performing in a go/no-go visual oddball discrimination task. The same monkey was studied repeatedly for a period extending over 1.5 years. Scopolamine is known to cause cognitive impairment in primates. In the concentrations used, primary evoked potentials did not change significantly whereas P300 latency increased maximally 20-40 min following scopolamine administration. Acetyl-L-carnitine on its own increased P300 amplitude and decreased its latency. When ALC administration was preceded by scopolamine, both P300 latency and amplitude maximally increased in 25-45 min. Apparently ALC's effect on the latency and amplitude of visual P300 of the monkey is largely via muscarinic mechanisms. Our results suggest that scopolamine may provide a valuable tool to separate cognitive from primary visual processes.

Acetylcarnitine↗
PubMed1994

Spatial frequency tuning of the monkey pattern ERG depends on D2 receptor-linked action of dopamine.

The pattern electroretinogram (PERG) has been previously shown to be sensitive to dopaminergic manipulations in the monkey's retina. In order to study the role of retinal D2 receptors were recorded the PERG before and during the acute administration of l-sulpiride, a selective D2 blocker, in three monkeys. The stimuli were sinusoidal vertical gratings, with a contrast of 70% counterphase modulated at 7.5 Hz. The response to four different spatial frequencies (0.5, 1.1, 2.3 and 4.6 c/deg) was explored. PERGs were recorded before and after 20 min of i.m. administration of l-sulpiride. Two different doses (0.07 and 0.35 mg/kg) were administered in different sessions for each spatial frequency (SF). Baseline (before sulpiride) responses showed high intersession reproducibility, with a clear SF tuning. Both doses of the drug affected the PERG to the peak SF of the stimulus, but the higher one was more consistently effective in all of the three monkeys. Our results confirm previous studies which suggested that DA is involved in retinal processing in the primate and reveal the new information that D2 receptors are necessary for spatio-temporal tuning of pattern vision.

Animals↗
PubMed1993

The effect of levo-acetyl-carnitine on visual cognitive evoked potentials in the behaving monkey.

We studied acute and chronic effects of levo-acetyl-carnitine (LAC) on event-related potentials (ERPs) in 3 monkeys trained in a "go"/"no-go" visual "oddball" discrimination task. The stimuli were 2.5 cpd sinusoidal gratings differing in their respective orientation only (0 degrees or 45 degrees). Each monkey was trained to release a lever during a prespecified time window. Target stimulus presentation probabilities were between 0.25 and 0.5. ERPs had comparable mean latencies and amplitudes in all monkeys. Primary evoked potentials recorded to either the target or non-target stimulus did not change significantly as a result of LAC treatment. On the other hand, P300 latency decreased following LAC administration, with a maximum occurring in 15-20 min. The major effects of LAC were consistent within each animal and for all three of them.

Acetylcarnitine↗