The effect of background spatial contrast on electroretinographic responses in the human retina

AbstractThe electroretinogram (ERG) was obtained to contrast modulation (CM). This stimulus is a product of temporal modulation of the contrast of a spatial sinusoid at constant mean luminance. Mean contrast (10–40%), and modulation depth (25–1.0) were modulated at 7.5Hz to record the pattern electroretinogram (PERG). The spatial pattern was a foveally fixated grating pattern with sinusoidal luminance profile with spatial frequency of 4.6c/deg. CM resulted in significant first and second harmonic ERG responses. First harmonic amplitude increases then flattens as a function of mean contrast with ΔC=constant, while the second harmonic response remains unaffected by mean contrast. Apparently the first harmonic represents summed signals of local luminance responses arising from on and off neurons. Mean spatial contrast signals modulate preganglionic local luminance responses

Interocular Asymmetry of Foveal Thickness in Parkinson Disease

Purpose. To quantify interocular asymmetry (IA) of foveal thickness in Parkinson disease (PD) versus that of controls. Design. Prospective case-control series. Methods. In vivo assessment of foveal thickness of 46 eyes of 23 PD patients and 36 eyes of 18 control subjects was studied using spectral domain optical coherence tomography (SD-OCT). Inner versus outer layer retinal segmentation and macular volumes were quantified using the manufacturer's software, while foveal thickness was measured using the raw data from each eye in a grid covering a 6 by 6 mm area centered on the foveola in 0.25 mm steps. Thickness data were entered into MATLAB software. Results. Macular volumes differed significantly at the largest (Zone 3) diameter centered on the foveola (ETDRS protocol). By segmenting inner from outer layers, we found that the IA in PD is mostly due to changes on the slope of the foveal pit at the radial distances of 0.5 and 0.75 mm (1.5 mm and 1 mm diameter). Conclusions. About half of the PD patients had IA of the slope of the foveal pit. IA is a potentially useful marker of PD and is expected to be comparable across different SD-OCT equipment. Data of larger groups may be developed in future multicenter studies

The Avascular Zone and Neuronal Remodeling of the Fovea in Parkinson Disease

Inner foveal thinning and intracellular alpha-synuclein were demonstrated in the retina in Parkinson disease. While pathognomonic alpha-synuclein is associated with embryonic dopaminergic (DA) neurons, postmortem studies in the nervous system and retina show prominent effect also in non-DA neurons. We evaluated foveal capillaries and foveal thickness in 23 Parkinson disease subjects and 13 healthy controls using retinal fluorescein angiography and optical coherence tomography. The size of the foveal avascular zone inversely correlates with foveal thinning. Foveal thinning highly correlates with motor impairment and also disease duration. Quantifying capillary and neuronal remodeling could serve as biological markers

Electrophysiological correlates of visual categorization: evidence for cognitive dysfunctions in early Parkinson's disease

Our aim was to examine the electrophysiological correlates of perceptual categorization in Parkinson's disease (PD). We recorded visual event-related potentials (ERPs) in a natural scene categorization task in drug naive idiopathic PD patients and healthy control subjects. In the control group, there was a significant early difference (150-250 ms poststimulus) between ERPs elicited by pictures containing animals and scenes without animals. In spite of relatively preserved basic-level visual functions, this was not observable in the PD group. These results raise the possibility for striatal contributions to visual categorization and may provide a novel protocol for further clinical studies, (C) 2002 Elsevier Science B.V. All rights reserved

Cognitive function in 1736 participants in NINDS Exploratory Trials in PD Long-term Study-1

IntroductionClinical cohort studies suggest that mild cognitive impairment (MCI) is common in early Parkinson's disease (PD). The objectives of this paper were to describe cognitive function in a large clinical trial of early treated PD patients at baseline and over time using two brief cognitive screening tests.MethodsIn total 1741 participants were enrolled in the NINDS Exploratory Trials in Parkinson's disease (NET-PD) Long-term Study-1 (LS-1). The Symbol Digit Modalities Test (SDMT) was collected annually. The SCales for Outcomes in PArkinson's disease-COGnition (SCOPA-COG) was collected at baseline and at year 5. The trial was stopped early based on a planned interim analysis after half the cohort completed 5 years of follow-up. The median length of follow-up was 4 years (range 3-6 years). Predictors of cognitive change were examined using cross sectional (baseline) and longitudinal multivariable linear regression.ResultsThe mean (SD) change from baseline to 5 years was -1.9 (5.1) for the SCOPA-COG and -2.1 (11.1) for the SDMT. Age and baseline UPDRS motor scores were associated with a more rapid decline in SDMT scores and 5 year SCOPA-COG scores. Male gender was associated with more rapid decline in SDMT. Self-reported income was a novel predictor of baseline cognitive function, even adjusted for educational status, although not significantly associated with change over time.ConclusionThis large prospective cohort study demonstrated mild cognitive decline in early treated Parkinson's disease. The study identified income level as a novel predictor of cognitive function

Cortical binocularity in infants.

The primate visual cortex, including that of man, receives separate input from each eye and these interact in binocular cortical neurones. This organization is known to be vulnerable to disruption in early life. To understand the development of human visual cortex, and to detect and assess disorders of binocular function at the earliest possible age, a robust method is needed for detecting binocular interactions in the infant's visual system. We have done this by recording cortical visual evoked responses (VERs) to the onset and offset of binocular correlation in a large-screen dynamic random dot display. We report here that, in general, the human infant has a functional binocular visual cortex by 3 months of age, with some individuals showing cortical binocularity at an earlier age

Autonomic and electrocardiographic findings in Parkinson's disease

Parkinson disease (PD) is a progressive neurodegenerative disorder characterized by motor and non-motor symptoms and signs. Many reports suggest that diminished heart rate variability occurs early, even prior to the cardinal signs of PD. In a longitudinal study of PD, we evaluated whether heart rate variability (HRV) obtained using a 10-second ECG tracing, and the electrocardiographic QT-interval would be associated with PD severity and progression. Subjects were derived from a longitudinal study of 1741 individuals with early, stable PD. The severity of PD was measured using the global statistical test (GST). In a subset, the heart rate corrected QT-interval (QTcB) was calculated for each electrocardiogram (ECG). The HRV was measured for each ECG and then transformed to fit a normal distribution. The baseline analysis included 653 subjects, with 256 completing the 5-year follow up study. There was an association (P<0.05) between QTcB and PD severity in individuals that were taking QT-interval affecting drugs. A longer QT-interval at baseline was associated with more advanced PD at 5years (P<0.05), and greater disease progression over 5years (P<0.05). There was an association between diminished HRV and an orthostatic decrease in standing blood pressure at baseline in individuals with PD (P<0.05). HRV was not associated with PD severity or progression. In conclusion, we were able to detect measurable associations between the QTcB interval and PD severity, PD severity 5years later, and the change in disease over time. However, routine ECG tracings appear inadequate for the evaluation of autonomic function in PD