Luminance-onset, pattern-onset and pattern-reversal evoked potentials in human albinos demonstrating visual system anomalies.
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Biomedical subjects
Publications and source records attributed to D Creel.
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Visually evoked potentials recorded from two types of human ocular albinos demonstrated significant hemispheric asymmetry following monocular stimulation. The asymmetry is indicative of disorganization of retinogeniculostriate projections similar to that reported for mammals with total albinism. Abnormal optic projections are associated with lack of ocular pigment and are not associated with any specific generalized pigment defect.
A dose of alcohol producing a mean blood alcohol concentration of 0.09% slowed the peak of later components of visually evoked potentials recorded from the occipital scalp. Simple visuomotor reaction time was also slower in a low-motivation nonreward condition.
The retinogeniculate fiber projections were studied by degeneration methods in several strains of rats with pigmentation in their eyes and pelts ranging from the intensely pigmented self phenotype to the albino. The ipsilateral retinogeniculate input in the self, Irish, and hooded rats, and rats with "bicolor fundus" is located medially within the dorsal alteral geniculate nucleus (LGd) and is seen as a single lamina of moderately dense degeneration.
Cytochrome P-450 levels were analyzed in rats of two pigmented (black Long-Evans and ACI) and two albino strains (Fischer 344 and Sprague-Dawley) following the administration of pentobarbital sodium and physiological saline. Differences between the albino vs pigmented strains were observed following injections of saline. The Fischer 344 albino strains responded similarly to the pigmented strains following a progressively increasing dose schedule of pentobarbital sodium.
The study examined the effect of a dose of alcohol producing a mean blood alcohol content of 90 mg% on components of the scalp-recorded visually evoked potential (VEP) both with and without a visual discrimination task to control the level of attention, and the interaction of amplitudinal hemispheric asymmetry of the VEP with alcohol treatment and the discrimination task. Ingestion of ethyl alcohol producing a mean blood alcohol content of 90 mg% affected VEPs recorded from the central scalp by attenuating the overall amplitude of the later VEP components (60-200 msec) and by significantly reducing hemispheric asymmetry in the amplitude of these VEP components. Alcohol attenuates VEP components P90-N120 and N120-P180, and the task of counting flashes and attending to discriminate double flashes increased amplitude of VEP components N60-P90 and P90-N120 in control and placebo conditions. Several studies have reported that the VEP recorded from the right hemisphere of human beings is larger than the VEP recorded from the homologous location in the left hemisphere. Evoked potentials recorded under control and placebo conditions in this study also demonstrated a hemispheric asymmetry with right larger than left for component P90-N120. We also found a reliable alcohol by hemispheric asymmetry interaction. Alcohol selectively depressed the amplitude of the right hemisphere VEP (P90-N120) component to a significantly greater extent than the left hemisphere VEP was affected.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Auditory abnormalities were evaluated in human albinos using temporary threshold shift and dichotic listening tasks. Albinos exhibited a greater temporary threshold shift than did normally pigmented individuals after exposure to a fatiguing tone. In the dichotic listening task, albinos demonstrated a significantly larger right ear advantage than normally pigmented individuals. These results support earlier work indicating that hemispheric asymmetries are present in a albino auditory system and suggest that abnormalities may be present at the cochlear level as well.