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Biomedical subjects

E Adachi-Usami

Publications and source records attributed to E Adachi-Usami.

At least 127 records · Page 7Linked to original sources
PubMed1985

Pattern-evoked cortical potentials and nuclear magnetic resonance imaging in total and partial agenesis of the corpus callosum.

We have examined two cases of agenesis of the corpus callosum without any associated abnormalities. They were accidentally detected in X-ray-computed tomography. Total agenesis of the corpus callosum could be differentiated by nuclear magnetic resonance imaging from partial agenesis. They had moderately depressed stereopsis. Visually evoked cortical potentials to pattern stimuli showed abnormal findings in binocular viewing, and VECP equi-potential maps were similar to those of normal controls.

Adult↗
PubMed1985

Electrophysiological studies on Kirisawa type uveitis (acute retinal necrosis).

Kirisawa type uveitis (acute retinal necrosis) is characterized by a necrotizing retinitis, heavy vitreous opacities, retinal vasculitis, and subsequent retinal detachment. Not only the etiology but also the clinical findings of this disease have not yet been defined. In the preceding year we have seen four patients whose clinical course and findings were similar to each other. In two of them a vitrectomy and an encircling operation have been performed before retinal detachment occurred. This treatment has found to be effective. In all 4 cases electrophysiological examinations were done at various stages of the disease. ERGs following pattern and flash stimuli varied in accordance with retinal changes, while VECPs were less strongly affected as ERGs. Results are discussed referring to fluorescein angiographic findings and ocular changes.

Adult↗
PubMed1984

Equipotential maps of pattern-evoked potentials in man.

Pattern-evoked cortical potentials for half field stimuli were recorded from 16 electrodes on the scalp, and equipotential maps were constructed. For right and left half field stimuli, the maximal values of the maps were found over the hemisphere ipsilateral to the visual half field stimulated. For lower half field binocular stimuli, the maxima were more anterior than for monocular stimuli (for upper field stimuli, inverted location differences were found). In hemianoptic patients, the maxima were obtained over the impaired hemisphere regardless which part of the visual field was stimulated. The maxima of pattern-evoked ERG fields on the face were found around the stimulated eye.

Depth Perception↗
PubMed1983

Monocular and binocular evoked average potential field topography: upper and lower hemiretinal stimuli.

Scalp potentials evoked by monocular and binocular 2/s checkerboard reversals with checks of 56 or 14 min were recorded from four midline electrodes between inion and 7.5 cm above inion vs a common anterior reference in 31 normals. The electrode location and latency of the evoked maximal occipitally positive potential difference between any 2 of the 5 electrodes, between 80 and 140 ms latency was determined in each run. Mean maximum locations over subjects for upper hemiretinal, binocular stimuli were more anterior than for monocular stimuli; for lower hemiretinal stimuli, inverted location differences were found. Binocular responses also had shorter latencies than monocular responses. Since area 18 is more anterior to 17 for upper, more posterior to 17 for lower hemiretinal projection to cortex, the results suggest that neurons which respond only if both eyes are simultaneously stimulated are more frequent in higher than lower order visual areas.

Biophysical Phenomena↗
PubMed1983

Distribution of pattern-evoked potentials in the facial area.

We studied the spatial distribution of the pattern-evoked potentials on the face with a simultaneous 16-channel recording system. The results showed that the responses had their first positive component at the peak latency of 52.0 +/- 1.9 (S.E.) msec. The maximum potential value within the equipotential maps was in the region around the stimulated eye in eight normal subjects. One patient with one enucleated eye showed the maximum value within the map only around the fellow eye; much later, at a peak latency of approximately 100 msec, we obtained a response with a maximum on the scalp around the inion. In another patient with long-standing optic nerve disease, the pattern-evoked potentials were absent but the flash-evoked potentials were normal, showing the maximum value in the region near the stimulated eye.

Adult↗
PubMed1982

Contrast thresholds of diabetic patients determined by VECP and psychophysical measurements.

VECPs to checkerboard pattern reversal (12 Hz reversal) at different contrast levels were measured in normal subjects and in patients suffering from diabetes mellitus, with visual acuities above 0.8. VECP contrast threshold was obtained by extrapolating VECP amplitude vs contrast on a log scale to zero microV. Results were compared with psychophysical thresholds. It was shown that both VECP and psychophysical contrast thresholds were significantly higher in the diabetic patients than in the normal subjects.

Adolescent↗
PubMed1981

Human visual system modulation transfer function measured by evoked potentials.

Visual potentials evoked by checkerboard pattern reversal were studied using temporal frequencies between 3 and 12 Hz (i.e. 6 and 24 reversal per sec, with sinusoidal or square wave modulation). Sinusoidal modulation evoked lower amplitude potentials than square wave modulation, at all frequencies used. Evoked potential amplitude vs temporal stimulation frequency curves for both modulations showed a maximum at approximately 4 Hz, with a slight decrease for lower frequencies, and a steep fall-off for higher frequencies starting at 7 Hz (values beyond 12 Hz were not measurable), unlike de Lange's psychophysical data. Accordingly, different brain generators are hypothesized for evoked potentials and psychophysical functions.

Brain↗
PubMed1979

Comparison of contrast thresholds of large bars and checks measured by VECPs and psychophysically as a function of defocusing.

The effects of defocusing the image on the contrast threshold were studied both for checkerboard and bar patterns at various low spatial frequencies, and comparison was made between psychophysical results and visually evoked cortical potentials (VECPs) results. VECP threshold was defined as the contrast necessary for obtaining a criterion amplitude of 5 muV. When increasing the degree of defocusing, the lowest contrast threshold shifted towards larger checks or bars, the contrast threshold increased more abruptly for smaller sizes, and the VECP contrast thresholds increased more than the psychophysical ones, especially for smaller sizes. No significant difference was found in the contrast thresholds between the results with bar patterns and checkerboard patterns, except that for bars, the VECP threshold as defined was approx. 0.2 log units higher than those for checkerboard.

Differential Threshold↗
PubMed1978

Scotopic retinal sensitivity in man as determined with visually evoked cortical potentials.

Scotopic properties of the peripheral retina in man was studied by recording visually evoked cortical potentials (VECPs). The intensity required for a criterion latency of the scotopic VECP was compared with the sensory threshold in a number of situations where the stimulating retinal site and the area of the stimulus were altered. With circular spot stimulation, the VECT amplitude attenuated greatly as the stimulus site moved to peripheral 10 degrees and was almost null when stimulation was made outside it. However, within the retinal area from the fovea to peripheral 10 degrees, the VECP sensitivity was found to vary according to the rod distribution, as suggested from the sensory threshold. Stimulation with annular patterns revealed that the parallelism between the VECP sensitivity and the rod distribution holds good within up to 30 degrees from the fovea. A strong summation was proved to be operative for eliciting VECPs by stimulation of the peripheral retina.

Adult↗