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Biomedical subjects

R E Saul

Publications and source records attributed to R E Saul.

10 recordsLinked to original sources
PubMed1990

Effects of stimulus degradation on letter-matching performance of left and right hemispheric stroke patients.

Performance on a letter-matching task involving conditions of perceptual degradation was tested on 18 Right CVA patients, 18 Left CVA patients and 18 control subjects. Letter stimuli were presented in three conditions: Clear, Line-Masked, and Blurred. Subjects judged whether two letters of a pair were the same in name or different in name. Right CVA patients performed significantly less accurately than did Left CVA patients and control subjects when letters were perceptually degraded with a line mask overlay or by blurring. No significant differences were found between the two patients groups when the letters were presented without perceptual degradation (the Clear condition), but both patient groups were significantly less accurate than control subjects. The results are similar to findings reported in visual half-field studies with neurologically normal subjects and indicate right-hemisphere superiority for the processing of perceptually degraded visual information.

Adult↗
PubMed1978

Agenesis of the corpus callosum: limits of functional compensation.

Two patients with radiologically confirmed total agenesis of the corpus callosum, and free of gross focal hemispheric pathology, received a battery of lateralized and free-field language and perceptual-motor tests. These tasks allowed a comparison of (1) agenic findings with previous results from surgical commissurotomy patients, and (2) the inter- and intrahemispheric performance for each agenic subject. In general, the results indicate that the two agenic patients do not demonstrate the marked deficits of cross-integration reported after commissurotomy. However, there was an upper limit to their integrative capacity for visual, and to an even greater extent, for fine motor and kinesthetically mediated performance. The tasks that proved particularly difficult appeared to have common factors which may be related to functional capabilities of the ipsilateral motor pathways and anterior commissure.

Adult↗
PubMed1977

Visual evoked response correlates of cerebral specialization after human commissurotomy.

Visual evoked responses (VERS) were recorded from commissurotomy patients and normal subjects in order to investigate the electrophysiological correlates of cerebral lateralization and independent hemispheric processing. A verbal task consisted of detecting rhyming words and a spatial task consisted of comparing matching shapes. Stimuli were delivered, by means of a computer graphic display, into the right visual field, the left visual field, or both visual fields. Behavioral results and evoked response waveforms showed lateralization for verbal processing in the left hemisphere for the patient group. Analysis of variance of product moment correlation coefficients between VER waveforms indicated significant differences between unilateral and bilateral stimulation for both patients and normals. Commissurotomy and normal VERs showed similar patterns of correlation when verbal stimuli were delivered to the left hemisphere, but differed during right hemisphere stimulation. The results are discussed in terms of VER correlates of visual-verbal processing.

Adolescent↗
PubMed1977

Spatial and visuomotor performance with agenesis of the corpus callosum.

The extent to which the cerebral hemispheres and their ipsilateral projection systems compensate for congenital absence of the corpus callosum was studied in an intelligent young adult with radiologically verified total agenesis. She was found to have bilateral speech and the ability to readily integrate visual, tactile, and verbal information simultaneously presented to both hemispheres. However, spatial performance, as demonstrated in blind tactile form board learning, was subnormal compared to normal controls. The results further suggest this impairment, especially severe in the nondominant hand, reflects ipsilateral projection of kinesthetic input, thus maximizing hemispheric competition for motor control of the minor hand. In contrast, the agenic's performance on a simple visuomotor discrimination task (with reduced opportunity for hemispheric interaction) was almost normal. Moreover, she exhibited a doubling of attentional and processing capacity in comparison to the control group. Both hands simultaneously performed this task as rapidly and as accurately as either hand alone. The findings affirm the functionally important, yet limited compensatory role of a developmentally elaborated ipsilateral somatosensory projection system in agenesis of the corpus callosum.

Adult↗
PubMedDate not supplied

Assessment of hepatic encephalopathy with visual evoked potentials compared with conventional methods.

Thirty-six patients with advanced chronic liver disease of predominantly alcoholic etiology and with a documented history or current physical evidence of hepatic encephalopathy were studied and compared to 30 healthy controls. Assessment was made of their mental state, number connection test, venous blood ammonia, electroencephalography and visual evoked potentials with both pattern reversal and flash stimuli. Because of considerable inter- and intraindividual variation in waveform, visual evoked potentials from flash stimuli were considered unreliable. In pattern reversal visual evoked potentials, the latency of the N1 and P1 waves was significantly longer (p less than 0.05) in patients than in controls; however, the wave latencies did not correlate with the mental state score. The mental state score correlated with the number connection test (r = 0.69, p less than 0.001), asterixis (r = 0.36, p less than 0.05), electroencephalography mean dominant frequency (r = 0.44, p less than 0.01) and blood ammonia (r = 0.60, p less than 0.01). In 14 patients studied sequentially, change in the mental state score correlated with change in the number connection test (r = 0.80, p less than 0.01) and asterixis (r = 0.75, p less than 0.01) but not with change in the electroencephalography, blood ammonia or visual evoked potential wave latencies. Although visual evoked potentials are abnormal in patients with alcoholic cirrhosis and encephalopathy, they are less accurate in assessing the level of consciousness than simple bedside evaluation with a number connection test.

Adult↗