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Biomedical subjects

J G Beaumont

Publications and source records attributed to J G Beaumont.

At least 37 records · Page 2Linked to original sources
PubMed1984

A critical review of EEG coherence studies of hemisphere function.

Studies of hemisphere function involving the use of coherence analysis are reviewed. Despite the fact that many effects related to subject group and type of task have been reported, few seem to be reliable across studies. The assumptions which seem to underlie the use of coherence analysis are made explicit and discussed. Most investigators consider coherence levels to reflect certain 'baseline' patterns, possibly related to structural connectivity, upon which task and/or strategy effects may be superimposed. Use of a cephalic reference renders coherence effects virtually uninterpretable for a variety of reasons which are fully discussed.

Attention Deficit Disorder with Hyperactivity↗
PubMed1983

Imageability does not interact with visual field in lateral word recognition with oral report.

Four lateral tachistoscopic experiments are reported which tested the hypothesis that the right hemisphere has a selective ability to process highly imageable words (the RH imageability hypothesis). The prediction that performance asymmetry would vary as a function of word imageability, in a lateral recognition task with oral report, was not fulfilled. Results suggested that several previously published studies which hitherto have been regarded as supporting the RH imageability hypothesis may be discounted on artifactual grounds. The implications of these findings for the overall status of the hypothesis were discussed.

Adult↗
PubMed1983

Analysis of sequential letter matching tasks utilising lateralised tachistoscopic presentation.

Four experiments are reported in which sequential matches were demanded for double letter stimuli, the first stimulus pair was presented in central vision and the second in the left or right field. The responses were analysed according to the type of classification required (physical or nominal identify, or different). The results indicated that there were alterations in laterality patterns between retention intervals of 50 msec. and 990 msec. despite evidence for a prolonged and stable form of visual memory. These findings were incompatible with a model of the letter matching task which maps "name" codes to the left hemisphere and "visual" codes to the right.

Dominance, Cerebral↗
PubMed1980

Attentional bias and visual field asymmetry.

In mixed list tachistoscopic presentation of abstract words and random shapes, the probability of word and shape stimuli was varied to generate attentional bias and selective activation of the left or right hemispheres. While a right visual field advantage in accuracy was observed for words, and an effect of stimulus probability was observed across both visual fields in reaction time, no interactions were found between attentional bias and visual field asymmetry. The results can therefore be explained without reference to the attentional model and did not provide evidence of hemispheric activation or priming.

Adult↗
PubMed1979

Late positive component correlates of verbal and visuospatial processing.

Bilateral VERs were elicited by letter stimuli requiring verbal processing and patterns requiring visuospatial processing in a go/no-go reaction time paradigm. The VERS were formed separately to the targets and non-targets of each stimulus type. No VER component displayed hemisphere asymmetries which varied in a task-dependent fashion. However P150 latency was found to be shorter, and N150 amplitude larger, in VERs recorded from the right hemisphere. This is considered to reflect the superiority of the right hemisphere for the early stages of the processing of visual input. P400 latency was shorter and its amplitude larger to the pattern stimuli. In addition, subjects' reaction times were shorter to these stimuli. These results were interpreted in evidence supporting the notion that the late positive component of the ER reflects processes of stimulus evaluation which are not necessarily correlated with those of response selection and execution.

Adult↗
PubMed1979

The specificity of intrahemispheric EEG alpha coherence asymmetry related to psychological task.

Male right handed subjects performed two parallel verbal and nonverbal memory tasks, known to be associated with the anterior temporal lobe, while EEG was recorded from temporal sites referred to either FZ or to linked mastoids. Intrahemispheric coherence and power in the alpha band were calculated. Coherence effects were observed, independent of reference site, which associated the right hemisphere and nonverbal tasks with increased coherence. These effects appear to be relatively specific to more anterior temporal electrode pairs, and confirm previous findings. Power effects demonstrated the difficulty of assessing task-dependent changes independent of reference site, and suggested that specific alpha enhancement may be observed with task involvement. The contribution of coherence analysis to the study of cerebral organisation is discussed.

Alpha Rhythm↗
PubMed1978

Asymmetry in EEG alpha coherence and power: effects of task and sex.

Male and female subjects performed two spatial and two verbal tasks while EEG was recorded from right and left temporal and parietal sites. Measures of alpha band power asymmetry, coherence and phase angle were derived. Spatial tasks produced increased coherence within the right hemisphere. Interhemispheric coherence was higher for females, and at parietal than at temporal sites. Power asymmetry effects confirmed previous findings, reflected upon sex differences in cerebral lateralisation and upon strategies associated with functional cerebral organisation for task performance. The relation to performance studies and the value of the method in investigating dynamic functional organisation are discussed.

Alpha Rhythm↗
PubMed1978

Interhemispheric asymmetries in the visual evoked response: effects of stimulus lateralisation and task.

VER's were elicited by briefly presented lateralised letters in two experiments. In experiment 1 the subjects engaged in verbal processing of the letters and in experiment 2 they engaged in visuospatial processing. In both experiments the latencies of the first two components of the VER's were consistent with previous findings and with the anatomy of the retino-cortical visual pathways. The pattern of hemisphere asymmetries of the amplitudes of the middle and late components differed in the two experiments in that (i) in the second experiment the amplitude of the middle component from the left hemisphere did not vary with field of stimulus presentation although this was the case in the first experiment and (ii) a hemisphere asymmetry (left greater than right) was observed in the late component only in the second experiment. The results are interpreted as evidence of difference in the cerebral processing of the stimuli in respect of the task demands of the two experiments.

Adult↗
PubMed1976

The cerebral laterality of "minimal brain damage" children.

"Minimal brain damage" children and controls matched for age, sex and intelligence were assessed for lateral preference, unimanual motor speed, reaction time to lateralised stimuli and dichotic ear advantage. "Minimal brain damage" children were found to be less extreme and stable in their lateral preferences, slower, and less lateralised in their motor performance. This suggests a deficit of interhemispheric integration, although the groups did not differ in dichotic listening performance, the normal group failing to show the expected ear advantage. "Minimal brain damage" children may be suffering from a partial disconnection syndrome.

Attention Deficit Disorder with Hyperactivity↗
PubMed1973

Clinical assessment of interhemispheric psychological functioning.

A simple method by which the relative performance of the two cerebral hemispheres, and cooperation between the hemispheres, may be assessed in a clinical setting is discussed. The apparatus, which allows the findings of neuropsychological investigations of hemisphere performance in the normal and split-brain subject to be applied in the clinic, is described, together with the results of a preliminary trial and some clinical results.

Adult↗