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Biomedical subjects

G C Galbraith

Publications and source records attributed to G C Galbraith.

At least 37 records · Page 2Linked to original sources
PubMed1980

Adaptation to visual--motor rearrangement of mentally retarded individuals: relationship to Adaptive Behavior Scale scores.

Thirty-five institutionalized, mentally retarded individuals navigated an obstacle course while viewing through an optical prism that displaced the visual field (visual--motor rearrangement). The degree of adaptation to visual--motor rearrangement was assessed and compared with scores on a research version of the Adaptive Behavior Scale (ABS). The results showed that those individuals who produced the expected patterns of prismatic visual--motor adaptation scored significantly higher on ABS Factors I and II but not III. Factors I and II include a number of items that depend upon sensorimotor integration. Thus, an explicit experimental technique for assessing sensorimotor adaptation was found to support the utility and validity of ABS assessment of mentally retarded individuals.

Adaptation, Psychological↗
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

Electroencephalographic correlates of prism adaptation in mentally retarded individuals.

Sensorimotor adaptation was studied in 23 institutionalized, mentally retarded individuals. This was achieved by recording the pattern of off-target pointing errors resulting from viewing through a 20-diopter prism. The results showed a wide range of individual differences in prism adaptation. The electroencephalogram (EEG) was also recorded from four scalp locations and analyzed by computer to determine EEG intensity, coherence, and phase angle. Correlations between EEG and behavioral scores of prism adaptation revealed a number of significant relationships, especially negative correlations between alpha intensity and prismatic adaptation. These results indicate that patterns of central nervous system activity are meaningful related to sensorimotor capabilities in retarded individuals.

Adaptation, Physiological↗
PubMed1976

A comparison of primary afferent and cortical neurone activity coding sinus hair movements in the cat.

Responses in the somatosensory cortical area S I to stimulation of facial sinus hairs were recorded in the anaesthetized cat and compared with activity in primary afferent fibres innervating vibrissae follicles. The specific cortical vibrissa area is somatotopically organized; 39% of the cortical units in that area responded to stimulation of only a single sinus hair but in some cases all maxillary vibrissae activated a single cortical neurone. The responses consisted of three major groups; either a phasic discharge in response to the movement part of a stimulus, or an additional tonic discharge related to the steady period of vibrissa deflection, or a tonic discharge. On the basis of a comparison of response and excitability characteristics of primary afferent and cortical neurones it is concluded that all four kinds of peripheral units innervating sinus hair follicles project to the somatosensory cortical area S I. It appears from these findings that some cortical neurones receive a specific input related to a particular component of the complex primary afferent response in fibres innervating sinus hair follicles. The results are discussed with respect to previous reports on the central representation of facial sinus hairs in different species.

Afferent Pathways↗
PubMed1975

EEG correlates of visual-motor practice in man.

Special analysis of EEG signals was performed for 15 subjects engaged in three motor tasks of differing difficulty. A measure of average weighted coherence (C) was computed between the six possible combinations of four scalp areas: Oz, C3, C4 and Fz. In all subjects, regardless of task, scalp recordings over cortical areas known to have relatively dense fiber connections had significantly greater C values. However, the effects of task difficulty and practice were superimposed upon this basic pattern. Thus, the most difficult task (pursuit-rotor tracking) resulted in the highest coherence levels, while the least difficult task (visual tracking only of the pursuit-rotor disk) resulted in the lowest coherence levels. Practice, on the other hand, was associated with a significant decrease in overall level of coherence. This decrease is consistent with an interpretation of reduced task difficulty due to visual-motor learning. The results of the present study suggest that patterns of scalp EEG coherence may reflect some aspects of the underlying pattern of anatomical pathways, as well as the more dynamic properties of task difficulty and visual--motor practice.

Adolescent↗
PubMed1975

Effect of preconditioning visual stimulus duration on visual-evoked responses to a subsequent test flash in Down's syndrome and nonretarded individuals.

Visual-evoked responses to a visual test flash preceded by three different durations of a visual conditioning flash having the same intensity and form were recorded from 8 Down's syndrome subjects and 9 nonretarded CA-matched control subjects. Both groups showed a significant decrease in visual-evoked response perimeters to the test flash as the duration of the visual conditioning flash increased from 1 to 100 msec. For the 1000-msec condition, perimeters of Down's syndrome subjects showed a significant increase, and this was significantly greater than the nonretarded group. These results suggest that Down's syndrome individuals have deficits in their neural processing of sensory information.?23Author

Adolescent↗