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Biomedical subjects

A Gale

Publications and source records attributed to A Gale.

At least 37 records · Page 2Linked to original sources
PubMed1985

Combined carotid coronary reconstructions--synchronous or sequential?

Analysis of 16 synchronous with 26 sequential combined carotid coronary reconstructions showed no statistical advantage of either approach. Sequential operations are more convenient but increase the total operating time by an hour or so. Synchronous operations can be carried out without carotid shunting despite hypotension provided hypothermia is established. In other circumstances the internal carotid back pressure is used to indicate the need for carotid shunting. In the 42 patients there were three strokes (7%) including one fatal stroke (2%) and two myocardial infarctions, both fatal (5%).

Cardiopulmonary Bypass↗
PubMed1982

EEG correlates of hemisphere differences during a rapid calculation task.

Twenty male subjects performed a continuous task involving response to digit sets. The subject was required to respond to sets containing only odd numbers, and whose sum was greater than or equal to 20. Abundance of both left and right hemisphere EEG was inversely related to the number of odd digits in a set, showing accumulation of cortical arousal in response to cue value. This effect was stronger for the left hemisphere in some of the frequency bands. Reaction time correlated with EEg parameters for the left hemisphere only. This study overcomes many of the methodological flaws of earlier work. Differences obtained between hemispheres are thought to reflect both the exertion of mental effort in general and rapid calculation in particular.

Adolescent↗
PubMed1979

An EEG study of visual attention in schizophrenic patients and normal controls.

This is a series of experiments examining the EEG, both at rest and in response to visual stimuli of varied complexity, in schizophrenics and normal controls. Subjects attended on several occasions. The resting EEG of patients was more activated than that of normals on all sessions, although only the patients showed diminished activation as a function of visits. The EEG of normals responded systematically on all occasions, but the patients showed similar response only under conditions of instructional set prescribing active stimulus appraisal. For both groups, subsequent stimulus recognition scores were correlated positively with EEG discrimination of stimuli during inspection. Within the patient group, several measures of pathology correlated both with recognition performance and several EEG parameters. Thus the present study draws together data demonstrating attentional deficit, heightened arousal, and reduced cortical variability in schizophrenics. Attention is drawn to methodological difficulties inherent in this type of study.

Adult↗
PubMed1979

Short-term recall of nine-digit strings and the EEG.

In three exploratory studies, EEG changes were monitored while subjects performed a nine-digit recall task. Experiment 1 involved auditory presentation without practice or prior instruction. EEG characteristics measured before the task related to subsequent recall, EEG activation increased progressively during digit presentation and rehearsal, and several between- and within-subject analyses showed increased activation to be associated with poor recall performance. In Expt. 2 the digits were presented visually and subjects were given instruction and practice in an efficient rehearsal strategy. Recall performance improved but its relationship with the pre-task EEG disappeared. Activation increased with digit presentation but the relationship between the EEG and performance was complex since a within-subject analysis associated decreased activation with better performance (as in Expt. 1) while this relationship was reversed in a between-subject analysis. The results are explained both in terms of traditional findings relating activation to recall, and drive theory accounts of learning and performance. Finally, Expt. 3 demonstrated that performance was better, both in the morning (compared with the evening) and on a second testing session. There were complex time of day effects for the EEG, with lower and higher measured frequencies yielding higher voltage output in the evening and intermediate frequencies showing a reverse effect. In summarizing the data from the three experiments it is suggested that different EEG frequencies are differentially sensitive to different conditions (task specific factors, stimulus input characteristics, knowledge of success and failure, degree of task mastery and circadian variation).

Arousal↗
PubMed1978

Changes in the EEG as the subject learns to recall.

The EEG was monitored from posterior leads located above the left and right hemispheres, while the subject learned to recall visually presented 9-digit strings. Processing of material to be recalled led to systematic and progressive activation of the left hemisphere together with an increasing ratio in the EEG activity of the two hemispheres. As performance improved with practice, the initial activation (during the first six digits) was followed by deactivation just prior to recall. This is interpreted as reflecting a shift from active processing (rehearsal) to passive processing (echoic buffer storage). Subjects who recalled well more activated in the left hemisphere than in the right and the level of EEG activity in the left hemisphere during early trials predicted overall recall performance throughout the task. Activity in the right hemisphere was unresponsive to the presentation of material and unrelated to performance. This study shows therefore that: (i) rehearsal for short term recall is a function of left hemisphere activity, (ii) individual differences in left hemisphere activity predict performance, and finally (iii) dynamic changes in brain organisation accompany an overall improvement in performance.

Brain↗
PubMed1977

EEG, measures of complexity, and preference for nonrepresentational works of art.

With a heterogenous sample of human subjects, alpha abundance, an inverse function of cortical arousal, was found to increase with greater complexity of a series of 18 nonrepresentational works of art. This finding is contrary to those of previous EEG studies with artifically generated stimuli, which showed increased arousal with increasing complexity; but is consistent with those which reveal an interverted-U-shaped relation between arousal and complexity when the range of complexity sample is broad. That is, at higher levels of complexity, subjects may be less able to process the information content of paintings. Ratings of interestingness and pleasingness increased with complexity; it may be that they are dependent to some extent on social learning factors.

Adolescent↗
PubMed1976

Bilateral EEG differentiation of stimuli.

The EEG of both right and left hemispheres was monitored while subjects were presented with words, music, arithmetical problems and abstract pictures, (15 trials of each treatment, 9 sec per trial). The left side of the brain was most activated during presentation of words and arithmetic, whilst the right side of the brain was most activated during presentation of music. In addition, the right side was more activated during exposure to arithmetic than to words. The pictures were not differentiated by either side of the brain and it is possible that they had the effect of deactivating or relaxing subjects, since they yielded high abundance values compared with other stimuli. This study confirms earlier findings showing significant between-hemisphere ratios for arithmetic and words. In addition, however, the within-hemisphere analyses show that music affects the right hemisphere (without inducing between-hemisphere changes) and that arithmetic also activates the right hemisphere if compared with the non-activating effects of words.

Adult↗
PubMed1975

EEG correlates of eye contact and interpersonal distance.

The EEG of 18 male subjects was monitored while the subject gazed at the eyes of a male experimenter located 2, 4, 8, 16 or 32 ft from the subject. The experimenter either gazed directly at the subject or averted his eyes. EEG arousal was highest when the experimenter was at 2 ft and gazing into the subject's eyes. EEG arousal diminished as a function of distance, while arousal for direct gaze was always higher than for averted gaze, whatever the distance.

Adolescent↗
PubMed1975

Stimulus complexity, EEG abundance gradients, and detection efficiency in a visual recognition task.

Occipital EEG was monitored while subjects inspected 27 projected patterns. The number (N) and variety (V) of elements in the patterns were varied systematically. There were three levels of N (6, 12 or 24 elements) and three levels of V (circles, squares or hexagons occupying all, one half or one third of the element locations for all levels of N). Subjects were instructed that they would be required in a post-test to recognize the patterns, among patterns which had not appeared; they were also informed that the patterns had been constructed according to a set of simple rules, but the nature of these rules was not made fully explicit. The EEG was quantified by means of low-frequency analysis, yielding measures of abundance (theta, alpha and beta) and mean dominant frequency. For the recognition task, nine stimulus items were embedded among 45 items. Recognition efficiency was measured by means of the signal detection theory discrimination index (d'). The results were as follows: (i) Both N and V were inversely related to alpha abundance (P less than 0-01); (ii) the strongest relationship between stimulus parameters and the EEG held for N and EEG beta activity (13-5-19-5 Hz;P less than 0-001), where again the EEG and N were inversely related; (iii) there was a significant (P less than 0-05) direct relationship between N and theta activity; (iv) contrary to prediction, mean dominant alpha frequency decreased as N increased; (v) d' correlated significantly with a number of effects for N, i.e. subjects who exhibited greatest EEG discriminability of items during exposure of the patterns, subsequently obtained the higher detection scores in the recognition task. The work described therefore demonstrates that only only do stimulus parameters have systematic effects upon brain activity as measured by the EEG, but that such effects have functional value and reflect aspects of efficiency. The results are fully compatible with arousal theory constructs relating physiological reactivity and performance.

Adolescent↗