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Biomedical subjects

T Mulholland

Publications and source records attributed to T Mulholland.

17 recordsLinked to original sources
PubMed1988

Detection of cerebral lateralization of function using EEG alpha-contingent visual stimulation II.

The replicative reliability of durations of alpha-blocking following visual stimulation over different cortical sites was assessed with the method of alpha-contingent stimulation. Fourteen right-handed undergraduates were tested in a randomized factorial design. Words or geometric designs of equal luminance were presented by computer to randomly selected visual half-fields contingent on the occurrence of alpha at one of 4 placements (left and right occipital and left and right temporal). The control (mean/s) of alpha-blocking durations was significantly greater for contralateral visual half-field stimulation compared to ipsilateral visual half-field stimulation. This and other results were interpreted in terms of the concept of replicative reliability of retinal-cortical connections to occipital and temporal lobes and affirm the validity and sensitivity of the method.

Adolescent↗
PubMed1983

Attention and regulation of EEG alpha-attenuation responses.

Two experiments with 16 normal adults of both sexes tested the hypothesis that inattention to a biofeedback display is associated with increased variability of those physiological processes that had been regulated by the biofeedback. Each experiment was a repeated-measures-on-independent-subjects-design. Dependent variables were the time durations and the mean rms power of two mutually exclusive segments of the parietal-occipital EEG: alpha and not-alpha segments. Independent variables were combination of counting tasks and instructions to look at, listen to, and count visual and auditory flashes and clicks. The durations of alpha and not-alpha segments were controlled or regulated by means of an alpha-contingent visual feedback stimulus, Attention to the feedback stimulus was challenged by instructions to count other, noncontingent stimuli. Control of alpha and not-alpha segments was least for conditions of (1) "sham" feedback, and (2) feedback with instructions to count noncontingent auditory clicks, which were presented 3/sec while the feedback visual stimuli were occurring. A new EEG test of attention and distraction was suggested.

Adult↗
PubMed1982

Reduction of variability of EEG occipital, parietal, and central alpha rhythms by visual feedback stimulation.

Two experiments, each with 24 normal right-handed adults, examined variability of the response of EEG alpha rhythms during repeated visual stimulations that were contingent on the occurrence of those rhythms. Within-trial variability of alpha durations and no-alpha (alpha blocking) durations were recorded from bipolar derivations along two bilateral posterior-anterior lines. Variability was significantly lower for: (1) the contingent EEG connected to the stimulus compared to the contralateral EEG, which was recorded simultaneously but was not connected to the stimulus; (2) occipitoparietal EEGs compared to parietocentral EEGs; (3) alpha durations compared to no-alpha durations. Differences in variability among the four EEG locations on the left or the right side were significant for contingent EEGs but not for contralateral nonconnected EEGs. The results were interpreted to be a demonstration that feedback EEG method can be applied to research on the functional topography of an EEG response to sensory stimuli in terms of the reduction of variability of the response that can be achieved with feedback.

Adolescent↗
PubMed1979

Quantification of the human orienting response to another human: lesioned and psychiatric patients compared to normals.

A method for eliciting, controlling, and quantifying the alpha suppression response to a human "real-person" stimulus is presented. Improved control is achieved by a feedback from the EEG response to the presentation of the stimulus. Quantification is comprehensive in that initial response and subsequent habituation for both latency and duration are described. Patients who had suffered a focal lesion but who had recovered sufficiently to travel from one hospital to another by taxi were compared with hospitalized psychiatric patients and normal volunteers. Lesioned patients showed less EEG response to visual stimuli than did the other groups, even with an evocative, real-person stimulus. The differences among the three groups were most evident at the onset of stimulation and less so after habituation had occurred.

Adult↗
PubMed1978

Intermodal relationships in children's perception.

Since judgment of geographical slant requires the use of both optical and postural information, such judgments were used to determine whether intermodal relationships affect children's perception. First, third, and fifth graders made judgments of geographical slant of surfaces depicted in photographs either with or without postural inclination. The results indicate the existence of a linear mechanism which compensates for the effect of postural inclination. Compensation was about 50% of that expected from an ideal perceptual system and did not change with age. The present data are similar to those previously reported for adults and suggest that the compensation process develops early in childhood.

Child↗
PubMed1976

Detection of EEG abnormalities with feedback stimulation.

A feedback method for testing the reactivity of the occipital-parietal EEG in selected brain-lesioned patients revealed abnormalities of (a) insufficient reactivity, (b) bilateral differences in reactivity, and (3) asynchrony. These abnormalities were more evident during feedback stimulation than in the baseline conditions. The utility of feedback method for detecting EEG abnormalities rests on the increased stability or decreased "noisy" variation in the EEG during feedback. The EEG becomes more predictable even to the "on-line" human observer. This makes it easier to detect aberrations or deviations from normal effects. Some effects can only be seen with feedback such as the bilateral differences which occur when the left side controls the feedback compared to when the right side controls it. The results show that feedback EEG is a useful tool in clinical research and indicate that a clinical diagnostic test could be developed with more research. However, the feedback EEG method is not yet a proven diagnostic technique.

Alpha Rhythm↗
PubMed1976

Feedback control and quantification of the response of EEG alpha to visual stimulation.

The response of the posterior EEG alpha thythms to visual stimulation is so variable that it is difficult to obtain reliable on-line measurement of it. Feedback between the EEG alpha and the visual stimulus (1) reduces random variation in the response and (2) facilitates on-line quantification. With feedback EEG, the response to visual stimulation is measured as a series of time durations of alpha and of no-alpha intervals in the EEG. This time series occurs in two stages: an initial disturbance followed by a recovery. The quantification of the series of time durations is achieved by fitting curves to the series of alpha time intervals and of no-alpha time intervals. These functions, computed in each trial of 30 stimulations, are an objective, quantitative definition of EEG response. The utility of the method was demonstrated by testing it with reference to well-known effects. Habituation to a repeated stimulus, dishabituation, habituation to a class of stimuli, dishabituation by changing the class of stimuli, and differences among brain-lesioned, psychiatric patients and normals were shown with a detailed quantification. It was concluded that biofeedback is the method of choice for quantitative research on the EEG component of the human orienting response.

Adult↗
PubMed1966

Electroencephalographic activation: nonspecific habituation by verbal stimuli.

A decrease in the duration of the electroencephalographic activation response to a series of different words: emotional, "neutral," and scrambled occurred. The response to "neutral" words was consistently briefer than that to the other words. This result is evidence of a nonspecific habituation of activation, which implies that habituation to classes of stimuli can occur.

Electroencephalography↗