Personality variables and alpha enhancement: a correlative study

The lateralized processing of affect in emotionally labile extraverts and introverts: central and autonomic effects

The purpose of the present study was to better understand both the lateralized hemispheric processing of emotion and the differential neural processing of arousal in extraverts and introverts. We preselected right-handed male and female extraverts and introverts who were high in emotional lability. Each subject was exposed to two positive and two negative emotional stimuli under each of three counterbalanced conditions, including affective, cognitive, and neutral, while EEG and electrodermal activity (EDA) were recorded. Results showed that introverts are more aroused and that extraversion interacts with gender to produce differentiated patterns of lateralized neural activity. In addition, affective conditions produced higher levels of arousal than did cognitive or neutral conditions, particularly in the left hemisphere and under negative as opposed to positive stimuli. Finally, the hemispherically differentiated processing of positive and negative stimuli was affected by the contextual conditions under which they were experienced.

Extraversion and the EEG: I. An evaluation of Gale's hypothesis

The hypothesis of A. Gale that extraverts differ from introverts in EEG defined arousal only under moderately arousing conditions is examined. It is argued that the hypothesis is not entirely internally consistent and lacks empirical support. A re-analysis of the literature on which it was based points to problems in the measurement of extraversion as a more significant source of confounding than variation in conditions of testing.

Effects of health locus of control and health value upon EMG biofeedback training

Subjects who scored highly internal or external on a health locus of control scale and who scored high or low on the value each attached to good health were each given two sessions of frontalis EMG biofeedback training in accordance with a 2 x 2 x 2 factorial design. It was predicted that both internality and high health value would be positively associated with ability to control EMG and that these influences would combine additively. The predictions were not supported but a significant interaction between internality and health value was found. This interaction could be explained by assuming that both internality and high health value increased drive which in turn produced greater muscle tension, the relationship between drive and muscle tension being an ascending sigmoid function.

Effects of true and inverted feedback on integrated occipital alpha

Ambient illumination had no effect on baseline levels of alpha of 20 female university students who had their eyes closed, and significant increases from these levels were obtained through true but not inverted feedback procedures. These results indicate that alpha enhancement can be obtained in a manner that is not explicable in terms of disinhibition processes.

Methodological issues in alpha biofeedback training

Current controversies concerning outcomes of EEG alpha feedback training are at least in part due to methodological differences among different studies. The aim of this paper is to provide future and present researchers in this field with an analysis of methods used in most of the studies published from 1968 to 1976, and to comment on those methodological issues we think most important. These include alpha assessment, training schedules, and uni- versus bidirectional training. This analysis is accomplished in part by a series of tables listing 45 studies and the detailed methodologies used. It is believed that the probabilities of successful feedback enhancement of alpha can be substantially improved by incorporating the following suggestions: (a) employing at least four training sessions, (b) the use of continuous rather than dichotomous feedback, supplemented by periodic quantitative scores of progress, and (c) using training trials of at least 10 minutes' duration.

Resting levels of alpha and the Eysenck Personality Inventory

The number of microvolt seconds of alpha rhythm emitted during a five-minute period were collected for 30 male and 30 female subjects. This measure of alpha abundance was then compared in subjects who scored high and in those who scored low on the E and N scales of the Eysenck Personality Inventory. Subjects who scored low on the E scale tended to have a significantly greater number of microvolt seconds of alpha than did subjects who scored high on the scale. No differentiation on the basis of emitted alpha was possible for subjects scoring high and low on the N scale.

alpha and EMG feedback training in the prevention of drug abuse. A controlled study

Seventy-five college students who were regular drug users were randomly assigned to five experimental groups: alpha feedback, EMG feedback, joked feedback, no-feedback and no-treatment. All treated subjects participated in twelve 30-minute training sessions, four in the laboratory and eight at the college, over a period of four weeks.

At the end of the final session, the alpha group had a significantly higher adjusted mean alpha level than the EMG and no-feedback groups but this disappeared during follow-up. The EMG group had a significantly lower adjusted mean EMG value than the alpha, no-feedback and no-treatment groups, which was maintained during follow-up while feedback was present and, to a less substantial degree, when feedback was not present. There were no significant differences between treatment groups as regards the adjusted mean alcohol or cigarette consumption and sleep parameters.

Concerning drug use, among medium users (6–13 times monthly), the EMG feedback group had a consistently significantly lower adjusted mean drug use after treatment and at the one- and three-month follow-ups than the no-treatment group. Among high users, subjects who received feedback (alpha, EMG or joked) tended to reduce their drug use compared to pre-treatment levels, whereas those in the no-feedback or no-treatment groups experienced an increase.

Since drug use was the only variable appreciably influenced by feedback training, the results tend to suggest that EMG feedback could serve as a means for the prevention of drug abuse, particularly for patients where anxiety is a predisposing factor.

Conflicting results in EEG alpha feedback studies: why amplitude integration should replace percent time

Success or failure of EEG feedback training for alpha enhancement can depend on how alpha activity is quantified and fed back. Alpha-enhancement failures usually employ a percent time (%) technique; successes typically use amplitude integration (variation of). To dramatize the differences between percent and integration techniques, we derived both measures simultaneously from left occipital (O1) and left central (C3) sites for 16 male subjects who were given 5.6 hours of integrated alpha feedback from the midline occipital (Ozeta) site. At both the O1 and C3 sites the integrated and percent measures were not equivalent and not linearly related. Statistically significant differences in the (integrated, percent) correlation coefficients (z-transpormed) were observed under the different recording conditions: alpha enhancement, alpha suppression, and baselines. Theoretical discussion of integration and percent techniques is given and the adoption of amplitude integration measures and feedback stimuli is strongly advocated.