Recognition of aspects of consciousness through association with EEG alpha activity represented by a light signal

An EEG-based attention recognition method: fusion of time domain, frequency domain, and non-linear dynamics features

Introduction

Attention is a complex cognitive function of human brain that plays a vital role in our daily lives. Electroencephalogram (EEG) is used to measure and analyze attention due to its high temporal resolution. Although several attention recognition brain-computer interfaces (BCIs) have been proposed, there is a scarcity of studies with a sufficient number of subjects, valid paradigms, and reliable recognition analysis across subjects.

Methods

In this study, we proposed a novel attention paradigm and feature fusion method to extract features, which fused time domain features, frequency domain features and nonlinear dynamics features. We then constructed an attention recognition framework for 85 subjects.

Results and discussion

We achieved an intra-subject average classification accuracy of 85.05% ± 6.87% and an inter-subject average classification accuracy of 81.60% ± 9.93%, respectively. We further explored the neural patterns in attention recognition, where attention states showed less activation than non-attention states in the prefrontal and occipital areas in α, β and θ bands. The research explores, for the first time, the fusion of time domain features, frequency domain features and nonlinear dynamics features for attention recognition, providing a new understanding of attention recognition.

Alpha activity neuromodulation induced by individual alpha-based neurofeedback learning in ecological context: a double-blind randomized study

The neuromodulation induced by neurofeedback training (NFT) remains a matter of debate. Investigating the modulation of brain activity specifically associated with NF requires controlling for multiple factors, such as reward, performance, congruency between task and targeted brain activity. This can be achieved using sham feedback (FB) control condition, equating all aspects of the experiment but the link between brain activity and FB. We aimed at investigating the modulation of individual alpha EEG activity induced by NFT in a double-blind, randomized, sham-controlled study. Forty-eight healthy participants were assigned to either NF (n = 25) or control (n = 23) group and performed alpha upregulation training (over 12 weeks) with a wearable EEG device. Participants of the NF group received FB based on their individual alpha activity. The control group received the auditory FB of participants of the NF group. An increase of alpha activity across training sessions was observed in the NF group only (p < 0.001). This neuromodulation was selective in that there was no evidence for similar effects in the theta (4-8 Hz) and low beta (13-18 Hz) bands. While alpha upregulation was found in the NF group only, psychological outcome variables showed overall increased feeling of control, decreased anxiety level and increased relaxation feeling, without any significant difference between the NF and the control groups. This is interpreted in terms of learning context and placebo effects. Our results pave the way to self-learnt, NF-based neuromodulation with light-weighted, wearable EEG systems.

Changes in EEG Brain Connectivity Caused by Short-Term BCI Neurofeedback-Rehabilitation Training: A Case Study

Background

In combined with neurofeedback, Motor Imagery (MI) based Brain-Computer Interface (BCI) has been an effective long-term treatment therapy for motor dysfunction caused by neurological injury in the brain (e.g., post-stroke hemiplegia). However, individual neurological differences have led to variability in the single sessions of rehabilitation training. Research on the impact of short training sessions on brain functioning patterns can help evaluate and standardize the short duration of rehabilitation training. In this paper, we use the electroencephalogram (EEG) signals to explore the brain patterns’ changes after a short-term rehabilitation training.

Materials and Methods

Using an EEG-BCI system, we analyzed the changes in short-term (about 1-h) MI training data with and without visual feedback, respectively. We first examined the EEG signal’s Mu band power’s attenuation caused by Event-Related Desynchronization (ERD). Then we use the EEG’s Event-Related Potentials (ERP) features to construct brain networks and evaluate the training from multiple perspectives: small-scale based on single nodes, medium-scale based on hemispheres, and large-scale based on all-brain.

Results

Results showed no significant difference in the ERD power attenuation estimation in both groups. But the neurofeedback group’s ERP brain network parameters had substantial changes and trend properties compared to the group without feedback. The neurofeedback group’s Mu band power’s attenuation increased but not significantly (fitting line slope = 0.2, t-test value p > 0.05) after the short-term MI training, while the non-feedback group occurred an insignificant decrease (fitting line slope = −0.4, t-test value p > 0.05). In the ERP-based brain network analysis, the neurofeedback group’s network parameters were attenuated in all scales significantly (t-test value: p < 0.01); while the non-feedback group’s most network parameters didn’t change significantly (t-test value: p > 0.05).

Conclusion

The MI-BCI training’s short-term effects does not show up in the ERD analysis significantly but can be detected by ERP-based network analysis significantly. Results inspire the efficient evaluation of short-term rehabilitation training and provide a useful reference for subsequent studies.

Distinguishing Voluntarily Upregulation of Localized Central Alpha from Widespread Posterior Alpha

Neurofeedback (NF) training based on alpha upregulation has been widely used on patient and healthy populations. However, active voluntary modulation of central or widespread posterior alpha in response to central alpha feedback is still ambiguous. The objective of this study is to confirm whether patients learn to truly increase alpha power and to determine if patients modulate central or widespread alpha power when alpha feedback is provided from central brain region. This EEG-based NF study was conducted on seven paraplegic patients with same injury type, pain location, and sensitization to ensure homogeneity. In addition to routine NF training sessions, various experiments were performed to compare alpha NF modulation received from C4 with alpha shift during cognitive tasks, occipital or parieto-occipital cortex, and Laplacian montage which is expected to separate localized alpha from widespread alpha, to attain objectives. Moreover, imaginary coherence analysis in alpha band was also performed to check whether C4 training site is coupled with other brain regions and to confirm whether activity at training site leads/lags the activity of other brain regions. The results indicate widespread alpha modulation in patients during regular NF sessions (p < 0.05) with large effect size (> 0.8), sufficiently high statistical power (> 80%), and a narrower confidence interval (CI) in response to NF provided from the central brain region reflecting less uncertainty and higher precision. However, small effect size obtained with Laplacian montage require patients to be trained with Laplacian feedback to achieve a reliable conclusion regarding localized alpha modulation. The outcomes of this study are not only limited to validate true alpha modulation in response to central alpha feedback but also to explore the mechanism of central alpha NF training.

Alpha Neurofeedback Has a Positive Effect for Participants Who Are Unable to Sustain Their Alpha Activity

Alpha rhythm (8-13 Hz) is linked to relaxed mental state in humans. Earlier reports have shown that individuals can increase their alpha power if provided with a valid feedback, compared to controls who are provided invalid feedback. However, these results remain controversial, partly because controls may be in a different behavioral state, making it difficult to directly compare their alpha power with the valid group. We here address this issue by using an experimental paradigm in which an invalid feedback is given on a fraction of trials, such that both valid and invalid conditions can be obtained from the same participant. Using electroencephalography (EEG), we recorded alpha power from the occipital area from 24 humans (nine females) and played a feedback tone which could be valid (tone frequency proportional to alpha power), invalid (tone sequence from a previous valid trial; participants were unaware of this condition), or neutral (constant tone frequency). We found that during eyes closed-state, neurofeedback did not enhance alpha activity beyond pre-trained state within the experimental duration, probably because of saturation of alpha rhythmicity. However, for participants whose alpha power decreased over time within a trial, valid feedback helped them to sustain alpha more than invalid feedback. Further, alpha increase showed a weak negative correlation with their self-reported attentional load but was uncorrelated with relaxation levels. Our results reconcile many conflicting reports in the neurofeedback literature, and show that even under most stringent control, valid neurofeedback can help participants who are otherwise unable to sustain their alpha activity.

Individual EEG alpha profiles are gender-dependent and indicate subjective experiences in Whole-Body Perceptual Deprivation

We use a unique environment of Whole Body Perceptual Deprivation (WBPD) to induce an altered state of consciousness (ASC) in our participants, and employ online EEG recording. We present individual EEG alpha profiles, and show how these data can be analyzed at the individual level. Our goal is to investigate to what degree subjective experience matches EEG alpha profile, and in particular, the various alpha hemispheric asymmetries observed in the frontal, parietal, and occipital lobes. Specifically, we consider positive (frontal L < R) or negative (frontal L > R) affect; a more verbal (L > R) or a more imagistic (R > L) mode of thinking; and a more trancelike (frontal > parietal) or more reflective (frontal < parietal) state of consciousness. Our results indicate that the individual alpha profiles are reflected in individual differences in subjective experience. However, the alpha profiles are confounded with the gender of the participant. Specifically, there is a predominant R > L asymmetry found for male participants, and a predominant L > R asymmetry found for female participants.

Massed and Spaced Practice in Alpha Enhancement

Spaced practice (20 min. work, 24 hr. rest) was more efficient for 4 trials than massed practice (20 min. work, 90 sec. rest) in the learning of alpha enhancement by undergraduate women ( Ns = 10) While the spaced group doubled their production of alpha, the massed group demonstrated almost no improvement.

Relationship between Internal and External Locus of Control and the Operant Conditioning of Alpha through Biofeedback Training

Subjects were identified as internally oriented ( N = 15) and as externally oriented ( N = 15) as determined by scores on the Locus of Control scale. They were given training to increase the density of occipital EEG waves in the alpha (8 to 13 Hz) frequency band through an auditory feedback loop keyed to the alpha, informing subjects when they were emitting the desired pattern. Both groups were successful in increasing the density of alpha waves; internally oriented subjects were, however, better able to enhance their alpha production (frequency) than were externally oriented subjects.

The effect of multimodal and enriched feedback on SMR-BCI performance

OBJECTIVE

This study investigated the effect of multimodal (visual and auditory) continuous feedback with information about the uncertainty of the input signal on motor imagery based BCI performance. A liquid floating through a visualization of a funnel (funnel feedback) provided enriched visual or enriched multimodal feedback.

METHODS

In a between subject design 30 healthy SMR-BCI naive participants were provided with either conventional bar feedback (CB), or visual funnel feedback (UF), or multimodal (visual and auditory) funnel feedback (MF). Subjects were required to imagine left and right hand movement and were trained to control the SMR based BCI for five sessions on separate days.

RESULTS

Feedback accuracy varied largely between participants. The MF feedback lead to a significantly better performance in session 1 as compared to the CB feedback and could significantly enhance motivation and minimize frustration in BCI use across the five training sessions.

CONCLUSION

The present study demonstrates that the BCI funnel feedback allows participants to modulate sensorimotor EEG rhythms. Participants were able to control the BCI with the funnel feedback with better performance during the initial session and less frustration compared to the CB feedback.

SIGNIFICANCE

The multimodal funnel feedback provides an alternative to the conventional cursorbar feedback for training subjects to modulate their sensorimotor rhythms.

Effect of Muslim prayer (Salat) on α electroencephalography and its relationship with autonomic nervous system activity

OBJECTIVES

This study investigated the effect of Muslim prayer (salat) on the α relative power (RPα) of electroencephalography (EEG) and autonomic nervous activity and the relationship between them by using spectral analysis of EEG and heart rate variability (HRV).

METHODS

Thirty healthy Muslim men participated in the study. Their electrocardiograms and EEGs were continuously recorded before, during, and after salat practice with a computer-based data acquisition system (MP150, BIOPAC Systems Inc., Camino Goleta, California). Power spectral analysis was conducted to extract the RPα and HRV components.

RESULTS

During salat, a significant increase (p<.05) was observed in the mean RPα in the occipital and parietal regions and in the normalized unit of high-frequency (nuHF) power of HRV (as a parasympathetic index). Meanwhile, the normalized unit of low-frequency (nuLF) power and LF/HF of HRV (as sympathetic indices) decreased according to HRV analyses. RPα showed a significant positive correlation in the occipital and parietal electrodes with nuHF and significant negative correlations with nuLF and LF/HF.

CONCLUSIONS

During salat, parasympathetic activity increased and sympathetic activity decreased. Therefore, regular salat practices may help promote relaxation, minimize anxiety, and reduce cardiovascular risk.

Alpha neurofeedback improves the maintaining ability of alpha activity

The effects of alpha-neurofeedback (ANF) on electroencephalographic alpha-activity were investigated. Each session consisted of a 2.5-min eye-opened state and 17.5-min of ANF, which was divided into 16 1.25-min bins. Alpha amplitudes were gradually increased as the session was repeated. The maximum value at the start of ANF gradually decreased as time passed, but the slowdown of alpha-activity during each session was decreased as the session was repeated. The correlation between alpha-activity at the end of ANF and at the following session's eye-opened state was highly significant. These results showed that ANF enhances the ability of alpha-activity to maintain itself rather than the increase of alpha-amplitude during intrasession and that the maintained alpha-activity during former training remained until the next session.

Meditation states and traits: EEG, ERP, and neuroimaging studies

Neuroelectric and imaging studies of meditation are reviewed. Electroencephalographic measures indicate an overall slowing subsequent to meditation, with theta and alpha activation related to proficiency of practice. Sensory evoked potential assessment of concentrative meditation yields amplitude and latency changes for some components and practices. Cognitive event-related potential evaluation of meditation implies that practice changes attentional allocation. Neuroimaging studies indicate increased regional cerebral blood flow measures during meditation. Taken together, meditation appears to reflect changes in anterior cingulate cortex and dorsolateral prefrontal areas. Neurophysiological meditative state and trait effects are variable but are beginning to demonstrate consistent outcomes for research and clinical applications. Psychological and clinical effects of meditation are summarized, integrated, and discussed with respect to neuroimaging data.

Validating the efficacy of neurofeedback for optimising performance

The field of neurofeedback training has largely proceeded without validation. Here we review our studies directed at validating SMR, beta and alpha-theta protocols for improving attention, memory, mood and music and dance performance in healthy participants. Important benefits were demonstrable with cognitive and neurophysiological measures which were predicted on the basis of regression models of learning. These are initial steps in providing a much needed scientific basis to neurofeedback, but much remains to be done.

EEG responses to long-term audio-visual stimulation

In this study, linear and nonlinear electroencephalogram (EEG) changes due to long-term audio-visual stimulation (AVS) were investigated. In the course of 2 months, 25 repetitions of a 20-min AVS program with stimulation frequencies in the range 2-18 Hz were applied to six healthy volunteers. EEG data were recorded from six head locations during relaxed wakefulness prior to AVS. Then linear spectral measures (total power, frequency band powers, spectral edge frequency, and spectral entropy), nonlinear measures of complexity (histogram-based entropy and correlation dimension), interdependency measures (linear correlation coefficient, mutual information, and coherence), and measures of subjective assessment were estimated. Evolution of these measures during the whole experiment period was analyzed with respect to the significance of their linear regression. Our results confirm that repetitive training with audio-visual stimulation does induce changes in the electro-cortical activity of the brain. Long-term AVS significantly increased power in theta-1, theta-2, and alpha-1 bands in the frontal and central cortex locations. Total power increased in the right central region. Interhemispheric coherence in alpha-1 band displayed a significant increase between frontal parts in contrast to the decrease of both linear correlation and mutual information. Correlation dimension significantly decreased in some locations while entropy displayed an ascending trend.

Regulation of mental states and biofeedback techniques: effects on breathing pattern

The purpose of the present study was to examine whether breathing pattern may be used as a reliable index for the effectiveness of techniques applied for the regulation of mental states. Heart rate (HR), breathing pattern, galvanic skin response (GSR), and electromyogram (EMG) of the frontalis muscle were measured in 39 male and female subjects aged 18-25 years during 10-minute treatment with relaxation technique (autogenic training and/or music) followed by 10 minutes of imagery training. In the first 7 sessions biofeedback (BFB) was not included, while during the last 6 sessions BFB was introduced and utilized by the subjects. Relaxation (music or autogenic training) led to a decrease in breathing frequency, attributed to lengthening of expiration time, as well as reduced HR, GSR, and frontalis EMG response. In most instances imagery training was related to an increase in these indices. Specifically, significant tachypnea was observed during imagery of sprint running. In most cases BFB substantially augmented the physiological responses. In conclusion, our data suggest that, compared with HR, GSR, and EMG responses, the breathing pattern is at least as sensitive to the mental techniques employed, and may be useful as a psychophysiological index for diagnosis and testing, especially in sport practice.

Human EEG, behavioral stillness and biofeedback

This theoretical synthesis affirms that the normal human EEG is: (1) an indicator of movements of behavior; (2) an undifferentiated indicator of cortical work; but (3) not an indicator of mental processes. A majority of cortical work for an awake person is the mobilization and regulation of all the processes involved in the production, control and prediction of movements of behavior. Abundant synchronous slow waves (alpha, mu, sensory-motor rhythm) indicate a demobilization of voluntary and reflexive, phasic neuromuscular processes which predict, initiate, regulate, and terminate voluntary behavior and movement with a corresponding reduction of afferent feedback associated with sensory data capture, sensory motor integration and behavior. Cortical theta in association with drowsiness indicates that there is further demobilization of reflexive, synergistic, neuromuscular process (as for gait, defensive responses, anti-gravity support), and a reduction of tonic processes which maintain muscle tone or tension with concomitant further reduction of afferent feedback. These various states of behavioral stillness are the catalyst of beneficial psychological and behavioral processes which have been observed to follow biofeedback training to increase synchronous EEG rhythms, and may provide a therapeutic context for psychotherapeutic interventions.

Electroencephalographic correlates of marihuana-induced euphoria

The present study was conducted to determine if there is a neurophysiological correlate of marihuana-induced good effects or euphoria. Three groups of 6 male occasional marihuana smokers were prepared for electroencephalographic (EEG) recording and smoked either placebo or marihuana cigarettes containing 1.26% or 2.53% delta 9-tetrahydrocannabinol (delta 9-THC) in a controlled laboratory setting. Using a continuously available non-verbal joystick device and a questionnaire, subjects reported changes in their subjective mood state while EEG activity was continuously recorded. Subjects reported multiple episodes of intense good effects or euphoria during the first 15 min after marihuana. These episodes of euphoria occurred while plasma delta 9-THC levels were rapidly rising. EEG alpha power during these discrete episodes of euphoria was significantly higher suggesting that these transient EEG changes may reflect a neurophysiological correlate of the reinforcing effects of marihuana.

Stress management techniques: are they all equivalent, or do they have specific effects?

This article evaluates the hypothesis that various stress management techniques have specific effects. Studies comparing various techniques are reviewed, as well as previous literature reviews evaluating the effects of individual techniques. There is evidence that cognitively oriented methods have specific cognitive effects, that specific autonomic effects result from autonomically oriented methods, and that specific muscular effects are produced by muscularly oriented methods. Muscle relaxation and/or EMG biofeedback have greater muscular effects and smaller autonomic effects than finger temperature biofeedback and/or autogenic training. EMG biofeedback produces greater effects on particular muscular groups than progressive relaxation, and thermal biofeedback has greater finger temperature effects than autogenic training. Disorders with a predominant muscular component (e.g., tension headaches) are treated more effectively by muscularly oriented methods, while disorders in which autonomic dysfunction predominates (e.g., hypertension, migraine headaches) are more effectively treated by techniques with a strong autonomic component. Anxiety and phobias tend to be most effectively treated by methods with both strong cognitive and behavioral components.

Effects of alcohol on the EEG in Asian men with genetic variations of ALDH2

Approximately 50% of Asians experience a facial flush following alcohol ingestion. These individuals have an inactive form of mitochondrial aldehyde dehydrogenase (ALDH) encoded by the ALDH2*2 allele. This study matched 15 flushing and 15 nonflushing Asian men on demographics and drinking histories. The 30 subjects were genotyped for ALDH2 and were evaluated both before and following placebo and 0.75 ml/kg alcohol. The two groups did not differ significantly on blood alcohol concentrations after drinking, but did differ in electroencephalographic (EEG) response on the falling phase of the blood alcohol curve. Nonflushing subjects displayed significant increases in slow-alpha EEG activity (7.5-9.0 Hz) at 90 and 150 min post-alcohol consumption, compared to flushing subjects who did not show characteristic increases in this frequency band at these timepoints. These data suggest flushers, those with at least one ALDH2*2 allele, have less of slow-alpha wave EEG response to alcohol than nonflushers with ALDH2*1/2*1 genotype.

Alpha-theta brainwave training and beta-endorphin levels in alcoholics

An alpha-theta brainwave biofeedfack training program was applied as a novel treatment technique for chronic alcoholics. Following a temperature biofeedback pretraining phase, experimental subjects completed 15 30-min sessions of alpha-theta biofeedback training. Compared to a nonalcoholic control group and a traditionally treated alcoholic control group, alcoholics receiving brainwave training (BWT) showed significant increases in percentages of EEG record in alpha and theta rhythms, and increased alpha rhythm amplitudes. Alcoholics receiving BWT showed a gradual increase in alpha and theta brain rhythms across the 15 experimental sessions. These experimentally treated alcoholics showed sharp reductions in self-assessed depression (Beck's Depression Inventory) compared to the control groups. Alcoholics receiving standard medical treatment (abstinence, group psychotherapy, antidepressants) showed a significant elevation in serum beta-endorphin levels at the conclusion of the experiment. This neuropeptide is an index of stress and a stimulant of caloric (e.g., ethanol) intake. Application of brainwave treatment, a relaxation therapy, appears to counteract the increase in circulating beta-endorphin levels seen in the control group of alcoholics. 13-month follow-up data indicate sustained prevention of relapse in alcoholics that completed alpha-theta brainwave training.

Electroencephalographic activity and plasma ACTH during ethanol-induced euphoria

Covariance of brain electrical activity (EEG), plasma adrenocorticotrophic hormone (ACTH) and cortisol levels, and mood states were determined for healthy adult men during the first 2 hr after ingestion of ethanol or ethanol placebo under controlled double-blind conditions. Analysis of integrated plasma ACTH and cortisol levels at 5-min intervals, EEG power spectral analysis during consecutive 2-min epochs, and continuous assessment of mood states with a nonverbal instrumental device were carried out during the ascending phase of the blood ethanol curve. Ethanol induced rapid changes in brain electrical activity and plasma ACTH levels that were significantly correlated with subjective perception of changes in mood. The paroxysmal short epochs of euphoria associated with electroencephalographic and ACTH responses during the ascending phase of the blood ethanol curve may reflect physiological concomitants of pharmacological and behavioral reinforcers that enhance risk for perpetuation of drinking and alcohol abuse.

Alpha enhancement: a comparison study of biofeedback, open focus training, and control procedures

Alpha wave production has been related to affective and physiological arousal states since Berger's (1929) initial research. More recently, the possibility of subjects' control of alpha production has been investigated via the innovation of biofeedback procedures. Research conducted by Kamiya in the 1960s and others led to the early conclusion that alpha-wave production could be controlled and that such control could facilitate enhancement of a person's state of physical and psychological well-being. Subsequent research data have questioned these conclusions. The present study focused upon alpha-wave production with or without a procedure for relaxation called "open-focus training." Twenty subjects were divided into four equal groups and seen for three 20-min. sessions. Results suggested a deterioration of alpha production with all groups combined, no significant differences between the biofeedback and no biofeedback control groups (without "open-focus training"), and greater decrease in alpha production during each session in the "open-focus" groups (with or without biofeedback). These unusual results and their implications are discussed.

The effects of visual feedback on hemispheric alpha asymmetries and reported processing strategies: a single-subject experimental design

A double reversal single-subject experimental design was used to study the effects of visual feedback on the hemispheric alpha asymmetries of a male subject during a linguistic task. Results indicated that the subject demonstrated flexibility in hemispheric alpha and corresponding processing strategies employed when an alpha biofeedback procedure was used. These results provide further support for the notion that right and left hemispheric activation is associated with different, yet compatible, cognitive strategies and that both can be manipulated under conditions of feedback.

Alpha enhancement, autonomic activation, and extraversion

Autonomic activation as reflected by heart rate, skin conductance, muscle tension, and T-wave amplitude of the electrocardiogram were registered during biofeedback training of EEG alpha. The group of 25 subjects showed significant enhancement of alpha but no systematic change in autonomic activation. This result was interpreted as supporting Eysenck's theory of two feedback loops for mediating cortical arousal. According to this theory, autonomic changes would not be expected to accompany changes in cortical arousal during resting conditions lacking emotional content and, therefore, not involving the visceral brain. Although some of the subjects who succeeded in increasing alpha experienced it as positive and others as strenuous, alpha change did not correlate significantly either with the dimension of extraversion, or with those of locus of control and neuroticism.

Toward a psychophysiology of waking fantasy: EEG studies

EEG investigations into the psychophysiology of waking fantasy have yielded interesting but inconclusive results. The most promising lines of research are reviewed with particular reference to the methodological complexities involved. Studies of alpha blocking, alpha states, theta states, and cerebral asymmetries are described. Comparisons are drawn between these lines of investigation and the methods of experimental dream research.

Distribution of 'criterion' alpha in the resting EEG: further argument against the use of an amplitude threshold in alpha biofeedback training

The object of this study was to explore the relevance of an amplitude threshold for defining alpha in biofeedback studies. One of the lowest thresholds used in earlier studies (1.5 microV) was selected and the EEG base level of 94 subjects measured. Due to the importance of reinforcement rate in biofeedback, results were divided into three categories: under 25%, between 26-74%, and over 75% alpha. The results showed a positively skewed distribution with 68% of the subjects displaying under 25% alpha. The subjects' means on the control variables: anxiety, impulsivity, and monotony avoidance were within the range of normal and did not correlate with the amplitude categories. The conclusion drawn was that skewness is not the result of an abnormal sample but of an arbitrarily set amplitude criterion. On the basis of this data, an integrated alpha amplitude measure is advocated.

Effectiveness of alpha biofeedback therapy: negative results

Assessed the utility of alpha biofeedback training in the treatment of psychiatric patients (N = 66). Biofeedback and placebo biofeedback groups were given alpha or mock-alpha training sessions, and their improvement on 54 variables was compared to that of no-treatment controls. Only a chance number of significant differential changes appeared among the three groups. A comparison of these negative results with an earlier study from our laboratory that had yielded positive findings suggested that clinical improvement in alpha biofeedback treatment may be the result of the relaxation training or special verbal instructions often incorporated into alpha training.

Feedback control of human alpha rhythm from the central area

Twenty subjects, aged 17 to 25, were given from 5 to 10 sessions of training in controlling alpha. They were divided into three groups, respectively reinforced for increasing alpha from the central area, reinforced for decreasing alpha from the central area, and given noncontingent reinforcement. Compared with the initial baseline, the alpha of the noncontingent subjects did not change, while those reinforced for increases were reliably higher and those reinforced for decreases reliably lower than the noncontingent group. A slight trend toward improvement during successive sessions was not reliable. Since the experiment was conducted in the Soviet Union, the subjects had no expectations of an "alpha experience." Although tests showed a slight elevation in mood at the end of the sessions, there were no differences among the groups. There was an increase in reports of fatigue after the training sessions. There were no reports of using visual or somatomotor maneuvers as a means of controlling alpha. Furthermore, alpha rhythm control was not found to be consistently correlated with changes in heart rate, respiration, or mood, as determined by cross-correlation analysis.

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.

EEG feedback training: enhancement of somatosensory cortical activity

The mu rhythm is a spontaneous electroencephalographic pattern which can be recorded over human somatosensory cortex in the absence of movement. Power spectral analysis across 50 sessions of EEG feedback training showed that mu activity could be systematically enhanced, whereas the 12--14 c/sec component of low voltage fast activity could not be modified. Results indicate that long-term modification of at least one normal cortical rhythm, initially present in the human EEG, is possible with feedback training but that training cannot produce such a rhythm.

Alpha biofeedback therapy in alcoholics: an 18-month follow-up

In an earlier study on patients with alcohol problems, an experimental group given 10 hour-long alpha biofeedback training sessions showed greater improvement on State and Trait Anxiety scores than did a control sample. In the present study an 18-month follow-up was done on those Ss. The differences between the experimentals and controls in State and Trait Anxiety after 18 months were essentially identical to the differences between them immediately after treatment, which indicates that alpha training had long-range therapeutic effects. A difference between the groups on the Alcohol Rehabilitation Followup Questionnaire also suggested that alpha training may have been associated with some reduction in alcohol consumption as well.

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.