Portable wireless neurofeedback system of EEG alpha rhythm enhances memory

Background

Effect of neurofeedback training (NFT) on enhancement of cognitive function or amelioration of clinical symptoms is inconclusive. The trainability of brain rhythm using a neurofeedback system is uncertainty because various experimental designs are used in previous studies. The current study aimed to develop a portable wireless NFT system for alpha rhythm and to validate effect of the NFT system on memory with a sham-controlled group.

Methods

The proposed system contained an EEG signal analysis device and a smartphone with wireless Bluetooth low-energy technology. Instantaneous 1-s EEG power and contiguous 5-min EEG power throughout the training were developed as feedback information. The training performance and its progression were kept to boost usability of our device. Participants were blinded and randomly assigned into either the control group receiving random 4-Hz power or Alpha group receiving 8–12-Hz power. Working memory and episodic memory were assessed by the backward digital span task and word-pair task, respectively.

Results

The portable neurofeedback system had advantages of a tiny size and long-term recording and demonstrated trainability of alpha rhythm in terms of significant increase of power and duration of 8–12 Hz. Moreover, accuracies of the backward digital span task and word-pair task showed significant enhancement in the Alpha group after training compared to the control group.

Conclusions

Our tiny portable device demonstrated success trainability of alpha rhythm and enhanced two kinds of memories. The present study suggest that the portable neurofeedback system provides an alternative intervention for memory enhancement.

     

The Effects of Individual Upper Alpha Neurofeedback in ADHD: An Open-Label Pilot Study

Standardized neurofeedback (NF) protocols have been extensively evaluated in attention-deficit/hyperactivity disorder (ADHD). However, such protocols do not account for the large EEG heterogeneity in ADHD. Thus, individualized approaches have been suggested to improve the clinical outcome. In this direction, an open-label pilot study was designed to evaluate a NF protocol of relative upper alpha power enhancement in fronto-central sites. Upper alpha band was individually determined using the alpha peak frequency as an anchor point. 20 ADHD children underwent 18 training sessions. Clinical and neurophysiological variables were measured pre- and post-training. EEG was recorded pre- and post-training, and pre- and post-training trials within each session, in both eyes closed resting state and eyes open task-related activity. A power EEG analysis assessed long-term and within-session effects, in the trained parameter and in all the sensors in the (1–30) Hz spectral range. Learning curves over sessions were assessed as well. Parents rated a clinical improvement in children regarding inattention and hyperactivity/impulsivity. Neurophysiological tests showed an improvement in working memory, concentration and impulsivity (decreased number of commission errors in a continuous performance test). Relative and absolute upper alpha power showed long-term enhancement in task-related activity, and a positive learning curve over sessions. The analysis of within-session effects showed a power decrease (“rebound” effect) in task-related activity, with no significant effects during training trials. We conclude that the enhancement of the individual upper alpha power is effective in improving several measures of clinical outcome and cognitive performance in ADHD. This is the first NF study evaluating such a protocol in ADHD. A controlled evaluation seems warranted due to the positive results obtained in the current study.     

EMG and EEG biofeedback training in the treatment of a 10-year-old hyperactive boy with a developmental reading disorder

The serial application of electromyographic (EMG) and sensorimotor (SMR) biofeedback training was attempted with a 10-year-old boy presenting a triad of symptoms: an attention deficit disorder with hyperactivity, developmental reading disorder, and ocular instability. Symptom elimination was achieved, for all three aspects of the triad, following the procedure of first conditioning a decrease in EMG-monitored muscle tension and then conditioning increases in the amplitude of sensorimotor rhythm over the Rolandic cortex. The learned reduction of monitored EMG levels was accompanied by a reduction in the child's motoric activity level to below that which had been achieved by past administration of Ritalin. In addition, the attention deficit disorder with hyperactivity was no longer diagnosable following the EMG biofeedback training. The learned increase in the amplitude of monitored SMR was accompanied by remediation of the developmental reading disorder and the ocular instability. These results remained unchanged, as ascertained by follow-ups conducted over a 24-month period subsequent to the termination of biofeedback training.     

Comment on feedback training of parietal-occipital alpha asymmetry in normal human subjects

Experiments with feedback regulation of normal subjects' parietal-occipital alpha electroencephalographic asymmetry have shown that subjects learned to optimize the conditions under which symmetry and asymmetry occurred. Asymmetry was defined as the difference in the occurrence of the two hemispheres' alpha EEG activity. The results of this experiment can be interpreted to mean that the subjects did not learn alpha asymmetry per se, but instead learned to increase then percent time of alpha and increase the alternations between alpha and no alpha. This condition is optimized when the subject has his eyes closed and is not performing a visual search. On the other hand, symmetry is optimized when the subject performs a visual task. Methodological problems in feedback training are discussed.     

Effect of feedback contingencies on the control of occipital alpha

Ten color transparencies were presented 30 times each to ten normal adults in response to changes in their occipital-parietal EEG's. By means of a feedback paradigm, detected alphas caused each slide to flash and stay on as long as alpha persisted, and then to turn off when alpha attenuated, according to four different contingency conditions. For half of the feedback trials, stimulus presentation depended on alpha detection in only one hemisphere and was not influenced by changes in the simultaneously recorded contralateral EEG. For the other feedback trials, stimulus presentation was bilaterally contingent. These contingency configurations were compared with sham feedback, a noncontingent condition during which slide presentation was controlled by a prerecorded tape. For both alpha and no-alpha, the ratio of mean duration over standard error was used as a quantification of the EEG response to visual stimulation. It was assumed that larger ratios indicated increased control of the EEG. Compared with the sham condition, all feedback contingencies produced greater ratios, and hence, improved control of the EEG. The highest ratios were obtained during unilateral feedback from the EEG in which the occurrence of alpha elicited the visual stimulus. The results show that contingency between a visual stimulus and the EEG is an important parameter with regard to experimental control of the EEG.     

Increasing Performance of Professional Soccer Players and Elite Track and Field Athletes with Peak Performance Training and Biofeedback: A Pilot Study

The aim of this pilot study was to investigate the effects of an intervention consisting of mental coaching combined with either electro encephalogram (EEG) alpha power feedback or heart rate variability (HRV) feedback on HRV, EEG outcomes and self-reported factors related to stress, performance, recovery and sleep quality in elite athletes. A prospective pilot study was performed with two distinct cohorts. Soccer players were provided with four sessions of mental coaching combined with daily HRV biofeedback (Group A); track and field athletes were provided with four sessions of mental coaching in combination with daily neurofeedback (Group B). Measurements were performed at baseline, post intervention and at 5 weeks follow-up. Objective measures: EEG and ECG. Subjective measures: Numeric Rating Scale for performance, Pittsburgh Sleep Quality Index, Rest and Stress Questionnaire and Sports Improvement-60. Group characteristics were too distinct to compare the interventions. Linear mixed models were used to analyze differences within groups over time. In Group A, significant changes over time were present in alpha power at 5 of 7 EEG locations (p < 0.01–0.03). LF/HF ratio significantly increased (p = 0.02) and the concentration (p = 0.02) and emotional scale (p = 0.03) of the SIM-60 increased significantly (p = 0.04). In Group B, the HRV low frequency power and recovery scale of the REST-Q significantly increased (p = 0.02 and <0.01 resp.). Other measures remained stable or improved non-significantly. A mental coaching program combined with either HRV or EEG alpha power feedback may increase HRV and alpha power and may lead to better performance-related outcomes and stress reduction. Further research is needed to elucidate the effects of either type of feedback and to compare effects with a control group.     

EEG Activity in the Process of Measuring-off of Time Intervals by Humans

We recorded EEG from sites C3 and C4 in an experimental situation with internal counting-off of a 20-sec-long time interval, whose beginning and end were limited by the tested subject by pushing a button; 65 adult men and women took part in the tests. In the first experimental series, the subject obtained no real information on the accuracy in production of the interval. In the second series, such information was displayed by feedback visual signals. We calculated means of the measured intervals ( ), coefficient of variation of the realizations (CV), and, in the series with the real feedback, successfulness of measuring-off (normalized number of fits within an acceptable range of the standard interval, 19 to 21 sec). Analysis of the data obtained in the first experimental series for the entire tested group demonstrated the existence of a reverse dependence between the modal frequency of EEG beta rhythm recorded from the left hemisphere in the course of measuring-off of the interval and the value. In the second series, we found significant negative correlation between the beta rhythm power in both hemispheres and CV, that between the alpha rhythm power in the left hemisphere and , and positive correlation between the alpha rhythm frequency in the left hemisphere and successfulness of the interval counting-off. Analysis of the dynamics of EEG of each tested subject demonstrated the existence of mostly reverse dependences between the powers of a few EEG rhythms and duration of the produced interval. We hypothesize that the frequencies of the alpha and beta EEG oscillations play the role of significant indices reflecting the speed of the internal clock of the individual. We also emphasize the complex nature and the high individual variability of the EEG pattern in the course of measuring-off of time intervals.     

A New Method for Self-Regulation of Slow Cortical Potentials in a Timed Paradigm

A new method of slow cortical potential (SCP) biofeedback is described, in which subjects were presented with a sequence of two alternating tones. Subjects learned to adjust their SCPs with the 4-s rhythm of presented tones by producing directed SCP changes only in certain inter-tone intervals. Specifically, they learned to simultaneously produce two EEG signals: 1) positive or negative SCP shift at vertex, and 2) SCP asymmetry between the right and the left central area. After one training session, 13 healthy participants were able to differentiate significantly between the negativity and the positivity conditions; this differentiation was achieved within less than 300 ms after the discriminative signal, i.e. much faster than in previous studies employing traditional SCP biofeedback technique. However, these participants did not produce a significant hemispheric asymmetry in the first session. In the second experiment, five subjects participated in prolonged training (6 to 17 sessions). Highly significant control of SCP asymmetry over the precentral cortex was attained in four out of five participants. Advantages and disadvantages of the new method as compared with the classical SCP biofeedback technique are discussed.     

Feedback delay and amplitude threshold and control of the occipital EEG

Six normal adults looked at 12 color transparencies that were presented 30 times each in response to the occurrence of alpha in the occipital EEG and that were not presented when no-alpha occurred. The time delay between the occurrence of recorded EEG alpha and the feedback stimulus was systematically varied, as was the threshold value of alpha amplitude required for feedback stimulus to occur. As time delay increased, the replicative reliability of the temporal association between alpha and the visual stimulus decreased. The measures of the EEG response were: the mean durations of alpha and of no-alpha durations ; an estimate of random scatter or variability in a single trial (S _e ); and the ratio of these , which is the reciprocal of the coefficient of variation. The latter ratio defines control of the EEG response. Control was greatest for the minimum feedback delay (.25 sec) and a feedback threshold of 25% of the maximum peak alpha amplitude recorded under a prior eyes-closed. resting condition. Control of the EEG decreased as time delays increased and at lower and higher feedback thresholds. It was proposed that the measurement of control for various combinations of values of relevant experimental parameters could be used to select that combination which gave the best control. This optimum combination of values of parameters could be chosen for astandardized method.This research was supported in its entirety by the Veterans Administration Medical Research Program.     

Concordance among self-regulated responses: Is self-regulatory ability a psychophysiological “trait”?

The purposes of this study were to examine whether or not self-regulation of physiological responses demonstrates day-to-day reliability, to determine the degree of individual subject consistency (or concordance) in the ability to self-regulate across several different physiological responses, and, finally, to explore the impact of biofeedback training on interresponse concordance. Twenty normal subjects participated in six bidirectional self-regulation sessions—the first and last sessions involving instructions only, and the remainder, biofeedback. Self-regulation scores consisted of the absolute difference between increase and decrease trial means. The average test-retest reliability coefficients (r _s) for the self-regulation scores, across the four biofeedback sessions, were a highly significant .50, .68, .30, and .47 for EEG, EMG, HR, and SCL, respectively. By contrast, the average concordance among the self-regulation scores for the four feedback sessions, estimated by Kendall's coefficient of concordance, was a marginally significant 39% of the possible variance of the rank sums. This corresponds to an average between-responser _s value only of .19. The concordance level from the initial no-feedback (i.e., instructions only) session was not significant. Multivariate concordance levels did increase during the first three feedback sessions, but declined at the fourth, and again was nonsignificant during the final no-feedback session. Among the individual self-regulation response pairings, only the EEG/EMG combination was consistently associated during the no-feedback sessions. The present results suggest that self-regulatory ability is neither a highly unitary “trait”-like phenomenon nor an entirely response-specific event, but may vary considerably as a function of subject factors, or the situational circumstances, under which it is measured.     

Correction of functional disturbances during pregnancy by the method of adaptive EEG biofeedback training

The applicability and efficiency of the electroencephalogram (EEG)-based method of biofeedback (BFB) training in correcting functional disorders in pregnancy have been evaluated in an obstetric/gynecological clinic in 65 pregnant women. Each of them took part in 2–12 examinations, which differed in voluntarily regulated EEG rhythm (a decrease in the θ, an increase in the α, or a decrease in the β rhythm), left-or right-hemispheric location of the EEG derivations, and the duration of the delay (3 or 30 s) of auditory feedback stimuli. As compared to the baseline, the most distinct and significant changes were observed in the α and θ rhythms during medical procedures, testifying to a general relaxing effect of the EEG BFB. The greatest number of successful trials (83.3 ± 4.4%) was observed for the BFB sessions aimed at decreasing the θ activity, and the lowest number (32.0 ± 6.7%), for the attempts at decreasing the EEG β rhythm. Voluntary control of the α rhythm of the EEG yielded a moderate number of successful trials (63.7 ± 5.3%), but it was characterized by the lowest efficiency (demonstrating minimal differences in positive changes in the functional state between successful and unsuccessful trials). The comparatively low effectiveness of voluntary BFB control of the α rhythm may have been determined by its high heterogeneity and suggests the necessity of using more narrowband EEG components in BFB sessions.     

Rhythmic changes in ribonuclease activity in relation to nucleic acid synthesis in cotyledons ofChenopodium rubrum L. and to floral induction of the plants

Ribonuclease (RNAse) activity was investigated in cotyledons ofChenopodium rubrum plants subjected to various conditions of illumination (photoperiodic induction, continuous light, induction cancelled by interrupting the dark period by a light-break). At the end of the dark period of the single inductive cycles RNAse activity of induced plants was inferior to that of plants grown in continuous light. At the end of the first two cycles the activity was lowest after the interruption of the dark period by light. The investigation of the enzyme in 6h intervals showed rhythmic changes in activity to occur in induced plants. Enzyme activity followed a pattern opposed to this of nucleic acid (NA) synthesis in the cotyledons. In plants from continuous light the enzyme activity did not show any rhythm and in plants having obtained a light-break during the inductive period the rhythm was less distinct than in the induced ones. The period length of the endogenous rhythm of NA synthesis in the cotyledons is about half as long as this of flowering and the peaks of flowering coincide with the throughs of NA synthesis.     

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.The assistance of Eric Peper, Sylvia Runnals, Rosemary Billingslea, and Thomas McLaughlin in the EEG recording and data analysis was indispensible to this study.     

Moderation of Increased Anxiety in Children and Teenagers with the Use of Neurotherapy: Estimation of the Efficacy

We estimated the efficacy of using the technique of feedback (FB) by EEG characteristics (EEG-FB, neurotherapy) with the aim of reducing increased anxiety levels in healthy 10- to 14-year-old children. The anxiety level was estimated using the Prikhojan anxiety test, the Spielberger–Khanin questionnaire, and the House–Tree–Person projective drawing technique. Positive effects of series of neurotherapy sessions were obvious. After training was completed, we observed significant increases in the ratios of the amplitudes of alpha and theta rhythms, semsorimotor and theta rhythms, as well as of the modal frequency of the EEG alpha rhythm in tested persons of the experimental group (n = 7). In the control group (n = 10), changes in these values did not reach the significance level. In the experimental group of tested persons subjected to EEG-FB sessions, the anxiety level decreased appreciably; in addition, the indices “feeling of inferiority” and “frustration” decreased significantly. In the control group, alterations of these psychological indices were not unidirectional. Therefore, modifications of the EEG pattern, which occurred in the course of training and were accompanied by a decrease in the anxiety level in the experimental group, can be indicative of the expediency of EEG-FB for the reduction of high anxiety levels in children and teenagers.     

Hyperactivity and sensation seeking as autoregulatory attempts to stabilize brain arousal in ADHD and mania?

Hypoarousal as indicated by skin conductance and electroencephalography (EEG) has been discussed as a pathogenetic factor in attention-deficit/hyperactivity disorder (ADHD). The aim of this paper was to review these arousal-related pathogenetic concepts and to present the more recently proposed vigilance regulation model of affective disorders and ADHD. The latter builds on methodological advances in classifying short EEG segments into vigilance stages (Vigilance Algorithm Leipzig, VIGALL), indicating different states of global brain function (“brain arousal”). VIGALL allows the objective assessment of vigilance regulation under defined conditions, e.g. how fast vigilance declines to lower vigilance stages associated with drowsiness during 15–20-min EEG recordings under resting conditions with eyes closed. According to the vigilance regulation model, the hyperactivity and sensation seeking observed in overtired children, ADHD and mania may be interpreted as an autoregulatory attempt to create a stimulating environment in order to stabilize vigilance. The unstable regulation of vigilance observed in both mania and ADHD may thus explain the attention deficits, which become especially prominent in monotonous sustained attention tasks. Among the arguments supporting the vigilance regulation model are the facts that destabilizing vigilance (e.g. via sleep deprivation) can trigger or exacerbate symptoms of ADHD or mania, whereas stabilizing vigilance (e.g. via psychostimulants, reducing sleep deficits) alleviates these symptoms. The potential antimanic effects of methylphenidate are presently being studied in an international randomized controlled trial. We propose vigilance regulation as a converging biomarker, which could be useful for identifying treatment responders to psychostimulants and forming pathophysiologically more homogeneous ADHD subgroups for research purposes.     

Problems in heart rate and alpha electroencephalographic feedback

When a subject has demonstrated successful control over a feedback stimulus, the experimenter should not interpret this to mean that the subject has learned a specific correlated physiological function. Data from two types of experiments — attempted heart rate stoppage and alpha electro-encephalographic feedback control — demonstrate some of the problems. The apparent heart stoppage of one subject was caused by the decrease in arterial pressure which occurred during a Valsalva procedure. The successful control over feedback stimuli during an EEG feedback study led to confused results: in this case the alpha criterion was too broad and was satisfied by different alpha frequencies, amplitudes, phase relations, and toposcopic distributions. Grouped subject data would only confuse the interpretation further. Suggestions to avoid some EEG feedback pitfalls are given.     

脑电生物反馈系统的研制和脑电α成分反馈的研究

本文介绍了我们研制的微机化脑电反馈系统.并报告了我们所进行的正常人脑电α成分生物反馈训练实验,证明了脑电生物反馈提升α成分比例的可行性.本文还论讨了国际上现行关于脑电α成分生物反馈研究中存在的问题,提出了有效的解决方法.     

EEG activation response under different neurohumoral states

In order to determine under which neurohumoral conditions the response to usual opening of the eyes stimulates the Berger effect, the electroencephalographic, electrocardiographic, and electromyographic responses to eyes opening have been recorded simultaneously with the psychometric indices of emotional tension and cognitive performance in 59 healthy women aged 18–27 years every two or three days during one or two menstrual cycles determined according the progesterone level in the morning. For excluding the influence of the Novelty factor, the monitoring began at the menstrual phase of the cycle in 29 women and at the luteal phase in the other 30 women. A single examination has been performed in a separate group of 30 women to study the relationship of these parameters with the current progesterone and cortisol levels in saliva. Two-factor ANOVA has shown that the magnitude of amplitude suppression and the bandwidth of the low-frequency α EEG range in the follicular phase of the menstrual cycle are greater than in the luteal one and depend on the Novelty factor. The indices of the Berger effect of the upper-frequency α range do not depend on the neurohumoral state or the Novelty factor. The amplitude suppression and the bandwidth of the lowfrequency α range alone are predictors of the activation in the response to eyes opening because the changes are unidirectional and are interrelated with the autonomic and hormonal characteristics of the activation. It has been demonstrated that eyes opening is a stimulus for the activation only in the neurohumoral state corresponding to the follicular phase of the menstrual cycle. This study has established the dependence of the central and autonomic activation on the individual α frequency EEG profile and the neurohumoral state.