Applied Psychophysiology and Biofeedback

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Article
Pulse rate variability is a physiological parameter that has been extensively studied and correlated with many physical ailments. However, the phase relationship between inter-beat interval, IBI, and breathing has very rarely been studied. Develop a technique by which the phase relationship between IBI and breathing can be accurately and efficiently extracted from photoplethysmography (PPG) data. A program based on Lock-in Amplifier technology was written in Python to implement a novel technique, Dynamic Phase Extraction. It was tested using a breath pacer and a PPG sensor on 6 subjects who followed a breath pacer at varied breathing rates. The data were then analyzed using both traditional methods and the novel technique (Dynamic Phase Extraction) utilizing a breath pacer. Pulse data was extracted using a PPG sensor. Dynamic Phase Extraction (DPE) gave the magnitudes of the variation in IBI associated with breathing (ΔIBI) measured with photoplethysmography during paced breathing (with premature ventricular contractions, abnormal arrhythmias, and other artifacts edited out). ΔIBI correlated well with two standard measures of pulse rate variability: the Standard Deviation of the inter-beat interval (SDNN) (ρ = 0.911) and with the integrated value of the Power Spectral Density between 0.04 and 0.15 Hz (Low Frequency Power or LF Power) (ρ = 0.885). These correlations were comparable to the correlation between the SDNN and the LF Power (ρ = 0.877). In addition to the magnitude ΔIBI, Dynamic Phase Extraction also gave the phase between the breath pacer and the changes in the inter-beat interval (IBI) due to respiratory sinus arrythmia (RSA), and correlated well with the phase extracted using a Fourier transform (ρ = 0.857). Dynamic Phase Extraction can extract both the phase between the breath pacer and the changes in IBI due to the respiratory sinus arrhythmia component of pulse rate variability (ΔIBI), but is limited by needing a breath pacer.
 
Positive (PA) and negative (NA) affect scores after Cyberball for the participants in the INCLUSION and EXCLUSION groups
Variations of BR (breaths per minute) compared to basal level for the different time intervals (*p < .05; **p < .01)
Article
The emotional reactions to social exclusion can be associated with physiological responses that could allow researchers to estimate the valence and intensity of the ongoing affective state. In this work, respiratory activity was analysed to verify whether breathing rate variations can be considered as predictive factors of subsequent positive and negative affect after inclusion and exclusion in young women. A standard Cyberball task was implemented and manipulated information was provided to the participants to create both conditions. The participants were socially excluded by limiting their participation to 6% of the total number of passes among three teammates and providing negative feedback about them. The results suggest that breathing rate can be a good option to infer subjective feelings during social interactions and a promising feature to incorporate into modern emotion monitoring systems as an alternative to other physiological measures. Furthermore, the interaction between metaemotion and physiology was studied by recording breathing rate while completing the Positive and Negative Affect Schedule, evidencing a breathing rate increase during the emotion self-assessment only after exclusion.
 
ATR in each NFT session across all participants, learners and non-learners. The error bars depict standard error of the mean (SEM)
Number cancellation score in pre-test and post-test
Increase of number cancellation score in learners and non-learners
Scatter plot of NFT learning efficacy and the change of number cancellation score
Article
Attention plays an important role in children’s development and learning, and neurofeedback training (NFT) has been proposed as a promising method to improve attention, mainly in population with attention problems such as attention deficit hyperactivity disorder. However, whether this approach has a positive effect on attention in normal developing children has been rarely investigated. This pilot study conducted ten sessions of alpha/theta ratio (ATR) NFT on eight primary students in school environment, with two to three sessions per week. The results showed inter-individual difference in NFT learning efficacy that was assessed by the slope of ATR over training sessions. In addition, the attention performance was significantly improved after NFT. Importantly, the improvement of attention performance was positively correlated with the NFT learning efficacy. It thus highlighted the need for optimizing ATR NFT protocol for the benefits on attention at the individual level. Future work can employ a double-blind placebo-controlled design with larger sample size to validate the benefits of ATR NFT for attention in normal developing children.
 
EEG Topographical Heat Maps for Theta, Alpha, and Beta Power (µV) across EEG Channels for Pre-Test and Post-Test
Article
We examined whether practice in an open skill video-game task would lead to changes in performance, attention, motivation, perceived effort, and theta, alpha, and beta waves. Specifically, we were interested on whether potential performance gains from practice would be primarily explained by the neural efficiency (i.e., cortical idling) or the neural proficiency hypothesis (i.e., mix of heightened and reduced activation across the cortex). To this end, we asked 16 novice participants (8 males and 8 females; Mage = 23.13 years) to play a Nintendo Wii video-game shooting task, namely Link’s Crossbow Training. Pre-test scores, which were followed by an acquisition phase, were compared to post-test scores. Performance and subjective data were recorded for each trial and EEG data was continuously recorded using the portable EEGO System. Our findings revealed that performance increased while attention decreased at post-test, thereby confirming that practice leads to performance gains and reduces attentional overload. No changes in motivation or perceived effort were observed, perhaps because effort is a gestalt multidimension construct and video-gaming is an inherently motivating activity. EEG frequency analysis revealed that, for the most part, performance gains were accompanied by increased cortical activity across frequencies bands, thus lending primary support to the neural proficiency hypothesis. Accordingly, neurofeedback interventions to aid motor learning should teach performers not only how to silence their brains (i.e., quiescence state linked to automaticity and “flow”) but also how to amplify task-relevant brain networks.
 
Flowchart of study participants (with a focus on psychophysiological variables). n1 Center 1, n2 Center 2; CBT cognitive behavioral therapy, EDA electrodermal activity, HC healthy control, HR heart rate, HRV heart rate variability, SAD social anxiety disorder, TSST-C Trier Social Stress Test for Children; WLC = waitlist control
Procedure
Interbeat interval during first TSST-C comparing SAD and HC group (estimated means and standard errors of the model)
Skin conductance level during first TSST-C comparing SAD and HC group (estimated means and standard errors of the model)
Parasympathetic arousal during first TSST-C comparing SAD and HC group (estimated means and standard errors of the model)
Article
Models of social anxiety disorder (SAD) stress the relevance of physiological arousal. So far, limited research has been conducted in children with SAD in experimental stress designs. Thus, examining autonomic arousal, children with and without SAD completed a standardized social stressor (Trier Social Stress Test for Children-C; TSST-C). Pre-existing differences to healthy controls (HC) were expected to decrease after receiving cognitive behavior therapy (CBT). Children with SAD (n = 64) and HC children (n = 55) completed a TSST-C. Children with SAD participated in a second TSST-C after either cognitive-behavioral treatment or a waitlist-control period (WLC). As expected, children with SAD showed blunted heart rate reactivity compared to HC children. Further, children with SAD had elevated levels of tonic sympathetic arousal as indexed by skin conductance level compared to HC. Children with SAD showed lower parasympathetic arousal during the baseline compared to HC. Children receiving treatment did not differ from children in the WLC condition in a repeated social stress test. Psychophysiological differences between children with SAD and HC children could be confirmed as indicated by previous research. The lack of physiological effects of the intervention as an experimental manipulation might be related to slower changes in physiology compared to e.g. cognition.
 
PRISMA 2020 flow diagram for search in databases and other sources.
Adapted from Page et al. (2021)
Historical evolution by period of years of studies with randomized controlled trials included in this review
Geographic distribution by country of origin of studies with randomized controlled trial design included in this review
Journals that have published at least one randomized controlled trial during the period reviewed
Article
Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent disorders in children and adolescents. Neurofeedback, a nonpharmaceutical treatment, has shown promising results. To review the evidence of efficacy of neurofeedback as a treatment for children and adolescents with ADHD. A systematic review of the specific scientific studies published in 1995–2021, identifying and analyzing randomized controlled trials (RCT). A total of 1636 articles were identified and 165 met inclusion criteria, of which 67 were RCTs. Neurofeedback training was associated with significant long-term reduction in symptoms of ADHD. Though limitations exist regarding conclusions about the specific effects of neurofeedback, the review documents improvements in school, social, and family environments.
 
Example of HRCRmax from each sleep stage of a participant. Each HRCRmax is represented with its heart rhythm pattern and PSD. The left-hand graphs are the IBI tachograms for the individual sleep stages. The right-hand graphs are the PSD plots of the IBI tachograms at left; HRCRmax values are shown in the upper right corner
Article
The psychophysiological coherence model proposes that a heart rhythm pattern, known as heart rhythm coherence (HRC), is associated with dominant parasympathetic activity and the entrainment of respiratory function, blood pressure, and heart rhythms. Although the HRC pattern has primarily been assessed during wakefulness, changes in cardiac and autonomic activity that occur during sleep stages can also be associated with the HRC pattern. The objective of this study was to examine whether any differences in the HRC pattern could be detected among various sleep stages. Eighteen healthy young individuals participated in this study. Two consecutive polysomnographic (PSG) recordings were obtained from each participant, several segments of cardiac activity were obtained from the second PSG. The HRC pattern was quantitatively evaluated by calculating the HRC ratio (HRCR). The highest peaks in the coherence band (Coher-Peak), 0.1-Hz index, respiratory sinus arrhythmia (RSA), and heart rate (HR) were evaluated. A Friedman test showed significant differences among sleep stages in the Coher-Peak, 0.1-Hz index, RSA, and HR; the Coher-Peak and RSA values were lower in rapid eye movement (REM) sleep, while the 0.1-Hz and HR values were higher in REM sleep. Post hoc analyses identified significant differences between the N2 and REM sleep stages. Among the various sleep stages, HR and RSA measurements behaved independently of the HRC pattern, and the HRC pattern did not appear to be associated with the 0.1 Hz frequency. Further studies are required to identify the characteristics of the HRC pattern during sleep.
 
Article
Breathing at the resonance frequency (~ 6 breaths per min) produces resonance effects on baroreflex gain, blood pressure, vascular tone, and therapeutic benefits. Evgeny Vaschillo and Paul Lehrer have emphasized that the stimulation frequency is critical for producing resonance effects in the cardiorespiratory system. Although clinicians overwhelmingly use paced breathing to increase HRV, other promising methods exist. Vaschillo, Lehrer, and colleagues have shown that presenting non-respiratory stimulation at 0.1 Hz—pictures with an emotional valence or rhythmical muscle tensing—amplifies oscillations in heart rate, blood pressure, and vascular tone. Participants in the present study included 49 undergraduate students randomly assigned to one of six different orders of 5-min trials of 1, 6, and 12 muscle contractions per min (cpm), separated by 3-min buffer periods intended to minimize carryover. This randomized controlled trial replicated the Vaschillo et al. (Psychophysiology 48:927–936, 2011. https://doi.org/10.1111/j.1469-8986.2010.01156.x) finding that 6-cpm RSMT can produce a PkFreq of ~ 0.10 Hz, similar to 6-bpm RF breathing. RSMT at 1 and 6 cpm increased five time-domain metrics (HR Max–HR Min, RMSSD, SDNN, TI, and TINN), one frequency-domain metric (LF power), and three non-linear metrics (D2, SD1, SD2) significantly more than RSMT at 12 cpm. There were no differences between 1 and 6 cpm on these measures. The 1-cpm rate (~ 0.02 Hz) may have stimulated the hypothesized vascular tone baroreflex between 0.02 and 0.055 Hz. RSMT at 1 or 6 cpm provides clients with an alternative exercise for increasing HRV for patients who find slow-paced breathing challenging or medically unsafe.
 
Article
This paper outlines the early history and contributions our laboratory, along with our close advisors and collaborators, has made to the field of heart rate variability and heart rate variability coherence biofeedback. In addition to the many health and wellness benefits of HRV feedback for facilitating skill acquisition of self-regulation techniques for stress reduction and performance enhancement, its applications for increasing social coherence and physiological synchronization among groups is also discussed. Future research directions and applications are also suggested.
 
Article
This article celebrates the contributors who inspired Truman’s heart rate variability (HRV) research program. These seminal influences include Robert Fried, Richard Gevirtz, Paul Lehrer, Erik Peper, and Evgeny Vaschillo. The Truman State University Applied Psychophysiology Laboratory’s HRV research has spanned five arcs: interventions to teach diaphragmatic breathing, adjunctive procedures to increase HRV, HRV biofeedback (HRVB) training studies, the concurrent validity of ultra-short-term HRV measurements, and rhythmical skeletal muscle tension strategies to increase HRV. We have conducted randomized controlled trials, primarily using within-subjects and mixed designs. These studies have produced eight findings that could benefit HRVB training. Effortful diaphragmatic breathing can lower end-tidal CO2 through larger tidal volumes. A 1:2 inhalation-to-exhalation (I/E) ratio does not increase HRV compared to a 1:1 I/E ratio. Chanting “om,” listening to the Norman Cousins relaxation exercise, and singing a fundamental note are promising exercises to increase HRV. Heartfelt emotion activation does not increase HRV, enhance the effects of resonance frequency breathing, “immunize” HRV against a math stressor, or speed HRV recovery following a math stressor. Resonance frequency assessment achieved moderate (r = 0.73) 2-week test-reliability. Four weeks of HRVB training increased HRV and temperature, and decreased skin conductance level compared with temperature biofeedback training. Concurrent-validity assessment of ultra-short-term HRV measurements should utilize rigorous Pearson r and limits of agreement criteria. Finally, rhythmical skeletal muscle tension can increase HRV at rates of 1-, 3-, and 6-cpm. We describe representative studies, their findings, significance, and limitations in each arc. Finally, we summarize some of the most interesting unanswered questions to enable future investigators to build on our work.
 
Article
Physical activity can improve health as well as reduce stress and the risk of developing several widespread diseases. However, there exists no accepted standard biomedical examination-method for stress evaluation. The purpose of this study was to investigate the effect of regular physical activity on stress and wellness as well as the evaluation of potential biomarkers in this field. This study included 105 people (mean age = 36.57 ± 1.4 years) who were randomly assigned into the exercise group 1 (EG-1) (n = 41), the exercise group 2 (EG-2) (n = 30), and the control group (CG) (n = 34). Measurements of stress and wellness were obtained by Multiscan BC-OXI before and after experimental period. This device presents a multifrequency segmental body composition 3D analyser with digital pulse oximeter. The key indicators of stress as well as for wellness were significantly improved in the EG-1. Parasympathetic activity showed significant changes as potential stress biomarker. Statistically significant gender differences were not observed in the comparable groups. The results suggest that the stress resistance and well-being significantly improved in the EG-1 due to regular physical activity. However, further research is necessary to determine effects of physical activity on integral health indicators.
 
Participants flowchart
The HRV reactivity (A–B) for the anger recall task at pre-test and post-test between the HRV-BF and control groups. *p < .05; B = baseline; A = anger recall; A–B = anger recall − baseline
The HRV recovery (AR-A) for the anger recall task at pre-test and post-test between the HRV-BF and control groups. *p < .05; A = agner recall; AR = anger recovery; AR − A = anger recovery − anger recall
Article
Patients with coronary artery disease (CAD) often experience anger events before cardiovascular events. Anger is a psychological risk factor and causes underlying psychophysiological mechanisms to lose balance of the autonomic nervous system (ANS). The heart rate variability (HRV) was the common index for ANS regulation. It has been confirmed that heart rate variability biofeedback (HRV-BF) restored ANS balance in patients with CAD during the resting state. However, the effects of HRV-BF during and after the anger event remain unknown. This study aimed to examine the effects of HRV-BF on ANS reactivity and recovery during the anger recall task in patients with CAD. This study was a randomized control trial with a wait-list control group design, with forty patients in the HRV-BF group (for six sessions) and 44 patients in the control group. All patients received five stages of an anger recall task, including baseline, neutral recall task, neutral recovery, anger recall task, and anger recovery. HRV reactivity in the HRV-BF group at the post-test was lower than that in the control group. HRV recovery at the post-test in the HRV-BF group was higher than that in the control group. The HRV-BF reduced ANS reactivity during anger events and increased ANS recovery after anger events for CAD patients. The possible mechanisms of HRV-BF may increase total HRV, ANS regulation, and baroreflex activation at anger events for patients with CAD, and may be a suitable program for cardiac rehabilitation.
 
Normal blood pressure (BP) response during the Valsalva maneuver (VM). The VM consists of four main phases: phase I (I), early phase II (IIE), late phase II (IIL), phase III and phase IV. The first two phases of the VM are generated while the patient maintains an expiratory pressure between 30–40 mmHg for 15 s. Phases III and IV are generated after completion of the maneuver
Article
Chronic orthostatic intolerance (COI) is defined by changes in heart rate (HR), blood pressure (BP), respiration, symptoms of cerebral hypoperfusion and sympathetic overactivation. Postural tachycardia syndrome (POTS) is the most common form of COI in young adults and is defined by an orthostatic increase in heart rate (HR) of ≥ 30 bpm in the absence of orthostatic hypotension. However, some patients referred for evaluation of COI symptoms do not meet the orthostatic HR response criterion of POTS despite debilitating symptoms. Such patients are ill defined, posing diagnostic and therapeutic challenges. This study explored the relationship among cardiovascular autonomic control, the orthostatic HR response, EtCO2 and the severity of orthostatic symptoms and fatigue in patients referred for evaluation of COI. Patients (N = 108) performed standardized testing protocol of the Autonomic Reflex Screen and completed the Composite Autonomic Symptom Score (COMPASS-31) and the Fatigue Severity Scale (FSS). Greater severity of COI was associated with younger age, larger phase IV amplitude in the Valsalva maneuver and lower adrenal baroreflex sensitivity. Greater fatigue severity was associated with a larger reduction in ETCO2 during 10 min of head-up tilt (HUT) and reduced low-frequency (LF) power of heart rate variability. This study suggests that hemodynamic changes associated with the baroreflex response and changes in EtCO2 show a stronger association with the severity of orthostatic symptoms and fatigue than the overall orthostatic HR response in patients with COI.
 
Topographical maps of pre-to-post EEG change of neurofeedback group. EC Eye closed, EO eye open
Topographical maps of pre-to-post EEG change of CBT-I group. EC Eye closed, EO eye open
Topographical maps of post-to-follow up EEG change of neurofeedback group. EC Eye closed, EO eye open
Topographical maps of post-to-follow up EEG change of CBT-I group. EC eye closed; EO eye open
Article
Insomnia is a common disease that negatively affects patients both mentally and physically. While insomnia disorder is mainly characterized by hyperarousal, a few studies that have directly intervened with cortical arousal. This study was conducted to investigate the effect of a neurofeedback protocol for reducing cortical arousal on insomnia compared to cognitive-behavioral treatment for insomnia (CBT-I). Seventeen adults with insomnia, free of other psychiatric illnesses, were randomly assigned to neurofeedback or CBT-I. All participants completed questionnaires on insomnia [Insomnia Severity Index (ISI)], sleep quality [Pittsburgh Sleep Quality Index (PSQI)], and dysfunctional cognition [Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS-16)]. The neurofeedback group showed decreases in beta waves and increases in theta and alpha waves in various areas of the electroencephalogram (EEG), indicating lowered cortical arousal. The ISI and PSQI scores were significantly decreased, and sleep efficiency and sleep satisfaction were increased compared to the pre-treatment scores in both groups. DBAS scores decreased only in the CBT-I group (NF p = 0.173; CBT-I p = 0.012). This study confirmed that neurofeedback training could alleviate the symptoms of insomnia by reducing cortical hyperarousal in patients, despite the limited effect in reducing cognitive dysfunction compared to CBT-I.
 
Difference between sex in state anxiety pre and post neutral and unpleasant sessions. *Significantly higher than pre time of unpleasant session for the same sex; ¥ Significantly higher than man, for post time of the unpleasant session; # Significantly higher than post time of the neutral session for the same sex. There was no statistical difference among time and sex on the neutral session
Difference between sex in state anger pre and post neutral and unpleasant sessions. *Significantly higher than pre time of unpleasant session for the same sex; ¥ Significantly higher than man, for post time of the unpleasant session; # Significantly higher than post time of the neutral session for the same sex. There was no statistical difference among time and sex on the neutral session
Difference between sexes in mean heart rate between sex among sessions. bpm: beats per minute; *Significantly higher than neutral session for the same sex; #Significantly lower than women (unpleasant session)
Article
To evaluate the heart rate response, emotion and changes in anxiety and anger levels after exposure to unpleasant pictures from the International Assessment Pictures System (IAPS) compared with neutral picture exposure in healthy individuals. Forty participants (23 women) visited the laboratory on two occasions. State anger and state anxiety levels were evaluated pre-and post-visualization of a set of IAPS pictures and heart rate was monitored during exposure. Two different picture sets were utilized-one with neutral pictures (that served as the control) and the other with unpleasant pictures. State anxiety and state anger were higher in post-unpleasant session for women than before (p < 0.001). For men, only state anxiety was higher in the post-unpleasant session (p < 0.001). State anxiety (p = 0.004) and state anger (p < 0.001) post-unpleasant session was higher for women than in men. The pleasure and dominance domains were lower in the unpleasant session for both men and women (p < 0.001), and the arousal domain was higher for both men and women (p < 0.001) than in the neutral session. In the unpleasant session, arousal was higher (p = 0.004), and dominance was lower (p < 0.001) among women than among men, but no difference in pleasure was found (p > 0.05). For women, average heart rate was higher on unpleasant session, compared to neutral (p = 0.01), but not for men (p > 0.05). Women are more sensitive and react strongly to unpleasant picture exposure. The IAPS unpleasant session was not able to induce anger levels in men.
 
Radar diagram for differences in personality profile between people in addiction centers and controls. A agreeableness, E extraversion, N neuroticism, C conscientiousness, O openness to experience
Article
Drug treatment centres provide the highest level of rehab services for patients diagnosed with drug addictions. Most inpatient drug rehab programs focus on medical detox and mental health interventions. However, how to optimize the later remains a challenge. The aim of this study was to examine the psychophysiological and psychosocial profile of patients attending drug addiction centres in comparation with the general population. A total of 105 inpatient drug rehab patients and 50 participants from the general population were compared based on standardized psychophysiological and psychosocial measures. Results of this study suggest that patients attending drug addiction centers differ from general population in several different psychophysiological and psychosocial factors. Patients reported significantly lower levels of physical activity and increased sympathetic responsiveness, and significantly higher levels in loneliness, psychologically inflexibility and neuroticism. The results of this study highlight the importance of address healthy lifestyle behaviors such as sport practice and psychological variables such as loneliness, psychological (in)flexibility and neuroticism to improve current programs aim to prevent or reduce problematic drug consumptions.
 
Power spectra (upper panels) and RR interval trendgrams (lower panels) in a representative participant during relaxation training (Autogenic Training) under frequency-controlled respiration at 0.25 Hz. AT1–AT3 = three consecutive sessions of the relaxation training. Reconstructed from Sakakibara et al. (1994)
Amplitude of the high-frequency (HF) components of pulse rate variability during sleep (left panel) and state anxiety score of the STAI immediately before participants’ habitual bedtime (right panel) at four time points. Time 1–4 = four consecutive nights. Data are presented as mean ± SE. Reconstructed from Sakakibara and Hayano (2015)
Power spectra (upper panels) and RR interval trendgrams (lower panels) in a representative participant during baseline, paced breathing at 15 cpm (0.25 Hz), and that at LF-peak frequency (0.09 Hz). Since the resonance frequency is expected to occur from 4.5 to 6.5 cpm (Lehrer, 2021), the peak frequency of the LF component was determined as being between 0.075 and 0.108 Hz. If multiple peaks appeared in the frequency range, the highest peak was chosen as frequency for paced breathing. Reconstructed from Sakakibara et al. (2020)
Article
This review summarizes my own involvement in heart rate variability (HRV) and HRV biofeedback studies, as a tribute to the late Dr. Evgeny Vaschillo. I first review psychophysiological studies on behavioral stress and relaxation performed in my laboratory using an assessment of cardiac parasympathetic activity. Although magnitude of high-frequency (HF) component of HRV corresponding respiratory sinus arrhythmia (RSA) is widely used as an index of cardiac parasympathetic function, a respiratory confound during stress or relaxation may have interfered with the proper assessment of the HF HRV. An enhanced method under frequency-controlled respiration at 0.25 Hz provided a reliable assessment of cardiac parasympathetic activity. I then review findings from HRV biofeedback research in my laboratory. Based on the hypothesis that RSA measured as an HF component of HRV represents cardiorespiratory resting function, it was demonstrated that HRV biofeedback before sleep enhanced the magnitude of HF HRV during sleep, a cardiorespiratory resting function. Moreover, by focusing on the spectral peak of the low-frequency (LF) component of HRV, paced breathing at the LF-peak frequency was shown to increase baroreflex sensitivity. Finally, I describe the potential of slow-paced abdominal breathing (i.e., Tanden breathing) performed in Zen meditation. The concept of Tanden breathing as described in a regimen from early modern Japan is introduced, and recent research findings on slow-paced abdominal breathing are summarized. Future research directions of slow-paced abdominal breathing are also discussed.
 
Article
This paper reviews the published work of me along with my students and close colleagues on the topic of heart rate variability biofeedback (HRVB). It includes early research by Vaschillo documenting resonance characteristics of the baroreflex system that causes large oscillations in heart rate when breathing at resonance frequency, research on heart rate variability as a marker of parasympathetic stress response in asthma, and HRVB as a treatment for asthma and depression. Many questions about HRVB remain unresolved, and important questions for future research are listed.
 
Article
Lehrer and Woolfolk are major figures who have led the field of stress management for four decades. Here they have assembled a gifted team of expert authors, ranging from Jonathan Smith on relaxation to Alice Meuret and Thomas Ritz on capnometric training to Shirley Telles and colleagues on yoga for stress management. The text Principles and Practice of Stress Management has long provided the most comprehensive scientifically informed resource for understanding stress and stress management. The fourth edition updates the scientific research, introduces new topics, and sharpens the focus in many chapters. Nevertheless, the preface of the fourth edition emphasizes the continued relevance of this book for the lay audience, human beings seeking guidance for managing their life stress.
 
Women with HIV reported significantly fewer A numbers of ruminative thoughts and B symptoms of depression compared to women who did not train with 6 weeks of combined meditation and aerobic exercise. Women who trained also reported significant reductions in C perceived stress, D trauma-related cognitions, and E anxiety symptoms, while responses in women who did not train did not change. *p < 0.05, **p < 0.01, ***p < 0.001
A Decreases in rumination as assessed with the Ruminative Responses Scale persisted for 6 months but not 3 months. B Decreases in depressive symptoms as assessed with the Beck Depression Inventory persisted 3 months and 6 months after training. C Decreases in perceived stress as assessed with the Perceived Stress Scale decreased after training but not 3 months and 6 months after training. *p < 0.05, **p < 0.01, ***p < 0.001
A Behavioral Pattern Separation Task adapted from Stark and colleagues (2013). Participants initially encoded a series of everyday objects. The encoding phase was immediately followed by a surprise recognition test that had 64 identical images to those from the encoding phase (old), 64 novel objects not previously seen, and 64 objects similar to what participants had seen before in the encoding phase but not exactly the same. B Women with HIV who engaged in 6 weeks of training significantly improved on pattern separation accuracy (assessed by the percentage of correct responses to similar items), while performance in women who did not train did not change *p < 0.05. C Women with HIV with recognition memory scores of 80% or above prior to training (n = 8) were assessed on pattern separation scores (calculated as the percentage of correct responses to similar objects minus the percentage of incorrect similar responses to novel objects). Their performance improved after 6 weeks of combined meditation and aerobic exercise training (p < 0.05)
Article
Mental and physical (MAP) training targets the brain and the body through a combination of focused-attention meditation and aerobic exercise. The following feasibility pilot study tested whether 6 weeks of MAP training improves mental health outcomes, while enhancing discrimination learning and heart rate variability (HRV) in a group of women living with human immunodeficiency virus (HIV) and other stress-related conditions. Participants were assigned to training (n = 18) or no-training control (n = 8) groups depending on their ability and willingness to participate, and if their schedule allowed. Training sessions were held once a week for 6 weeks with 30 min of meditation followed by 30 min of aerobic exercise. Before and after 6 weeks of training, participants completed the Behavioral Pattern Separation Task as a measure of discrimination learning, self-report questionnaires of ruminative and trauma-related thoughts, depression, anxiety, and perceived stress, and an assessment of HRV at rest. After training, participants reported fewer ruminative and trauma-related thoughts, fewer depressive and anxiety symptoms, and less perceived stress (p’s < 0.05). The positive impact on ruminative thoughts and depressive symptoms persisted 6 months after training. They also demonstrated enhanced discrimination of similar patterns of information (p < 0.05). HRV did not change after training (p > 0.05). Combining mental and physical training is an effective program for enhancing mental health and aspects of cognition in women living with HIV, although not necessarily through variance in heart rate.
 
PRISMA flowchart of screening, exclusion, and inclusion criteria
Article
Over the past decades, virtual reality (VR) has found its way into biofeedback (BF) therapy programs. Using VR promises to overcome challenges encountered in traditional BF such as low treatment motivation, low attentional focus and the difficulty of transferring learnt abilities to everyday life. Yet, a comprehensive research synthesis is still missing. Hence, this scoping review aims to provide an overview over empirical studies on VR based BF regarding key outcomes, included samples, used soft- and hardware, BF parameters, mode of application and potential limitations. We systematically searched Medline, PsycINFO, Scopus, CINAHL, Google Scholar and Open Grey for empirical research. Eighteen articles met the inclusion criteria. Samples mostly consisted of healthy (44.4%) and/or adult (77.7%) participants. Outcomes were mainly anxiety (44.4%), stress (44.4%) or pain reduction (11.1%), which were reduced by the VR-BF interventions at least as much as by classical BF. Participants in VR-BF interventions showed higher motivation and involvement as well as a better user experience. Heart rate or heart rate variability were the most frequently used BF parameters (50.0%), and most VR-BF interventions (72.2%) employed a natural environment (e.g., island). Currently, there is no clear evidence that VR-BF is more effective than traditional BF. Yet, results indicate that VR-BF may have advantages regarding motivation, user experience, involvement and attentional focus. Further research is needed to assess the specific impact of VR and gamification. Also, testing a broader range of clinical and younger samples would allow more far-reaching conclusions.
 
Article
The natural tendency of the mind to wander (i.e., mind wandering), is often connected to negative thoughts and emotional states. On the other hand, mindfulness (i.e., the ability to focus one’s attention on the present moment in a non-judgmental way) has acquired a growing interest in recent years given its beneficial role in improving awareness and self-regulation. Starting from previous evidence, this study aims to clarify the psychological, physiological, and affective impact of a mindfulness exercise on mind wandering. Twenty-eight non-expert female meditators were recruited for this study. Heart rate variability (HRV), state mindfulness, mind wandering manifestations, and affective states, were recorded during a baseline condition, a mindfulness breathing observation exercise, and a final rest condition. Subjects reported significant decreases in mind wandering comparing baseline and mindfulness. Changes in mind wandering were mirrored by changes in HRV, with higher HRV during the breathing observation exercise. Significant associations were found between scores of mindfulness, mind wandering, and affective states measured during the task. Our findings confirmed the role of mindfulness in reducing mind wandering and increasing HRV. Results are discussed considering mindfulness associations with self-regulation and well-being.
 
This figure represents conceptual moderation models tested in the current investigation. A Represents a moderation test in which measures of HRV are independent variables, gender is the moderating variable, and measures of cardiac chronotropy are dependent variables. B Represents a similar model, however cvHRV variables take the place of unadjusted HRV variables as independent variables. C Represents the reverse model such that cardiac chronotropic measures are the independent variable, gender as a moderator, and both adjusted and unadjusted measures of HRV as dependent variables
Gender differences in the association between SDNN and cardiac chronotropy. A and B Show scatterplots of natural log-transformed (ln) standard deviation of inter-beat-intervals (lnSDNN) and both inter-beat-intervals (IBI in ms) and heart rate (HR in beats per minute; bpm), respectively. Within these plots, slopes are labeled differentially as a function of gender. C and D Depict conditional effects of significant moderation. Higher and lower estimates of SDNN were derived from ± 1SD from the mean (see “Methods” for details)
Gender differences in the association between RMSSD and cardiac chronotropy. 3 and B Show scatterplots of natural log-transformed (ln) root mean square of successive differences (lnRMSSD) and both inter-beat-intervals (IBI in ms) and heart rate (HR in beats per minute; bpm), respectively. Within these plots, slopes are labeled differentially as a function of gender. C and D depict conditional effects of significant moderation. Higher and lower estimates of RMSSD were derived from ± 1SD from the mean (see “Methods” for details)
Gender differences in the association between HF and cardiac chronotropy. A and B Show scatterplots of natural log-transformed (ln) high-frequency (lnHF) and both inter-beat-intervals (IBI in ms) and heart rate (HR in beats per minute; bpm), respectively. Within these plots, slopes are labeled differentially as a function of gender. C and D Depict conditional effects of significant moderation. Importantly, at any given level of HRV, the heart period is quicker in women relative to men (see C for example). For any given level of HR, HRV is higher in women relative to men (see D for example). For example, an IBI of ~ 800 ms (C) and an HR of ~ 77 bpm (D) yields a natural log-transformed HF-HRV value of ~ 6.50 for women and ~ 5.75 for men (see horizontal lines). Higher and lower estimates of HF were derived from ± 1SD from the mean (see “Methods” for details)
Article
There is a continuing debate concerning “adjustments” to heart period variability [i.e., heart rate variability (HRV)] for the heart period [i.e., increases inter-beat-intervals (IBI)]. To date, such arguments have not seriously considered the impact a demographic variable, such as gender, can have on the association between HRV and the heart period. A prior meta-analysis showed women to have greater HRV compared to men despite having shorter IBI and higher heart rate (HR). Thus, it is plausible that men and women differ in the association between HRV and HR/IBI. Thus, the present study investigates the potential moderating effect of gender on the association between HRV and indices of cardiac chronotropy, including both HR and IBI. Data from 633 participants (339 women) were available for analysis. Cardiac measures were assessed during a 5-min baseline-resting period. HRV measures included the standard deviation of inter-beat-intervals, root mean square of successive differences, and autoregressive high frequency power. Moderation analyses showed gender significantly moderated the association between all HRV variables and both HR and IBI (each p < 0.05). However, results were not consistent when using recently recommended HRV variables “adjusted” for IBI. Overall, the current investigation provides data illustrating a differential association between HRV and the heart period based on gender. Substantial neurophysiological evidence support the current findings; women show greater sensitivity to acetylcholine compared to men. If women show greater sensitivity to acetylcholine, and acetylcholine increases HRV and the heart period, then the association between HRV and the heart period indeed should be stronger in women compared to men. Taken together, these data suggest that routine “adjustments” to HRV for the heart period are unjustified and problematic at best. As it relates to the application of future HRV research, it is imperative that researchers continue to consider the potential impact of gender.
 
A magnified (2-min) view of the HRVisualizer post-analysis display strip showing RF at 4.55 bpm approximately 12 min and 50 s into the session
Distribution of stepped method (left) and sliding method (right) RF values
Article
This study validated a more exact automated method of determining cardiovascular resonance frequency (RF) against the “stepped” protocol described by Lehrer et al. (Appl Psychophysiol Biofeedback 25(3):177–191, https://doi.org/10.1023/a:1009554825745, 2000; in Foundations of heart rate variability biofeedback: A book of readings, The Association for Applied Psychophysiology and Biofeedback, pp 9–19, 2016). Thirteen participants completed a 15-min RF determination session by each method. The “stepped” protocol assesses HRV in five 3-min stationary windows from 4.5 to 6.5 breaths per minute (bpm), decreasing in 0.5 bpm steps. Multiple criteria, subjectively weighted by the clinician, determines RF. For this study, the proposed method used a sliding window with a fixed rate of change (67.04 ms per breath) at each of 78 breath cycles ranging from 4.25 to 6.75 bpm. Its algorithm analyzes IBI to locate the midpoint of the 1-min region of stable maximum peak-trough variability. RF is quantified from breath duration at that point. The software generates a visual display of superimposed HR and breathing data. Thus, the new method fully automates RF determination. Eleven of the 13 matched pairs fell within the 0.5 bpm resolution of the stepped method. Comparisons of LF power generated by the autoregressive (AR) spectral method showed a strong correlation in LF power production by the stepped and sliding methods (R = 0.751, p = 0.000). The “sliding” pacing protocol was favored by 69% of participants (p < 0.02). The new, fully-automated, method may facilitate both in-person and remote HRV biofeedback training. Software is available open-source.
 
A-B URGOnight headband and URGOnight mobile app neurofeedback training session screen. A The headband, adjustable to head size, with two measuring dry electrodes over the sensori-motor cortex. B Neurofeedback training screen: the bar on the left fills in real-time when SMR power increases. The threshold is displayed by a level on top of the gage, the animated wallpaper is animated whenever SMR activity exceeds the threshold (here, the jellyfishes will illuminate and disappear as long as the participant manages to keep his or her SMR activity above threshold)
A–D: the effects on PSQI Total (A), PSQI Sleep Duration (B), HSDQ Total (C), and HSDQ Insomnia (D) over the course of treatment. Repeated measures ANOVAs using Sample (40 vs 60 sessions) as a between-subject factor and Time (pre-treatment, 20 sessions, and post-treatment) as a within-subject factor showed a significant effect of Time for PSQI Total (A: F(2,34) = 19.81, p < 0.001; d = 0.78), PSQI Sleep Duration (B: F(1,36) = 18.27, p < 0.001; d = 0.52), HSDQ Total (C: F(2,34) = 21.77, p < 0.001; d = 0.80), and HSDQ Insomnia (D: F(2,34) = 13.19, p < 0.001, d = 0.79). No interactions with Sample (p > 0.285) or main effects of Sample (p > 0.628) were observed
Average learning analysis regression slopes (relative SMR power z-scores within sessions, average over all sessions, error bars =  ± SD) for (A) learner subjects (N=11\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$N=11$$\end{document}) who exhibit a positive slope (B) and non-learner subjects (N=21\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$N=21$$\end{document}) who exhibit a negative one
Article
SMR neurofeedback shows potential as a therapeutic tool for reducing sleep problems. It is hypothesized that SMR neurofeedback trains the reticulo-thalamocortical-cortical circuit involved in sleep-spindle generation. As such, strengthening this circuit is hypothesized to reduce sleep problems. The current study aims to investigate the effectiveness of a home-based device that uses SMR neurofeedback to help reduce sleep problems. Thirty-seven participants reporting sleep problems received the SMR neurofeedback-based program for 40 ( n = 21) or 60 ( n = 16) sessions. The Pittsburgh Sleep Quality Index (PSQI) and Holland Sleep Disorders Questionnaire (HSDQ) were assessed at baseline, session 20, outtake, and follow-up (FU). Actigraphy measurements were taken at baseline, session 20, and outtake. Significant improvements were observed in PSQI Total ( d = 0.78), PSQI Sleep Duration ( d = 0.52), HSDQ Total ( d = 0.80), and HSDQ Insomnia ( d = 0.79). Sleep duration (based on PSQI) increased from 5.3 h at baseline to 5.8 after treatment and 6.0 h. at FU. No effects of number of sessions were found. Participants qualified as successful SMR-learners demonstrated a significantly larger gain in sleep duration ( d = 0.86 pre-post; average gain = 1.0 h.) compared to non-learners. The home-based SMR tele-neurofeedback device shows the potential to effectively reduce sleep problems, with SMR-learners demonstrating significantly better improvement. Although randomized controlled trials (RCTs) are needed to further elucidate the specific effect of this device on sleep problems, this is the first home-based SMR neurofeedback device using dry electrodes demonstrating effectiveness and feasibility.
 
Article
To evaluate the heart rate response, emotion and changes in anxiety and anger levels after exposure to unpleasant pictures from the International Assessment Pictures System (IAPS) compared with neutral picture exposure in healthy individuals. Forty participants (23 women) visited the laboratory on two occasions. State anger and state anxiety levels were evaluated pre- and post-visualization of a set of IAPS pictures and heart rate was monitored during exposure. Two different picture sets were utilized—one with neutral pictures (that served as the control) and the other with unpleasant pictures. State anxiety and state anger were higher in post-unpleasant session for women than before (p < 0.001). For men, only state anxiety was higher in the post-unpleasant session (p < 0.001). State anxiety (p = 0.004) and state anger (p < 0.001) post-unpleasant session was higher for women than in men. The pleasure and dominance domains were lower in the unpleasant session for both men and women (p < 0.001), and the arousal domain was higher for both men and women (p < 0.001) than in the neutral session. In the unpleasant session, arousal was higher (p = 0.004), and dominance was lower (p < 0.001) among women than among men, but no difference in pleasure was found (p > 0.05). For women, average heart rate was higher on unpleasant session, compared to neutral (p = 0.01), but not for men (p > 0.05). Women are more sensitive and react strongly to unpleasant picture exposure. The IAPS unpleasant session was not able to induce anger levels in men.
 
Topographic maps for A absolute and (B) relative power and the theta/beta ratio for the male AD/HD and control groups. Scales: absolute power in µV², relative power in %
EEG frequency distribution for each group, averaged across all sites
Article
This study examined sex differences in the EEG of adults diagnosed with Attention-Deficit/Hyperactivity Disorder (AD/HD) according to DSM-5 criteria. Sixteen females and 16 males with AD/HD, and age- and sex-matched control groups, had an eyes-closed resting EEG recorded from 19 electrode sites. EEGs were Fast Fourier transformed and estimates for total power, absolute and relative power in the delta, theta, alpha, beta and gamma bands, and the theta/beta ratio, were analysed across nine cortical regions. Males with AD/HD, compared with male controls, had globally reduced absolute beta, globally elevated relative theta, and a larger theta/beta ratio. In contrast, no global effects emerged between females with and without AD/HD. Significant group interactions indicated that globally elevated relative theta and elevated frontal-midline theta/beta ratio noted in males with AD/HD differed significantly from results in females. There are statistically significant EEG differences in relative theta and the theta/beta ratio between males and females with and without AD/HD. These results indicate that AD/HD affects the EEG activity of males and females differently. This study helps confirm the need for further independent examination of AD/HD within female populations.
 
Participant disposition
Outcomes on primary and secondary measures
Article
Evidence‐based treatments for posttraumatic stress disorder (PTSD), including psychotherapies and medications, have high dropout and nonresponse rates, suggesting that more acceptable and effective treatments for PTSD are needed. Capnometry Guided Respiratory Intervention (CGRI) is a digital therapeutic effective in panic disorder that measures and displays end-tidal carbon dioxide (EtCO2) and respiratory rate (RR) in real-time within a structured breathing protocol and may have benefit in PTSD by moderating breathing and EtCO2 levels. We conducted a single-arm study of a CGRI system, Freespira®, to treat symptoms of PTSD. Participants with PTSD (n = 55) were treated for four weeks with twice-daily, 17-min at-home CGRI sessions using a sensor and tablet with pre-loaded software. PTSD and associated symptoms were assessed at baseline, end-of treatment, 2-months and 6-months post-treatment. Primary efficacy outcome was 50% of participants having ≥ 6-point decrease in Clinician Administered PTSD Scale (CAPS-5) score at 2-month follow up. Tolerability, usability, safety, adherence and patient satisfaction were assessed. CGRI was well tolerated, with 88% [95% CI 74–96%] having ≥ 6-point decrease in CAPS-5 scores at 2-months post-treatment follow up. Mean CAPS-5 scores decreased from 49.5 [s.d. = 9.2] at baseline to 27.1 [s.d. = 17.8] at 2-months post-treatment follow up. Respiratory rate decreased and EtCO2 levels increased. Associated mental and physical health symptoms also improved. This CGRI intervention was safe, acceptable, and well-tolerated in improving symptoms in this study in PTSD. Further study against an appropriate comparator is warranted. Trial registration Clinicaltrials.gov NCT#03039231.
 
Distribution and linear regression between ∆ HR (change in HR during CPT) and peak pain. The two variables correlate positively along a linear line, with R squared of 0.648
Article
To understand the variable response to pain, researchers have examined the change in cardiovascular measures to a uniform painful stimulation. Pain catastrophizing is the tendency to magnify or exaggerate pain sensations, and it affects the outcome of rehabilitation in a clinical setting. Its effect on cardiovascular changes during a painful stimulus is unclear. Twenty-four healthy human participants completed the study. All participants completed a cold pressor test while subjective pain intensity was measured with a numeric pain scale from 0–10. Continuous cardiac output measurements were obtained with finger-pulse plethysmograph waveform analysis. The measurements included systolic and diastolic blood pressure, heart rate averaged over 30 s intervals. Pain catastrophizing and anxiety were assessed using the pain catastrophizing scale (PCS), and Spielberger’s State-Trait Anxiety Inventories, respectively. Peak pain was correlated to pain catastrophizing (r = 0.628, p < 0.01). There was a strong correlation between change in heart rate (HR) and subjective peak pain (r = 0.805, p < 0.01), total PCS (r = 0.474, p < 0.05), and the helplessness subscale of the PCS (r = 0.457, p < 0.05). Peak pain and catastrophizing explained a significant amount of the variance for the change in HR during the cold pressor test (R2 of 0.649 and 0.224 respectively, p = 0.019). These novel findings demonstrate a psycho-physiological relationship between cardiovascular changes and pain catastrophizing. Further research should include participants with subacute or persistent pain.
 
Mean GAD-2 scores across 6 time points
Facebook recruitment Ad
Instructions for correct placement of the Lief smart patch
Article
We assessed the feasibility of using a consumer friendly, heart rate variability biofeedback (HRVB) wearable device in conjunction with a remote stress management coach to reduce symptoms of anxiety. We utilized a discreet, continuously wearable electrocardiogram device, the Lief Smart Patch, which measures and records heart rate and HRV in real time, and guides HRVB exercises using vibrations and visual cues. During the 8-week study, participants (N = 14) wore the Lief Smart Patch, participated in HRVB with the device, utilized the mobile app, and communicated with a remote stress management coach. We collected self-report survey responses to measure symptoms of anxiety (GAD-2) and depression (PHQ-2) every 2 weeks, as well as HRV data throughout the study. Participants’ mean GAD-2 score began at 4.6 out of 6. By the trial’s completion, the group’s mean GAD-2 score dropped to 1.7 (t(13) = 11.0, p < .001) with only 2 of the 14 subjects remaining over the clinical threshold of high anxiety. Similarly, the group’s mean PHQ-2 score dropped from 2.93 to 1.29 (t(13) = 3.54, p < .01). In addition, participants increased their HRV (RMSSD) by an average of + 11.4 ms after participating in a low dose biofeedback exercise. These findings suggest that engaging in HRVB through a discreet wearable device in conjunction with a remote stress management program may be effective for reducing symptoms of anxiety and depression.
 
Article
This study aimed to investigate the relationship between neural efficiency and the ability of an athlete to produce accurate efforts in different perceived intensity zones during a racing scenario. The α/β ratio was used to quantify the neural efficiency during cycling, as it traduced the degree of participants information processing activity with lower cortical activity possible. Twelve trained competitive male cyclists delimited their perceived intensity zones 2 to 6 on a scale to assess the rating of exercise intensity. Then, they performed a 30 min racing scenario during which they had to produce different perceived intensities. The ability of athletes to produce perceived effort with accuracy and their neural efficiency was quantified during the racing scenario. The increase in the neural efficiency with the increase in the effort intensity could partly explain the improvement in athletes’ ability to produce accurately perceived efforts from intensity zones 3 to 6. Moreover, the neural efficiency during the racing scenario was significantly correlated to the ability to produce perceived effort with accuracy at submaximal intensities.
 
Number of presentations per research field at each annual meeting
Percentage of the total number of presentations per field during each decade
Mean scores and standard deviations for subjective comfort (open circles) and sensation of dyspnea (black circles) under paced breathing conditions. Reproduced from Terai and Umezawa (2016)
Device constitution placed inside a stuffed bear. APS air pressure sensor, SV solenoid valve
Stuffed bear (Rilakkuma Kuttari®, San-X) as a paced breathing device
Article
This article provides an overview of the history of the Japanese Society of Biofeedback Research (JSBR) and presents some of its recent advances. Most of the research papers published in the JSBR journal (Biofeedback Kenkyu) have been written in Japanese, and therefore have had very few opportunities to reach global readers. We would like to present some of important findings previously published there. First, we present the history of the JSBR. Secondly, we will focus on paced breathing, which is instrumental in achieving relaxation in heart rate variability biofeedback (HRV-BF). We will look back on the origin of slow-paced breathing in Japan, that could be attributed to the concept of Tanden breathing (abdominal paced breathing) practiced in Zen meditation. Thirdly, we will introduce some of the current research progresses of JSBR, especially focusing on the development of a non-contact sensing technology and relaxation device. Finally, we will explain about a very recent trial, the “Suu-Haa” Relaxation Technique, which we hope may be useful for helping people cope with the SARS-CoV-2 (COVID-19) crisis.
 
A schema of the schedule of neurofeedback in this study (left) and the adopted neurofeedback system (right). The subjects of group A underwent NF in the first feedback period and RF in the second feedback period, while subjects of group B underwent each feedback in reverse order. In the normal neurofeedback, the subject listened to classical music with the eyes closed and Muse mounted on the head. The superimposed white noise was updated every three seconds so that the noise level inversely correlated to the alpha-power, normalized to that of the calibration session. NF normal feedback, RF random feedback, Cal calibration, α-power averaged alpha power in feedback session for every three second, μcalib averaged alpha power in calibration session, σcalib standard deviation of alpha power in calibration session
Cognitive tests and the corresponding brain functions. Eight cognitive tests derived from 5 tasks were used in this study. Four composite categories were generated based on the function each cognitive test was designed to evaluate. The right lower figure illustrates the rough area of the epicenter of each function. TOVA The Test of Variables of Attention, S-PA Standard verbal Paired Associate Learning Test
Comparison of the normalized alpha-power between normal and random neurofeedback. A schema of comparison in a crossover design (a). Yellow-green and gray colors refer to each subject in normal and random neurofeedback (NF and RF), respectively. Comparison between NF and RF regardless of the groups (b). The daily normalized alpha-power in NF was significantly higher than that in RF (p = 0.0383). The time courses of the daily normalized alpha-power are shown separately for group A and B (c). Group A showed a slight increase in NF (yellow-green) and a decrease in RF periods (gray). The daily normalized alpha-power of the late section was significantly higher in NF than RF period (p = 0.047)
Comparison of changes in cognitive functions between responders and non-responders. Classification based on robust regression analysis revealed 6 responders and 4 non-responders (a). Changes in normalized cognitive test scores were compared between responders and non-responders (b). In each test, the change in the z-score was not significantly different between the two groups. A decrease was not observed in responders, whereas 5 out of 8 tests showed a decrease in non-responders. Changes in mean z-scores of each composite category were compared between responders and non-responders (c). In the four composite categories, only short-term memory showed significant difference
Article
Neurofeedback through visual, auditory, or tactile sensations improves cognitive functions and alters the activities of daily living. However, some people, such as children and the elderly, have difficulty concentrating on neurofeedback for a long time. Constant stressless neurofeedback for a long time may be achieved with auditory neurofeedback using music. The primary purpose of this study was to clarify whether music-based auditory neurofeedback increases the power of the alpha wave in healthy subjects. During neurofeedback, white noise was superimposed on classical music, with the noise level inversely correlating with normalized alpha wave power. This was a single-blind, randomized control crossover trial in which 10 healthy subjects underwent, in an assigned order, normal and random feedback (NF and RF), either of which was at least 4 weeks long. Cognitive functions were evaluated before, between, and after each neurofeedback period. The secondary purpose was to assess neurofeedback-induced changes in cognitive functions. A crossover analysis showed that normalized alpha-power was significantly higher in NF than in RF; therefore, music-based auditory neurofeedback facilitated alpha wave induction. A composite category-based analysis of cognitive functions revealed greater improvements in short-term memory in subjects whose alpha-power increased in response to NF. The present study employed a long period of auditory alpha neurofeedback and achieved successful alpha wave induction and subsequent improvements in cognitive functions. Although this was a pilot study that validated a music-based alpha neurofeedback system for healthy subjects, the results obtained are encouraging for those with difficulty in concentrating on conventional alpha neurofeedback. Trial registration: 2018077NI, date of registration: 2018/11/27
 
Electrode positions for the 19-channel EEG apparatus
Article
To compare the pattern of brain waves in video game addicts and normal individuals, a case–control study was carried out on both. Thirty participants were recruited from 14 to 20 years old males from two gaming centers. Twenty healthy participants were gathered from different schools in Tehran using the available sampling method. The QEEG data collection was performed in three states: closed-eye and open-eye states, and during a working memory task. As expected, the power ratios did not show a significant difference between the two groups. Regarding our interest in the complexity of signals, we used the Higuchi algorithm as the feature extractor to provide the input materials for the multilayer perceptron classifier. The results showed that the model had at least a 95% precision rate in classifying the addicts and healthy controls in all three types of tasks. Moreover, significant differences in the Higuchi Fractal Dimension of a few EEG channels have been observed. This study confirms the importance of brain wave complexity in QEEG data analysis and assesses the correlation between EEG-complexity and gaming disorder. Moreover, feature extraction by Higuchi algorithm can render support vector machine classification of the brain waves of addicts and healthy controls more accurate.
 
Article
Functional somatic syndrome (FSS) includes a spectrum of somatic symptoms with insufficient medical explanation. Its underlying pathophysiology is considered to include dysfunctional stress-responsive systems or autonomic dysfunction. Among the autonomic dysfunction readouts, decreased heart rate variability (HRV) has been shown to be characteristic in patients with FSSs. However, its association with quality of life (QOL) has not been clearly examined. We examined the association between short-term resting HRV and QOL in patients with FSS (n = 47) and healthy controls (n = 28). The time domain parameters of HRV were mean heart rate per minute (HR), coefficient of variation of R–R intervals (CvRR) and root mean square of successive differences (RMSSD). The frequency domain parameters of HRV were low-frequency (LF) power and high-frequency (HF) power by power spectrum analysis. The Japanese version of the WHO’s QOL scale (WHOQOL-BREF) (WHO/QOL26) was used for the QOL assessment. There was a significant positive association between the RMSSD and HF power of HRV and all the QOL domains in patients with FSSs who had lower QOL scores on average than controls, while there was no association between HRV and any of the QOL domains in the control group. HF power was more dominantly associated with QOL than the other variables in patients with FSS based on the analysis with a multiple linear regression model. The present study elucidated that the HF power of HRV was dominantly associated with QOL in patients with FSSs who had lower QOL than controls. Vagal index of HRV could be a valuable indicator of the pathological condition and a significant predictor of health-related QOL in patients with FSSs.
 
Example of mother-adolescent (female) dyadic positive (left) and negative (right) interaction. The upper figures represent the IBI series (y axis) from one female adolescent across the 10 min interaction task (x axis). The lower figures represent the respective logarithmic plot of mean (x axis) and standard deviation (y axis) for twenty levels of aggregation (1, 2, 3, 4... 20) of the interbeat intervals time series in the positive (h = 0.7301) and the negative (h = .9108) content interaction tasks
Article
The present study aimed to provide further evidence on the usefulness of non-linear cardiac measures when examining the output of the cardiac system. Scale-invariant self-similarity and entropy, in addition to heart rate variability (HRV) given by time- and frequency-domain measures were calculated in a sample of N = 55 healthy adolescents (Mage = 14.122, SDage = 0.698) during 10-min positive (non-stressful) and negative (stressful) interactions with their mothers. We also explored sex influence in adolescents’ cardiac output using both HRV measures and non-linear cardiac measures. Repeated measures MANOVA revealed a marginal within-group effect for HRV measures, F(3,51) = 2.438, p = 0.075, η²p = 0.125), and a significant within-group effect for non-linear cardiac measures, F(6, 48) = 3.296, p = 0.009, η²p = 0.292, showing a significant decrement in adolescents’ cardiac complexity during the negative interaction. No significant effect for sex was found in either non-linear cardiac measures or HRV measures, but results suggest lower cardiac scaling in females than in males. These findings suggest a real-time scale predominance in heart rate output when adolescents face an aversive situation and support the importance of non-linear cardiac measures to gain insight into the cardiac system and its regulatory mechanisms. Further research is needed to examine sex-differences in cardiac complexity during aversive situations.
 
a Schematic of the experimental procedure. b Illustration of food stimulus, presented as food pictures displayed on a 16' screen over a white background. HRV heart rate variability
Article
Appetitive control is driven by the hedonic response to food and affected by several factors. Heart rate variability (HRV) signals have been used to index autonomic activity and arousal levels towards visual stimuli. The current research aimed to examine the influence of body mass index (BMI), disordered eating behaviors, and sex on the HRV reactivity to food in a nonclinical sample. Thirty-eight healthy male and sixty-one healthy female participants completed questionnaires assessing disordered eating symptoms. HRV was recorded when the participants received visual stimuli of high-calorie food, neutral and negative emotional signals. Generalized estimating equation models were used to investigate the associations between HRV, BMI, disordered eating behaviors, and sex across the three stimulus types. Male participants demonstrated a higher ratio of low-frequency power to high-frequency power (LF/HF) than females across all the stimulus types. An increase in LF/HF reactivity to food signals was observed in all the study subjects. The moderation effect of BMI on LF/HF in response to food signals was also observed. Our study suggests that body weight may play a role in the interaction between sympathetic activity and food stimuli; however, how the interaction between sympathetic activity and food stimuli contributes to diet control warrants further investigation.
 
Mean and confidence interval for each of the three groups, for each period, and for each dependent variable. From left to right: Perceived Stress, log Negative Mood and log RMSSD
Mean and confidence interval of log RMSSD for each period, program, and HRV group. Left: results for the low HRV group; Right: results for the high HRV group
Correlation between the two psychological measures. The higher the Perceived Stress, the greater the Negative Mood
Correlation between variation in the two psychological measures. The more Perceived Stress increased, the more Negative Mood increased
Article
Military personnel are particularly exposed to stressful events, and overexposure to stress is both physically and mentally unhealthy. While stress management programs, such as the Tactics of Optimized Potential (TOP) and Heart Coherence (HC) have been implemented, their efficiency remains to be evaluated. The objective of this randomized control trial was to evaluate the effectiveness of the two programs among a young male population of 180 military fire fighter recruits. Based on two psychological, and one physiological measurement, namely heart rate variability (HRV), we found that both TOP and HC programs significantly increased HRV. This is promising as we know that higher HRV is consistent with better health, in most cases. Moreover, the TOP program significantly reduced perceived stress and negative mood, unlike the HC program. Combining these results, we conclude that while both TOP and HC programs influence physiological measurements, only the TOP modifies psychological evaluations. Finally, we distinguished the effects of the programs on two samples characterized by their HRV level. For the low HRV group, both programs tended to increase their HRV level, while for the high HRV group neither program had a significant effect.
 
Article
There has been an increasing interest in using cardiac indicators of self-regulation in developmental science. Many researchers are interested in unobtrusive mobile devises that are able to collect reliable cardiac data outside of the laboratory setting. Although numerous new ambulatory devices have become available over the last decade, testing these devices on children in comparison to industry gold-standard devices is rarely conducted. The current study evaluated the reliability of one of these ambulatory systems, the BodyGuard2 (FirstBeat), relative to gold-standard laboratory electrocardiogram (Biopac MP150), during active and resting conditions in 4- to 6-year-old children. The BodyGuard2 performed and produced highly similar indices of heart rate variability across resting and active conditions.
 
Article
The Complex Trial Protocol (CTP) is a P300-based Concealed Information Test (CIT). The theoretical underpinnings of the CIT in the context of law enforcement usage are sound. The CTP is said to effectively discriminate individuals who recognize novel and meaningful stimuli and to be countermeasure resistant. Forty-five undergraduate students were assigned to three groups and instructed to perform a computer task using autobiographical data in connection to a mock burglary script. P300 peak-to-peak amplitude differences between probe (surname) and irrelevant (patronymic foils) items accurately identified 100% (14/14) of Innocent Controls (IC), 94% (15/16) of Simply Guilty (SG) participants, and 93% (14/15) of Guilty Countermeasure (GCM) subjects who were asked to counter all stimuli by mentally counting backwards continuously during their test presentation. Increased number of mistakes during the test, from combined cognitive erroneous responses to pop quizzes and behavioral errors with button presses, significantly discriminated GCM from IC and SG individuals. GCM participants committed more errors than IC and SG which did not differ from one another. Reaction Time (RT) was only significant between GCM and IC groups. Implications for forensic issues are discussed.
 
Article
Erectile dysfunction (ED) in younger men is an increasing concern. In middle aged and older men, ED was related to lower resting heart rate variability (HRV), but research in younger men is lacking. The present study examined, in a nonclinical sample of 105 men between 18 and 39 years, the association of ED with several parameters of resting HRV. Scores of the 5-item version of the International Index of Erectile Function (IIEF-5) below 22 were considered as indicating ED. Eighteen men (17.1%) reported ED (mild in 16, mild to moderate in 2). Welch's tests revealed that ED was associated with lower low-frequency power (LF), lower high-frequency power (HF), lower standard deviation of interbeat intervals, and lower standard deviation of the heart rate, which is influenced by both sympathetic and parasympathetic activity. After removing outliers, ED was unrelated to HF. In younger men, erections might be facilitated by a combination of higher parasympathetic tone and relatively higher sympathetic tone in the heart, as indicated by LF and greater standard deviation of the heart rate, a largely overlooked parameter in HRV research.
 
Article
The aim of this study was the comparison of neurofeedback and biofeedback as a combination, against biofeedback intervention alone on athletic performance. 45 novice basketball players were allocated into three groups and assigned accordingly, two experimental and one control group. The experimental group 1 received 24 biofeedback sessions only, experimental group 2 received 24 biofeedback and neurofeedback sessions combined, whereas the control group didn’t receive any form of intervention. Athletic performance scales were used before and after each intervention and multivariate analysis of covariance was used to compare the two groups. Results showed that in comparison to the control group, the athletic performance scales scores in both experimental groups were significantly increased. Furthermore, in experimental group 2 (combined method), we noticed a significantly greater improvement in performance levels than experimental group 1. We concluded that neurofeedback and biofeedback interventions combined, can be used as an effective method to enhance athletic performance.
 
Within session change in EEG power in alpha frequency bands for all five patients (P1; grey dotted line, P2; black dotted line, P3; thick solid grey line, P4; thin solid black line, P5; thick solid black line). Pre EEG represents baseline EEG recorded a few minutes before starting NF training. S1-S6 represents sub-sessions
Comparison of “Pre-NF” EEG alpha power with “during NF” and “deprived NF” (i.e. practicing NF) state for four patients (P2-P5). White bar indicates “Pre-NF” state, black bar indicates “During NF” sate and grey bar indicates “Deprived NF (i.e. Practicing NF)”. Error bar indicates ± SD (standard deviation). The significant change during NF is represented with black asterisk (*p < 0.05). Moreover, the significant change during NF is represented with grey asterisk (*p < 0.05)
Comparison of alpha power obtained from the C4 site of five patients (P1-P5) when performing “mental tasks (reading and arithmetic)” and “during NF” training. White bar indicates “Pre-NF” state, black bar indicates “During NF” sate, dark grey bar indicates “Reading task” and light grey indicates “Mental Arithmetic task”. Error bar indicates ± SD (standard deviation). The significant change during NF is represented with black asterisk (*p < 0.05). Whereas, the significant change during mental task of reading and mathematics is represented with dark grey and light grey asterisks (*p < 0.05)
a Imaginary Coherence scalp maps (16 channels) in Pre-NF (First row) and during NF (second row) in alpha frequency band for five patients (P1; column 1, P2; column 2, P3; column 3, P4; column 4, P5; column 5). Imaginary coherence is presented for training site (i.e. C4 location shown with filled black circles) with the other fifteen electrodes. b Power scalp maps in the alpha frequency band for all five patients before and during neurofeedback (NF). Both figures (a) and (b) are produced for EO condition
a Comparison of alpha EEG power in Pre-NF and during NF state with monopolar montage for five patients (P1–P5). White bar indicates “Pre-NF” state, black bar indicates “During NF with Monopolar Montage” sate. Error bar indicates ± SD (standard deviation). The significant change is represented with asterisk (*p < 0.05). b Comparison of alpha EEG power in Pre-NF and during NF state with Laplacian montage for five patients (P1–P5). White bar indicates “Pre-NF” state, black bar indicates “During NF with Laplacian Montage” sate. Error bar indicates ± SD (standard deviation). The significant change is represented with asterisk (*p < 0.05)
Article
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.
 
Top-cited authors
Richard Gevirtz
  • Alliant International University
Tato M Sokhadze
  • University of South Carolina School of Medicine - Greenville
Manuel F Casanova
  • University of South Carolina School of Medicine - Greenville
Lonnie L. Sears
  • University of Louisville
Martijn Arns
  • Brainclinics Foundation