EEG power spectrum changes due to listening to pleasant music and their relation to relaxation effects

Pentatonic sequences and monaural beats to facilitate relaxation: an EEG study

Introduction

In two studies we investigated if specific acoustic stimulations could be more effective to induce a relaxation response in comparison to silence. Acoustic stimulations included monaural beats and musical sequences based on a pentatonic scale.

Methods

In the first study, 47 participants evaluated monaural beats and pentatonic sequences presented through loudspeakers and varying along three frequencies (0.2, 2, 4 Hz). In the second study, 31 participants relaxed with their eyes closed for 10 min during a passive listening of monaural beats and a pentatonic sequence presented through loudspeakers. A silence condition was introduced as control. All auditory stimuli were designed with a temporal modulation of 0.2 Hz. Concomitant EEG was recorded with a 64-channel system and spectral analysis was performed on delta, theta, alpha, beta, and gamma oscillations to test if each of the three auditory stimulations had a significant effect on EEG spectral power in comparison to silence.

Results

In the first study, pentatonic sequences were evaluated as more pleasant and more relaxing than monaural beats. Pleasantness and relaxation were inversely related to frequency. Visual imagery and emotion induction had higher frequency and were rated with a more positive valence in pentatonic sequences than in monaural beats. In the second study monaural beats in comparison to silence strongly decreased beta and gamma oscillations in the first three minutes and strongly increased theta oscillations in the last three minutes. Pentatonic sequences increased delta, theta, and alpha oscillations in the last three minutes while decreasing beta, and gamma oscillations for the whole auditory stimulation.

Discussion

The results show that auditory signals with a very low temporal modulation (0.2 Hz) could be more effective than silence in inducing a relaxation response. Although 0.2 Hz monaural beats were effective in inducing a relaxation response, they tended to be perceived as unpleasant. Pentatonic sequences could be considered as a better alternative to promote relaxation by auditory stimulation.

Development and validation of the perceived restorative soundscape scale for children

Introduction

Prolonged exposure to noise environments can induce stress and fatigue, even impacting individuals' physical and mental health. Conversely, positive soundscapes can have a beneficial impact on health by alleviating stress and fatigue, promoting psychological recovery. To assess the restorative potential of soundscapes, various scales have been developed to create environments conducive to recovery. However, current research on perceptual restorativeness soundscape scales primarily focuses on adults, lacking a dedicated scale for children to evaluate the restorative potential of their surrounding acoustic environments from their perspective.

Methods

Therefore, this study introduces the development and validation process of the Perceived Restorativeness of Soundscapes Scale for Children (PRSS-C) using survey questionnaires and data statistical analysis.

Results

The study comprises two experiments. Experiment one aims to develop an effective PRSS-C, evaluating the restorative potential of soundscapes in different environments (urban center, urban suburb, and urban peripheral forest) among 185 children aged 10-12. Through a series of analyses, a dual-factor structure scale consisting of 15 items is developed, revealing that the restorative potential of soundscapes is lower in urban centers than in urban suburbs and lower in urban suburbs than in urban peripheral forests. Experiment two aims to further validate the effectiveness of PRSS-C. 244 children aged 10-12 assess the restorative potential of soundscapes in similar environments (two city parks) using the PRSS-C developed in experiment one. Factor analysis confirms the dual-factor structure, with assessment results indicating that the restorative potential of soundscapes in Temple of Heaven Park is lower than in the National Botanical Garden. This suggests that PRSS-C enables children to differentiate the restorative potential of soundscapes in similar environments within the same city, further confirming its effectiveness.

Discussion

This study successfully develops and validates the PRSS-C through two experiments. The use of this scale allows for the assessment of the restorative potential of acoustic environments surrounding children, providing an effective tool for evaluating and creating positive soundscapes for children.

Capacity of Autonomous Sensory Meridian Response on the Reduction of Mental Stress

In a social environment, various types of stress can be overwhelming. Humans frequently encounter these stressful situations in social life. Stress is divided into physical stress and mental stress; the latter is induced by heavy mental workloads and has become a huge social problem, leading to mental disorders and possibly suicide in the worst scenario. Investigations into monitoring mental stress and reducing stressful conditions are, therefore, important for its prevention. In the present study, we focused on autonomous sensory meridian response (ASMR) sound, which is known to improve the human mental condition through its comforting and relaxing effects. We investigated the effect of ASMR on the mental workload induced by mental tasks by the evaluation of EEG activation patterns in normal subjects. Our results showed a significant decrease in alpha-band activity and a significant increase in gamma (high beta)-band activity under the induction of mental workload by mental tasks compared to the resting condition. When applying ASMR sound, alpha- and gamma-band activity under the induction of mental workload by mental tasks was restored to the level of the resting condition. In conclusion, these results indicate that ASMR sound reduces the mental stress induced by mental workload.

Neurophysiological effects of various music genres on electroencephalographic (EEG) cerebral cortex activity

Background

Music has been associated with therapeutic properties for thousands of years across a vast number of diverse regions and cultures. This study expands upon our current understanding of music’s influence on human neurophysiology by investigating the effects of various music genres on cerebral cortex activity using electroencephalography (EEG).

Methods

A randomized, controlled study design was used. EEG data were recorded from 23 healthy adults, ages 19–28, while listening to a music sequence consisting of five randomized songs and two controls. The five studied music genres include: Classical, Tribal Downtempo, Psychedelic Trance (Psytrance), Goa Trance, and Subject Choice.

Results

Controls were associated with lower percentages of beta frequencies and higher percentages of alpha frequencies than the music genres. Psytrance was associated with higher percentages of theta and delta frequencies than the other music genres and controls. The lowest percentages of beta frequencies and highest percentages of alpha frequencies occurred in the occipital and parietal regions. The highest percentages of theta and delta frequencies occurred in the frontal and temporal regions. Subjects with prior music training exhibited increased percentages of delta frequencies in the frontal region. Subject gender and music preference did not have a significant influence on frequency band percentages.

Conclusions

Findings from this study support those of previous music therapy studies and provide novel insights regarding music’s influence on human neurophysiology. These findings also support the hypothesis that music may promote changes in cerebral cortex activity that have similarities to non-rapid eye movement (NREM) sleep, while the listener remains awake.

Acupuncture Relaxation, Vigilance Stage, and Autonomic Nervous System Function: A Comparative Study of Their Interrelationships

Objective: During acupuncture stimulation, autonomic nervous system (ANS) function changes toward being parasympathetic-dominant, with a transient decrease in heart rate (HR). The aim of this research was to determine the relationships between cortical relaxation and vigilance as observed on background electroencephalograms (EEGs), HR, and ANS function during deep acupuncture. Materials and Methods: This comparative study was conducted at Teikyo Heisei University, in Toshima-ku, Tokyo, Japan, with 27 healthy male volunteers. After resting for 20 minutes, the men received manual acupuncture at LI 10 on the left forearm for 2 minutes at a depth of 15-20 mm at a 1-Hz frequency while undergoing concurrent EEG and electrocardiography (ECG) monitoring. Each subject described his level of comfort during acupuncture. HR; power ratios (normalized units [n.u.]) of EEG alpha, beta, delta, and theta waves; and HR variability (HRV) indices were calculated. Results: In the subgroup who experienced discomfort, delta and theta n.u. were decreased while alpha n.u. were increased, indicating increased vigilance and decreased relaxation. In the subgroup who experienced comfort, there were no significant changes. HRV indices suggested parasympathetic-dominant changes in both subgroups. Weak correlations were observed between a decrease of theta n.u. and sympathetic-dominant changes in HRV indices. Conclusions: Alterations in background EEG activities were not the primary factors changing ANS function to parasympathetic-dominant and decreasing HR, but these alterations related to a weak secondary factor changing ANS function. EEG activity by which cortical relaxation and vigilance were represented was the weak secondary factor changing ANS function during acupuncture; the primary factor might be supraspinal reflection.

Automated identification of neural correlates of continuous variables

BACKGROUND

The electroencephalogram (EEG) may be described by a large number of different feature types and automated feature selection methods are needed in order to reliably identify features which correlate with continuous independent variables.

NEW METHOD

A method is presented for the automated identification of features that differentiate two or more groups in neurological datasets based upon a spectral decomposition of the feature set. Furthermore, the method is able to identify features that relate to continuous independent variables.

RESULTS

The proposed method is first evaluated on synthetic EEG datasets and observed to reliably identify the correct features. The method is then applied to EEG recorded during a music listening task and is observed to automatically identify neural correlates of music tempo changes similar to neural correlates identified in a previous study. Finally, the method is applied to identify neural correlates of music-induced affective states. The identified neural correlates reside primarily over the frontal cortex and are consistent with widely reported neural correlates of emotions.

COMPARISON WITH EXISTING METHODS

The proposed method is compared to the state-of-the-art methods of canonical correlation analysis and common spatial patterns, in order to identify features differentiating synthetic event-related potentials of different amplitudes and is observed to exhibit greater performance as the number of unique groups in the dataset increases.

CONCLUSIONS

The proposed method is able to identify neural correlates of continuous variables in EEG datasets and is shown to outperform canonical correlation analysis and common spatial patterns.

Recognizing the degree of human attention using EEG signals from mobile sensors

During the learning process, whether students remain attentive throughout instruction generally influences their learning efficacy. If teachers can instantly identify whether students are attentive they can be suitably reminded to remain focused, thereby improving their learning effects. Traditional teaching methods generally require that teachers observe students' expressions to determine whether they are attentively learning. However, this method is often inaccurate and increases the burden on teachers. With the development of electroencephalography (EEG) detection tools, mobile brainwave sensors have become mature and affordable equipment. Therefore, in this study, whether students are attentive or inattentive during instruction is determined by observing their EEG signals. Because distinguishing between attentiveness and inattentiveness is challenging, two scenarios were developed for this study to measure the subjects' EEG signals when attentive and inattentive. After collecting EEG data using mobile sensors, various common features were extracted from the raw data. A support vector machine (SVM) classifier was used to calculate and analyze these features to identify the combination of features that best indicates whether students are attentive. Based on the experiment results, the method proposed in this study provides a classification accuracy of up to 76.82%. The study results can be used as a reference for learning system designs in the future.

Individual brain-frequency responses to self-selected music

Music is a stimulus which may give rise to a wide range of emotional and cognitive responses. Therefore, brain reactivity to music has become a focus of interest in cognitive neuroscience. It is possible that individual preference moderates the effectof music on the brain. In the present study we examined whether there are common effects of listening to music even if each subject in a sample chooses their own piece of music. We invited 18 subjects to bring along their favorite relaxing music, and their favourite stimulating music. Additionally, a condition with tactile stimulation on the foot and a baseline condition (rest) without stimulation were used. The tactile stimulation was chosen to provide a simple, non-auditory condition which would be identical for all subjects. The electroencephalogram was recorded for each of the 3 conditions and during rest. We found responses in the alpha range mainly on parietal and occipital sites that were significant compared to baseline in 13 subjects during relaxing music, 15 subjects during activating music, and 16 subjects during tactile stimulation. Most subjects showed an alpha desynchronization in a lower alpha range followed by a synchronization in an upper frequency range. However, some subjects showed an increase in this area, whereas others showed a decrease only. In addition, many subjects showed reactivity in the beta range. Beta activity was especially increased while listening to activating music and during tactile stimulation in most subjects. We found interindividual differences in the response patterns even though the stimuli provoked comparable subjective emotions (relaxation, activation), and even if the stimulus was the same for all subjects (somatosensory stimulation). We suggest that brain responsivity to music should be examined individually by considering individual characteristics.

Anxiety and oscillatory responses to emotional facial expressions

In the last decade, event-related potential and functional magnetic resonance imaging studies were very useful in temporal and spatial localization of brain processes involved in the recognition of emotional facial expressions. However, frequency characteristics of the underlying processes have been less studied. Besides, most of the studies did not take into account personality-related individual differences. In this study, effects of explicit and implicit anxiety on the oscillatory dynamics of cortical responses elicited by presentation of angry, neutral, and happy faces were investigated using time-frequency decomposition by means of wavelet transform. Both explicit and implicit anxiety were associated with higher alpha band desynchronization, which was most pronounced during presentation of angry faces. Within theta and delta bands, effects appeared to be opposite for explicit and implicit anxiety measures. In implicitly anxious subjects, frontal delta and theta synchronization upon the presentation of angry and happy (but not neutral) faces was found to be higher than in low anxiety ones, whereas explicit anxiety was associated with a lower theta band synchronization. The results are discussed in terms of conscious and controlled vs. unconscious and intuitive information processing associated with explicit and implicit personality measures.

Motivation, emotion, and their inhibitory control mirrored in brain oscillations

Recent studies suggest brain oscillations as a mechanism for cerebral integration. Such integration can exist across a number of functional domains, with different frequency rhythms associated with each domain. Here, evidence is summarized which shows that delta oscillations depend on activity of motivational systems and participate in salience detection. Theta oscillations are involved in memory and emotional regulation. Alpha oscillations participate in inhibitory processes which contribute to a variety of cognitive operations such as attention and memory. The importance of inhibitory functions associated with alpha oscillations increases during the course of evolution. In ontogenesis, these functions develop later and may be more sensitive to a variety of detrimental environmental influences. In a number of developmental stages and pathological conditions, a deficient alpha and/or increased slow-wave activity are associated with cognitive deficits and a lack of inhibitory control. It is shown that slow-wave and alpha oscillations are reciprocally related to each other. This reciprocal relationship may reflect an inhibitory control over motivational and emotional drives which is implemented by the prefrontal cortex.

Effect of the 5-HT(1A) partial agonist buspirone on regional brain electrical activity in man: a functional neuroimaging study using low-resolution electromagnetic tomography (LORETA)

In a double-blind, placebo-controlled study, the effects of 20 mg buspirone - a 5-HT(1A) partial agonist - on regional electrical generators within the human brain were investigated utilizing three-dimensional EEG tomography. Nineteen-channel vigilance-controlled EEG recordings were carried out in 20 healthy subjects before and 1, 2, 4, 6 and 8 h after drug intake. Low-resolution electromagnetic tomography (LORETA; Key Institute for Brain-Mind Research, software: http://www.keyinst.unizh.ch) was computed from spectrally analyzed EEG data, and differences between drug- and placebo-induced changes were displayed as statistical parametric maps. Data were registered to the Talairach-Tournoux human brain atlas available as a digitized MRI (McConnell Brain Imaging Centre: http://www.bic.mni.mcgill.ca). At the pharmacodynamic peak (1st hour), buspirone increased theta and decreased fast alpha and beta sources. Areas of theta increase were mainly the left temporo-occipito-parietal and left prefrontal cortices, which is consistent with PET studies on buspirone-induced decreases in regional cerebral blood flow and fenfluramine-induced serotonin activation demonstrated by changes in regional cerebral glucose metabolism. In later hours (8th hour) with lower buspirone plasma levels, delta, theta, slow alpha and fast beta decreased, predominantly in the prefrontal and anterior limbic lobe. Whereas the results of the 1st hour speak for a slight CNS sedation (more in the sense of relaxation), those obtained in the 8th hour indicate activation. Thus, LORETA may provide useful and direct information on drug-induced changes in central nervous system function in man.

Responses of the nervous system to low frequency stimulation and EEG rhythms: clinical implications

The present paper reviews literature data on the role of the non-specific central nervous system response mechanisms on the therapeutic effects of relatively weak external stimulations used in clinical practice. The factors affecting the stimulation efficiency and increased sensitiveness of living things to extra-low-frequency periodic stimulations (in the range of from less than 1 Hz to tens of Hz) are discussed. Among the factors determining such effects, the non-specific response mechanisms of the nervous system, the resonance phenomena in different organism systems, and the interaction of external stimulation with endogenous rhythmic processes are analyzed. Most attention is given to endogenous rhythms of the electrical brain activity reflected in the EEG rhythms. A high resolution EEG processing approach that is used to reveal the intrinsic oscillators in the individual EEG spectrum is described. Synchronization of sensory stimulation parameters with the frequencies of intrinsic EEG oscillators is supposed to be an appropriate way to enhance the therapeutic effects of various sensory stimulation treatments. Specific methods for utilizing resonance therapy via sensory stimulation with intrinsic EEG frequencies, and for automatic modulation of stimulation parameters by endogenous organism rhythms are delineated; some preliminary results are described.

EEG coherence or EEG correlation?

In view of the widespread use of electroencephalographic correlation (r) and coherence (Coh) analyses in studying brain functional relationships, it seems important to illustrate results yielded by both methods. Although they are considered as equivalent, they show important differences. Results obtained from r and Coh were compared using: (a) 2 Hz sinusoidal signals, where phase and amplitude were artificially manipulated and, (b) Coh and r spectra obtained between each pair of derivations (C3, C4, F3, F4, T3 and T4) from wakefulness, stage 2, stage 4 and paradoxical sleep (n = 8). The following results were obtained: significant Pearson product-moment coefficients were obtained between r and Coh spectra in the range of 0.86 to 0.96 for interhemispheric and 0.60 to 0.90, for intrahemispheric paris; as a result of principal component analyses, the same three frequency bands were formed for r and Coh spectra with the exception of one single bin; similar results for r and Coh were obtained by two-way ANOVAs (physiological stages by derivations). In conclusion, as expected, a high degree of comparability between r and Coh was observed under normal physiological conditions and with the use of good quality recordings.