EEG Mu Rhythm Research Articles

Effects of home-based EEG neurofeedback training as a non-pharmacological intervention for Parkinson's disease

ObjectivesAberrant movement-related cortical activity has been linked to impaired motor function in Parkinson's disease (PD). Dopaminergic drug treatment can restore these, but dosages and long-term treatment are limited by adverse side-effects. Effective non-pharmacological treatments could help reduce reliance on drugs. This experiment reports the first study of home-based electroencephalographic (EEG) neurofeedback training as a non-pharmacological candidate treatment for PD. Our primary aim was to test the feasibility of our EEG neurofeedback intervention in a home setting. MethodsSixteen people with PD received six home visits comprising symptomology self-reports, a standardised motor assessment, and a precision handgrip force production task while EEG was recorded (visits 1, 2 and 6); and 3 × 1-hr EEG neurofeedback training sessions to supress the EEG mu rhythm before initiating handgrip movements (visits 3 to 5). ResultsParticipants successfully learned to self-regulate mu activity, and this appeared to expedite the initiation of precision movements (i.e., time to reach target handgrip force off-medication pre-intervention = 628 ms, off-medication post-intervention = 564 ms). There was no evidence of wider symptomology reduction (e.g., Movement Disorder Society Unified Parkinson's Disease Rating Scale Part III Motor Examination, off-medication pre-intervention = 29.00, off-medication post intervention = 30.07). Interviews indicated that the intervention was well-received. ConclusionBased on the significant effect of neurofeedback on movement-related cortical activity, positive qualitative reports from participants, and a suggestive benefit to movement initiation, we conclude that home-based neurofeedback for people with PD is a feasible and promising non-pharmacological treatment that warrants further research.

REACTIVITY OF THE EEG SENSORIMOTOR RHYTHMS IN CHILDREN 4–7 YEARS OLD IN SITUATIONS OF HELPING BEHAVIOR

We studied the reactivity features of the EEG mu rhythm amplitude in the individually determined frequency range, as well as the beta rhythm in the central, frontal and parietal EEG leads in children while performing tasks for instrumental, emotional and altruistic helping behavior. The study engaged 24 children aged 4 to 7 years. ANOVA showed a significant decrease of the mu rhythm amplitude in the central and parietal regions, which is supposed to be associated with the activation of the mirror system of the brain. When performing tasks for instrumental and altruistic helping behavior, there was an increase in the amplitude of the beta rhythm in the frontal, central, and parietal regions, which may be associated with children observing actions that are emotionally charged and cause empathy with a person in need of help. The more the beta rhythm increased, the sooner the children provided help, which can be explained by a greater degree of emotional involvement and activation of cognitive processes in children with high performance of prosocial behavior.

Особенности реактивности μ-ритма ЭЭГ у детей с расстройствами аутистического спектра в ситуациях помогающего поведения

One of the subjects being discussed by the professional community currently is the role possibly played by the mirror neuron system (MNS) in the violation of social behavior of children with autism spectrum disorders (ASD). The MNS is known to shape the perception of emotions of others and understanding and imitation of their actions. Mu rhythm desynchronization in EEG is considered to be the indicator of the MNS activation. The purpose of this study was to identify the features of reactivity of the EEG mu rhythm within an individually determined frequency range in preschoolers with ASD in situations requiring instrumental, emotional and altruistic helping behavior (HB). The study involved children 4–7 years old with ASD (n = 26) and their normally developing peers without the condition (n = 37). Although in most cases, HB was more pronounced in the group of normally developing children, the differences between the groups are significant only for altruistic HP (p < 0.01), and for the situation requiring complex altruistic and emotional HP it approaches significance (p = 0.09). Evaluation of the mu rhythm reactivity indices showed that the tasks invoking complex altruistic and emotional HB bring this indicator down significantly in children with ASD compared to the group of normally developing participants, as shown by the central leads of the left and right hemispheres and the parietal lead of the right hemisphere (C3: p = 0.02 ; C4: p = 0.03; P4: p = 0.03). It is assumed that the detected features stem from the impaired functioning of the MNS and the downstream regulation to the MNS from prefrontal cortex and other areas of the neocortex. The data obtained can be used in development of EEG biofeedback training protocols for children with ASD.

The effects of empathy by caregivers on healthcare service satisfaction.

Healthcare service satisfaction focuses not only on the patients but also on the caregivers’ perspectives. This study explored how caregivers’ empathy toward patients affects their satisfaction with healthcare services through an electroencephalography (EEG) experiment. EEG mu rhythm was used as the neural indicator to reflect empathy. The results showed that empathy reduces caregivers’ evaluation of healthcare service satisfaction because they share suffering with the patients. However, implementing physician–patient communication through a process-based informed consent (IC), compared to an event-based IC, can effectively alleviate such adverse effects.

EEG–EMG coupling as a hybrid method for steering detection in car driving settings

Understanding mental processes in complex human behavior is a key issue in driving, representing a milestone for developing user-centered assistive driving devices. Here, we propose a hybrid method based on electroencephalographic (EEG) and electromyographic (EMG) signatures to distinguish left and right steering in driving scenarios. Twenty-four participants took part in the experiment consisting of recordings of 128-channel EEG and EMG activity from deltoids and forearm extensors in non-ecological and ecological steering tasks. Specifically, we identified the EEG mu rhythm modulation correlates with motor preparation of self-paced steering actions in the non-ecological task, while the concurrent EMG activity of the left (right) deltoids correlates with right (left) steering. Consequently, we exploited the mu rhythm de-synchronization resulting from the non-ecological task to detect the steering side using cross-correlation analysis with the ecological EMG signals. Results returned significant cross-correlation values showing the coupling between the non-ecological EEG feature and the muscular activity collected in ecological driving conditions. Moreover, such cross-correlation patterns discriminate the steering side earlier relative to the single EMG signal. This hybrid system overcomes the limitation of the EEG signals collected in ecological settings such as low reliability, accuracy, and adaptability, thus adding to the EMG the characteristic predictive power of the cerebral data. These results prove how it is possible to complement different physiological signals to control the level of assistance needed by the driver.

Altering Facial Movements Abolishes Neural Mirroring of Facial Expressions

People tend to automatically imitate others’ facial expressions of emotion. That reaction, termed “facial mimicry” has been linked to sensorimotor simulation—a process in which the observer’s brain recreates and mirrors the emotional experience of the other person, potentially enabling empathy and deep, motivated processing of social signals. However, the neural mechanisms that underlie sensorimotor simulation remain unclear. This study tests how interfering with facial mimicry by asking participants to hold a pen in their mouth influences the activity of the human mirror neuron system, indexed by the desynchronization of the EEG mu rhythm. This response arises from sensorimotor brain areas during observed and executed movements and has been linked with empathy. We recorded EEG during passive viewing of dynamic facial expressions of anger, fear, and happiness, as well as nonbiological moving objects. We examine mu desynchronization under conditions of free versus altered facial mimicry and show that desynchronization is present when adult participants can freely move but not when their facial movements are inhibited. Our findings highlight the importance of motor activity and facial expression in emotion communication. They also have important implications for behaviors that involve occupying or hiding the lower part of the face.

НЕЙРОФИЗИОЛОГИЧЕСКИЕ МЕХАНИЗМЫ ВОСПРИЯТИЯ РЕЧИ И ИХ ОСОБЕННОСТИ У ДЕТЕЙ В НОРМЕ И ПРИ НАРУШЕНИЯХ РАЗВИТИЯ

Neuronal synchronization, reflected in the EEG pattern, is the mechanism by which the brain integrates different types of information contained in a speech message and presented in different areas of the brain (for example, phonological, spelling, semantic and syntactic information). The process of understanding a sentence consists of two groups of interrelated cognitive operations: it begins with searching in memory for phonological, syntactic and semantic properties of words, which is followed by integrating information into a general idea of the sentence meaning. The stage of searching for words in adults results in an increase in the theta rhythm power. The stage of integrating words into a sentence results in the growth of theta, beta, and gamma rhythms. At the same time, the growth of theta rhythm is more typical for children than for adults. Higher rhythms reactivity during speech perception indicates better developed speech skills in children. Under conditions of relative relaxation, the EEG of children with a high level of speech development is characterized by a moderate power level of theta and beta rhythms and a high level of alpha and mu rhythms. It is assumed that a key role in the process of understanding speech is played by the so-called «action perception circuits», surrounding the Sylvian sulcus of the left hemisphere. The «action perception circuits» are composed of nerve cells capable of providing the speech signals perception and generation. The most important subgroup of neurons included in the «action perception circuits» are mirror neurons that are activated when performing and observing actions. The desynchronization of the EEG mu rhythm is considered as mirror neurons activation marker. In several studies, it revealed that the level of mirror neurons activation and the level of speech understanding in children are connected. It is a topic of great interest to research the mu rhythm alpha and beta components reactivity both during the production of speech and during the perception of another person speech. At present, it is becoming obvious that analyzing the EEG rhythms power changes during the speech understanding in different scenarios could be used to identify the mechanisms of the brain language network and speech disorders. The revealed patterns make it possible to propose ways of correcting the children speech development using EEG biological feedback methods.

Enhanced mirroring upon mutual gaze: multimodal evidence from TMS-assessed corticospinal excitability and the EEG mu rhythm

Previous research has demonstrated that eye contact between actor and observer specifically enhances the ‘mirroring’ of others’ actions, as measured by transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs). However, it remains unknown whether other markers of mirror system activation, such as suppression of the EEG mu rhythm (8–13 Hz) over the sensorimotor strip, are also susceptible to perceived eye contact. Here, both TMS-induced MEPs and EEG mu suppression indices were assessed (in separate sessions) while 32 participants (mean age: 24y; 8m) observed a simple hand movement combined with direct or averted gaze from the actor. Both measures were significantly modulated by perceived eye gaze during action observation; showing an increase in MEP amplitude and an attenuation of the mu rhythm during direct vs. averted gaze. Importantly, while absolute MEP and mu suppression scores were not related, a significant association was identified between gaze-related changes in MEPs and mu suppression, indicating that both measures are similarly affected by the modulatory impact of gaze cues. Our results suggest that although the neural substrates underlying TMS-induced MEPs and the EEG mu rhythm may differ, both are sensitive to the social relevance of the observed actions, which might reflect a similar neural gating mechanism.

Mu rhythm separation from the mix with alpha rhythm: Principal component analyses and factor topography

BackgroundEEG mu rhythm suppression is assessed in experiments on the execution, observation and imagination of movements. It is utilised for studying of actions, language, empathy in healthy individuals and preservation of sensorimotor system functions in patients with schizophrenia and autism spectrum disorders. While EEG alpha and mu rhythms are recorded in the same frequency range (8−13 Hz), their specification becomes a serious issue. The new methodis based on the spatial and functional characteristics of the mu wave, which are: (1) the mu rhythm is located over the sensorimotor cortex; (2) it desynchronises during movement processing and does not respond on the eyes opening. In EEG recordings, we analysed the mu rhythm under conditions with eyes opened and eyes closed (baseline), and during a motor imagery task with eyes closed. EEG recordings were processed by principal component analysis (PCA). ResultsThe analysis of EEG data with the proposed approach revealed the maximum spectral power of mu rhythm localised in the sensorimotor areas. During motor imagery, mu rhythm was suppressed more in frontal and central sites than in occipital sites, whereas alpha rhythm was suppressed more in parietal and occipital sites. Mu rhythm desynchronization in sensorimotor sites during motor imagery was greater than alpha rhythm desynchronization.The proposed method enabled EEG mu rhythm separation from its mix with alpha rhythm. ConclusionsEEG mu rhythm separation with the proposed method satisfies its classical definition.

I'll cry instead: Mu suppression responses to tearful facial expressions

Tears are a facial expression of emotion that readily elicit empathic responses from observers. It is currently unknown whether these empathic responses to tears are influenced by specific neural substrates. The EEG mu rhythm is one method of investigating the human mirror neuron system, purported to underlie the sharing of affective states and a facilitator of social cognition. The purpose of this research was to explore the mu response to tearful expressions of emotion. Sixty-eight participants viewed happy and sad faces, both with and without tears, in addition to a neutral control condition. Participants first completed an emotion discrimination task, and then an imitation condition where they were required to mimic the displayed expression. Mu enhancement was found in response to the discrimination task, whilst suppression was demonstrated in response to the imitation condition. Examination of the suppression scores revealed that greater suppression was observed in response to happy-tear and sad tear-free expressions. Planned contrasts exploring suppression to neutral faces revealed no significant differences between emotional and neutral conditions. The mu response to neutral expressions resembled that of the happy-tear and the sad tear-free conditions, lending support to the idea that ambiguous emotional expressions require greater sensorimotor engagement. This study provides preliminary evidence for the role of the mirror neuron system in discerning tearful expressions of emotion in the absence of context.

Intranasal oxytocin enhances EEG mu rhythm desynchronization during execution and observation of social action: An exploratory study

Intranasal administration of oxytocin (OT) has been found to facilitate prosocial behaviors, emotion recognition and cooperation between individuals. Recent electroencephalography (EEG) investigations have reported enhanced mu rhythm (alpha: 8–13 Hz; beta: 15–25 Hz) desynchronization during the observation of biological motion and stimuli probing social synchrony after the administration of intranasal OT. This hormone may therefore target a network of cortical circuits involved in higher cognitive functions, including the mirror neuron system (MNS). Here, in a double-blind, placebo-controlled, between-subjects exploratory study, we investigated whether intranasal OT modulates the cortical activity from sensorimotor areas during the observation and the execution of social and non-social grasping actions. Participants underwent EEG testing after receiving a single dose (24 IU) of either intranasal OT or placebo. Results revealed an enhancement of alpha - but not beta - desynchronization during observation and execution of social grasps, especially over central and parietal electrodes, in participants who received OT (OT group). No differences between the social and non-social condition were found in the control group (CTRL group). Moreover, we found a significant difference over the cortical central-parietal region between the OT and CTRL group only within the social condition. These results suggest a possible action of intranasal OT on sensorimotor circuits involved in social perception and action understanding, which might contribute to facilitate the prosocial effects typically reported by behavioral studies.

Exploring the EEG mu rhythm associated with observation and execution of a goal-directed action in 14-month-old preterm infants

Electroencephalographic mu rhythm desynchronization is thought to reflect Mirror Neuron System (MNS) activity and represents an important neural correlate of the coupling between action execution and perception. It is still unclear if the MNS in human ontogeny is already available at the beginning of postnatal life and how early experience impacts its development. Premature birth provides a “natural condition” for investigating the effects of early, atypical extra-uterine experience on MNS. The main aim of the present study was to investigate whether the MNS activity is associated with prematurity. We compared the mu rhythm activity in preterm (PT) and full-term (FT) 14-month old infants during an action observation/execution (AO/AE) task. Mu rhythm desynchronization was computed over frontal, central, parietal and occipital regions. Both groups showed mu rhythm suppression in all the scalp regions during action execution. Different desynchronization patterns emerged during action observation. Specifically, FT infants showed mu suppression in the right frontal, bilateral parietal and occipital regions; whereas PT infants exhibited mu suppression only in the right parietal region. Overall, these preliminary findings indicate that an atypical extra uterine experience might have an impact on the MNS activity.

Both the mirror and the affordance systems might be impaired in adults with high autistic traits. Evidence from EEG mu and beta rhythms.

The association of autism spectrum disorder (ASD) with an altered mirror neuron system is still controversial. At the same time, the processing of object affordances by persons with ASD is a neglected issue. In this electroencephalographic study, adults differing in their autism quotient (AQ) scores were selected. We found anomalous modulation of mu and beta rhythms in high-AQ, compared to low-AQ persons, while they watched a set of goal-directed manual actions. This confirms that observing actions involving implicit intentions most clearly reveals the impairment of the mirror neurons system (MNS). The high-AQ group also showed anomalous mu and beta modulation when they looked at pictures of manipulable objects, indicating a deficit in processing motor affordances. We conclude that high-AQ adults have neural impairment of both the MNS and the affordance systems, which could underlie their relational problems with both people and objects. Autism Res 2019, 12: 1032-1042. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Adults with autistic traits (high-autism quotient [AQ] scores) and matched controls (low-AQ) observed intentional hand actions, and pictures of manipulable and non-manipulable objects. The high-AQ group compared to the control group, showed anomalous modulation of the electroencephalographic motoric rhythms (mu and beta) while observing familiar goal-directed actions, confirming an impairment of their mirror neuron system. Also, their brain rhythms were anomalous when they watched manipulable objects, which suggest a dysfunction in their relation with objects (affordance system).

Возрастная динамика и топография реактивности индивидуального мю-ритма ЭЭГ у детей 4–14 лет

Возрастная динамика и топография реактивности индивидуального мю-ритма ЭЭГ у детей 4–14 лет

Mu Suppression Is Sensitive to Observational Practice but Results in Different Patterns of Activation in Comparison with Physical Practice.

Research has shown the effectiveness of observational practice for motor learning, but there continues to be debate about the mechanisms underlying effectiveness. Although cortical processes can be moderated during observation, after both physical and observational practice, how these processes change with respect to behavioural measures of learning has not been studied. Here we compared short-term physical and observational practice during the acquisition and retention of a novel motor task to evaluate how each type of practice modulates EEG mu rhythm (8–13 Hz). Thirty healthy individuals were randomly assigned to one of three groups: (1) physical practice (PP), (2) observational practice (OP), and (3) no practice (NP) control. There were four testing stages: baseline EEG, practice, postpractice observation, and delayed retention. There was significant bilateral suppression of mu rhythm during PP but only left lateralized mu suppression during OP. In the postpractice observation phase, mu suppression was bilateral and larger after PP compared to that after OP. NP control showed no evidence of suppression and was significantly different to both the OP and PP groups. When comparing the three groups in retention, the groups did not differ with respect to tracing times, but the PP group showed fewer errors, especially in comparison to the NP group. Therefore, although the neurophysiological measures index changes in the OP group, which are similar but moderated in comparison to PP, changes in these processes are not manifest in observational practice outcomes when assessed in a delayed retention test.

Suppression of EEG mu rhythm during action observation corresponds with subsequent changes in behavior

Movement is intrinsically linked to perception such that observing an action induces in the observer behavioral changes during execution of similar actions. Electroencephalogram (EEG) studies have revealed that at the group level, action observation suppresses oscillatory power in mu (8–12 Hz) and beta (15–25 Hz) bands over the sensorimotor cortex – a phenomenon associated with increased excitability of cortical neurons. However, it is unclear whether differences in suppression level across individuals is linked with individual differences in subsequent behavioral changes. Here 32 subjects performed self-paced finger tapping with their right hand before and after observation of a video displaying finger-tapping at either 2 or 4 Hz. Behaviorally, subjects’ rate of self-pace tapping increased following observation, with higher increases following 4 Hz observation. The level of EEG power suppression in the low frequency range (low mu; 8–10 Hz) during observation corresponded to subsequent behavioral changes in tapping rate across individuals. Our results demonstrate that observing actions implicitly shifts subsequent execution rates, and that individual differences in the level of this implicit shift can be explained by activity in the sensorimotor cortex during observation.

The Effects of Fluency Enhancing Conditions on Sensorimotor Control of Speech in Typically Fluent Speakers: An EEG Mu Rhythm Study.

Objective: To determine whether changes in sensorimotor control resulting from speaking conditions that induce fluency in people who stutter (PWS) can be measured using electroencephalographic (EEG) mu rhythms in neurotypical speakers.Methods: Non-stuttering (NS) adults spoke in one control condition (solo speaking) and four experimental conditions (choral speech, delayed auditory feedback (DAF), prolonged speech and pseudostuttering). Independent component analysis (ICA) was used to identify sensorimotor μ components from EEG recordings. Time-frequency analyses measured μ-alpha (8–13 Hz) and μ-beta (15–25 Hz) event-related synchronization (ERS) and desynchronization (ERD) during each speech condition.Results: 19/24 participants contributed μ components. Relative to the control condition, the choral and DAF conditions elicited increases in μ-alpha ERD in the right hemisphere. In the pseudostuttering condition, increases in μ-beta ERD were observed in the left hemisphere. No differences were present between the prolonged speech and control conditions.Conclusions: Differences observed in the experimental conditions are thought to reflect sensorimotor control changes. Increases in right hemisphere μ-alpha ERD likely reflect increased reliance on auditory information, including auditory feedback, during the choral and DAF conditions. In the left hemisphere, increases in μ-beta ERD during pseudostuttering may have resulted from the different movement characteristics of this task compared with the solo speaking task. Relationships to findings in stuttering are discussed.Significance: Changes in sensorimotor control related feedforward and feedback control in fluency-enhancing speech manipulations can be measured using time-frequency decompositions of EEG μ rhythms in neurotypical speakers. This quiet, non-invasive, and temporally sensitive technique may be applied to learn more about normal sensorimotor control and fluency enhancement in PWS.

Analysis of Electroencephalography Event-Related Desynchronisation and Synchronisation Induced by Lower-Limb Stepping Motor Imagery

Bilateral upper-limb motor imagery has been demonstrated to be a useful mental task in electroencephalography (EEG)-based brain–computer interfaces (BCIs). By contrast, few studies have examined bilateral lower-limb motor imagery, and all of them have focused on imaginary foot movements. The left–right classification accuracy reported in these studies based on the EEG mu rhythm (8–13 Hz) and beta band (13–30 Hz) remains unsatisfactory. The present study investigated the possibility of using lower-limb stepping motor imagery as the mental task and analysed the EEG difference between imaginary left-leg stepping (L-stepping) and right-leg stepping (R-stepping) movements. An experimental paradigm was designed to collect 5-s motor imagery EEG signals at nine recording sites around the vertex of the brain. Results from eight able-bodied participants indicated that the commonly used mu event-related desynchronisation (ERD) feature exhibited no significant difference between the two imaginary movements for all recording sites and all time intervals within the 5-s motor imagery period. Regarding the other commonly used feature, beta event-related synchronisation, no significant difference between the two imagery tasks was observed for most of the recording sites and time intervals. Instead, theta band (4–8 Hz) ERD significantly differed between the L- and R-stepping imagery tasks at five sites (FC4, C3, CP3, Cz, CPz) within the first 2 s after motor imagery cue onset. The findings from the present study may be a basis for further development of BCI systems for decoding left and right stepping during mental exercise where the two motions are alternately imagined.

Social reward in action: Reward magnitude and valence effects on the EEG mu rhythm

Social reward in action: Reward magnitude and valence effects on the EEG mu rhythm

Trait related sensorimotor deficits in people who stutter: An EEG investigation of μ rhythm dynamics during spontaneous fluency.

Stuttering is associated with compromised sensorimotor control (i.e., internal modeling) across the dorsal stream and oscillations of EEG mu (μ) rhythms have been proposed as reliable indices of anterior dorsal stream processing. The purpose of this study was to compare μ rhythm oscillatory activity between (PWS) and matched typically fluent speakers (TFS) during spontaneously fluent overt and covert speech production tasks. Independent component analysis identified bilateral μ components from 24/27 PWS and matched TFS that localized over premotor cortex. Time-frequency analysis of the left hemisphere μ clusters demonstrated significantly reduced μ-α and μ-β ERD (pCLUSTER < 0.05) in PWS across the time course of overt and covert speech production, while no group differences were found in the right hemisphere in any condition. Results were interpreted through the framework of State Feedback Control. They suggest that weak forward modeling and evaluation of sensory feedback across the time course of speech production characterizes the trait related sensorimotor impairment in PWS. This weakness is proposed to represent an underlying sensorimotor instability that may predispose the speech of PWS to breakdown.