Classification of Targets and Distractors in an Audiovisual Attention Task Based on Electroencephalography.

Within the broader context of improving interactions between artificial intelligence and humans, the question has arisen regarding whether auditory and rhythmic support could increase attention for visual stimuli that do not stand out clearly from an information stream. To this end, we designed an experiment inspired by pip-and-pop but more appropriate for eliciting attention and P3a-event-related potentials (ERPs). In this study, the aim was to distinguish between targets and distractors based on the subject's electroencephalography (EEG) data. We achieved this objective by employing different machine learning (ML) methods for both individual-subject (IS) and cross-subject (CS) models. Finally, we investigated which EEG channels and time points were used by the model to make its predictions using saliency maps. We were able to successfully perform the aforementioned classification task for both the IS and CS scenarios, reaching classification accuracies up to 76%. In accordance with the literature, the model primarily used the parietal-occipital electrodes between 200 ms and 300 ms after the stimulus to make its prediction. The findings from this research contribute to the development of more effective P300-based brain-computer interfaces. Furthermore, they validate the EEG data collected in our experiment.

Neural entrainment underpins sensorimotor synchronization to dynamic rhythmic stimuli.

Neural entrainment, defined as unidirectional synchronization of neural oscillations to an external rhythmic stimulus, is a topic of major interest in the field of neuroscience. Despite broad scientific consensus on its existence, on its pivotal role in sensory and motor processes, and on its fundamental definition, empirical research struggles in quantifying it with non-invasive electrophysiology. To this date, broadly adopted state-of-the-art methods still fail to capture the dynamic underlying the phenomenon. Here, we present event-related frequency adjustment (ERFA) as a methodological framework to induce and to measure neural entrainment in human participants, optimized for multivariate EEG datasets. By applying dynamic phase and tempo perturbations to isochronous auditory metronomes during a finger-tapping task, we analyzed adaptive changes in instantaneous frequency of entrained oscillatory components during error correction. Spatial filter design allowed us to untangle, from the multivariate EEG signal, perceptual and sensorimotor oscillatory components attuned to the stimulation frequency. Both components dynamically adjusted their frequency in response to perturbations, tracking the stimulus dynamics by slowing down and speeding up the oscillation over time. Source separation revealed that sensorimotor processing enhanced the entrained response, supporting the notion that the active engagement of the motor system plays a critical role in processing rhythmic stimuli. In the case of phase shift, motor engagement was a necessary condition to observe any response, whereas sustained tempo changes induced frequency adjustment even in the perceptual oscillatory component. Although the magnitude of the perturbations was controlled across positive and negative direction, we observed a general bias in the frequency adjustments towards positive changes, which points at the effect of intrinsic dynamics constraining neural entrainment. We conclude that our findings provide compelling evidence for neural entrainment as mechanism underlying overt sensorimotor synchronization, and highlight that our methodology offers a paradigm and a measure for quantifying its oscillatory dynamics by means of non-invasive electrophysiology, rigorously informed by the fundamental definition of entrainment.

Reducing the peak tibial acceleration of running by music-based biofeedback: A quasi-randomized controlled trial.

BACKGROUND: Running retraining with the use of biofeedback on an impact measure has been executed or evaluated in the biomechanics laboratory. Here, the execution and evaluation of feedback-driven retraining are taken out of the laboratory. PURPOSE: To determine whether biofeedback can reduce the peak tibial acceleration with or without affecting the running cadence in a 3-week retraining protocol. STUDY DESIGN: Quasi-randomized controlled trial. METHODS: Twenty runners with high peak tibial acceleration were allocated to either the retraining (n = 10, 32.1 ± 7.8 years, 10.9 ± 2.8 g) or control (n = 10, 39.1 ± 10.4 years, 13.0 ± 3.9 g) groups. They performed six running sessions in an athletic training environment. A body-worn system collected axial tibial acceleration and provided real-time feedback. The retraining group received music-based biofeedback in a faded feedback scheme. Pink noise was superimposed on tempo-synchronized music when the peak tibial acceleration was ≥70% of the runner's baseline. The control group received tempo-synchronized music, which acted as a placebo for blinding purposes. Speed feedback was provided to obtain a stable running speed of ~2.9 m·s-1 . Peak tibial acceleration and running cadence were evaluated. RESULTS: A significant group-by-feedback interaction effect was detected for peak tibial acceleration. The experimental group had a decrease in peak tibial acceleration by 25.5% (mean: 10.9 ± 2.8 g versus 8.1 ± 3.9 g, p = 0.008, d = 1.08, mean difference = 2.77 [0.94, 4.61]) without changing the running cadence. The control group had no statistically significant change in peak tibial acceleration nor in running cadence. CONCLUSION: The retraining protocol was effective at reducing the peak tibial acceleration in high-impact runners by reacting to music-based biofeedback that was provided in real time per wearable technology in a training environment. This reduction magnitude may have meaningful influences on injury risk.

Music-based biofeedback to reduce tibial shock in over-ground running: a proof-of-concept study.

Methods to reduce impact in distance runners have been proposed based on real-time auditory feedback of tibial acceleration. These methods were developed using treadmill running. In this study, we extend these methods to a more natural environment with a proof-of-concept. We selected ten runners with high tibial shock. They used a music-based biofeedback system with headphones in a running session on an athletic track. The feedback consisted of music superimposed with noise coupled to tibial shock. The music was automatically synchronized to the running cadence. The level of noise could be reduced by reducing the momentary level of tibial shock, thereby providing a more pleasant listening experience. The running speed was controlled between the condition without biofeedback and the condition of biofeedback. The results show that tibial shock decreased by 27% or 2.96 g without guided instructions on gait modification in the biofeedback condition. The reduction in tibial shock did not result in a clear increase in the running cadence. The results indicate that a wearable biofeedback system aids in shock reduction during over-ground running. This paves the way to evaluate and retrain runners in over-ground running programs that target running with less impact through instantaneous auditory feedback on tibial shock.

Detrended fluctuation analysis of gait dynamics when entraining to music and metronomes at different tempi in persons with multiple sclerosis.

In persons with multiple sclerosis (PwMS), synchronizing walking to auditory stimuli such as to music and metronomes have been shown to be feasible, and positive clinical effects have been reported on step frequency and perception of fatigue. Yet, the dynamic interaction during the process of synchronization, such as the coupling of the steps to the beat intervals in music and metronomes, and at different tempi remain unknown. Understanding these interactions are clinically relevant, as it reflects the pattern of step intervals over time, known as gait dynamics. 28 PwMS and 29 healthy controls were instructed to walk to music and metronomes at 6 tempi (0-10% in increments of 2%). Detrended fluctuation analysis was applied to calculate the fractal statistical properties of the gait time-series to quantify gait dynamics by the outcome measure alpha. The results showed no group differences, but significantly higher alpha when walking to music compared to metronomes, and when walking to both stimuli at tempi + 8, + 10% compared to lower tempi. These observations suggest that the precision and adaptation gain differ during the coupling of the steps to beats in music compared to metronomes (continuous compared to discrete auditory structures) and at different tempi (different inter-beat-intervals).

The sonic instructor: A music-based biofeedback system for improving weightlifting technique.

In this study, we assumed that correct functional movements for weightlifting can be learned with the help of a music-based biofeedback system. We compared musical feedback with verbal feedback from experienced trainers using two independent groups. The focus was on one specific movement called deadlift. Physical parameters under considerations were the spine (i.e. loss of midline stability resulting in flexion) and the forward displacement of the barbell during the repetitions relative to the mid-foot. We recruited 31 recreational weight lifters (21-42 years of age). Results revealed that both feedback types are effective in improving the movements for deadlift. No significant differences were found across the two feedback types, neither in terms of movement, nor in terms of clarity and motivation. The results suggest that the proposed feedback system is a valid tool for technology-aided training and self-training practices.

The role of interaction and predictability in the spontaneous entrainment of movement.

People walking side by side spontaneously synchronize their steps on some occasions but not on others, which poses a challenge to theories of perception-action based on interactive dynamic systems. How can action be spontaneously entrained by some sources of perceptual information while others are selectively ignored? The predictive processing framework suggests that saliency factors such as stimulus predictability, consistent deviation, and interactivity of the stimulus control the coupling between the motor system and perceptual information. To test this, we compared entrainment of gait cadence by two interactive auditory stimuli and two noninteractive but predictable, faster than preferred stimuli that were isochronous or statistically matched to gait. One interactive stimulus had properties that are optimal for mutual entrainment as per a mathematical model of interactive periodic processes, the Kuramoto system. In particular, the stimulus was faster than the participant but also adapted its rate to a limited degree as function of phase mismatch with the participant's steps. The second interactive stimulus fully mirrored the gait cycle hence it did not induce mutual synchronization. Furthermore, healthy participants were compared to ones with impaired gait due to Parkinson's disease, a model disorder that makes movement more dependent on external cueing. The mutually interactive condition produced the strongest entrainment, in patients and healthy participants, without differences between groups. The stimulus adapted to each participant's gait while maintaining a consistent lead in phase. Auditory-motor coupling may be enhanced by stimuli that are not only predictable but also interactive in that they align to self-generated movements. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Walking to Music and Metronome at Various Tempi in Persons With Multiple Sclerosis: A Basis for Rehabilitation.

Background. Mobility dysfunctions are prevalent in persons with multiple sclerosis (PwMS), thus novel rehabilitation mechanisms are needed toward functional training. The effect of auditory cueing is well-known in Parkinson's disease, yet the application of different types of auditory stimuli at different tempi has not been investigated yet. Objectives. Investigating if PwMS, compared with healthy controls (HC), can synchronize their gait to music and metronomes at different tempi during walking and the effects of the stimuli on perceived fatigue and gait. Additionally, exploring if cognitive impairment would be a factor on the results. Methods. The experimental session consisted of 2 blocks, music and metronomes. Per block, participants walked 3 minutes per tempi, with instructions to synchronize their steps to the beat. The tempi were 0%, +2%, +4% +6%, +8%, +10% of preferred walking cadence (PWC). Results. A total of 28 PwMS and 29 HC participated. On average, participants were able to synchronize at all tempi to music and metronome. Higher synchronization was obtained for metronomes compared with music. The highest synchronization for music was found between +2% and +8% of PWC yet pwMS perceived less physical and cognitive fatigue walking to music compared with metronomes. Cognitive impaired PwMS (n = 9) were not able to synchronize at tempi higher than +6%. Conclusion. Auditory-motor coupling and synchronization was feasible in HC and PwMS with motor and cognitive impairments. PwMS walked at higher tempi than their preferred walking cadence, and lower fatigue perception with music. Coupling walking to music could be a promising functional walking training strategy.

Validity and reliability of peak tibial accelerations as real-time measure of impact loading during over-ground rearfoot running at different speeds.

Studies seeking to determine the effects of gait retraining through biofeedback on peak tibial acceleration (PTA) assume that this biometric trait is a valid measure of impact loading that is reliable both within and between sessions. However, reliability and validity data were lacking for axial and resultant PTAs along the speed range of over-ground endurance running. A wearable system was developed to continuously measure 3D tibial acceleration and to detect PTAs in real-time. Thirteen rearfoot runners ran at 2.55, 3.20 and 5.10 m·s-1 over an instrumented runway in two sessions with re-attachment of the system. Intraclass correlation coefficients (ICCs) were used to determine within-session reliability. Repeatability was evaluated by paired T-tests and ICCs. Concerning validity, axial and resultant PTAs were correlated to the peak vertical impact loading rate (LR) of the ground reaction force. Additionally, speed should affect impact loading magnitude. Hence, magnitudes were compared across speeds by RM-ANOVA. Within a session, ICCs were over 0.90 and reasonable for clinical measurements. Between sessions, the magnitudes remained statistically similar with ICCs ranging from 0.50 to 0.59 for axial PTA and from 0.53 to 0.81 for resultant PTA. Peak accelerations of the lower leg segment correlated to LR with larger coefficients for axial PTA (r range: 0.64-0.84) than for the resultant PTA per speed condition. The magnitude of each impact measure increased with speed. These data suggest that PTAs registered per stand-alone system can be useful during level, over-ground, rearfoot running to evaluate impact loading in the time domain when force platforms are unavailable in studies with repeated measurements.

A model of different cognitive processes during spontaneous and intentional coupling to music in multiple sclerosis.

Evidence for using auditory-motor coupling in neurological rehabilitation to facilitate walking is increasing. However, the distinction between spontaneous and intended coupling and its underlying mechanisms is yet to be investigated. In this study, we include 30 persons with multiple sclerosis and 30 healthy controls (HCs) in an experiment with two sessions in which participants were asked to walk to music with various tempi, matching their preferred walking cadence (PWC) up to 10% above in incremental steps of 2%. In the first session, no instructions were given to synchronize. In the second, participants were instructed to synchronize steps to the beats. Spontaneous synchronization was possible at 0% and +2% of the PWC, and fewer persons with multiple sclerosis were able to do so compared with HCs. Instruction was needed to synchronize at above +2% tempo in all participants. In the instructed session, the +6% condition marked a cutoff for cognitively impaired persons, as they were no longer able to synchronize. Based on our findings, we constructed a model illustrating that spontaneous entrainment is limited, operating during spontaneous coupling at only 0% and +2% of the PWC, and that at a higher tempo, entrainment requires intentional synchronization, with an active cognitive control mechanism.

Effectiveness of music-based interventions on motricity or cognitive functioning in neurological populations: a systematic review.

BACKGROUND: Motor and cognitive symptoms are frequent in persons with neurological disorders and often require extensive long-term rehabilitation. Recently, a variety of music-based interventions have been introduced into neurological rehabilitation as training tools. EVIDENCE ACQUISITION: This review aims to 1) describe and define music-based intervention modalities and content which are applied in experimental studies; and 2) describe the effects of these interventions on motor and/or cognitive symptoms in the neurological population. The databases PubMed and Web of Science were searched. Cited references of included articles where screened for potential inclusion. A systematic literature search up to 20th of June 2016 was conducted to include controlled trials and cohort studies that have used music-based interventions for ≥3 weeks in the neurological population (in- and outpatients) targeting motor and/or cognitive symptoms. No limitations to publication date was set. EVIDENCE SYNTHESISː Nineteen articles comprising thirteen randomized controlled trials (total participants Nexp=241, Nctrl=269), four controlled trials (Nexp=59, Nctrl=53) and two cohort studies (N.=27) were included. Fourteen studies were conducted in stroke, three in Parkinson's disease, and two in multiple sclerosis population. Modalities of music-based interventions were clustered into four groups: instrument-based, listening-based, rhythm-based, and multicomponent-based music interventions. Overall, studies consistently showed that music-based interventions had similar or larger effects than conventional rehabilitation on upper limb function (N.=16; fine motricity, hand and arm capacity, finger and hand tapping velocity/variability), mobility (N.=7; gait parameters), and cognition (N.=4; verbal memory and focused attention). CONCLUSIONSː Variety of modalities using music-based interventions has been identified and grouped into four clusters. Effects of interventions demonstrate an improvement in the domains assessed. Evidence is most available for improving motricity in stroke. More studies are warranted to investigate cognition as well as motor and cognition dysfunctions in combination. Instrument-based music interventions can improve fine motor dexterity and gross motor functions in stroke. Rhythm-based music interventions can improve gait parameters of velocity and cadence in stroke, Parkinson's disease and multiple sclerosis. Cognition in the domains of verbal memory and focused attention can improve after listening-based music interventions in stroke.

Alignment strategies for the entrainment of music and movement rhythms.

Theories of entrainment assume that spontaneous entrainment emerges from dynamic laws that operate via mediators on interactions, whereby entrainment is facilitated if certain conditions are fulfilled. In this study, we show that mediators can be built that affect the entrainment of human locomotion to music. More specifically, we built D-Jogger, a music player that functions as a mediator between music and locomotion rhythms. The D-Jogger makes it possible to manipulate the timing differences between salient moments of the rhythms (beats and footfalls) through the manipulation of the musical period and phase, which affect the condition in which entrainment functions. We conducted several experiments to explore different strategies for manipulating the entrainment of locomotion and music. The results of these experiments showed that spontaneous entrainment can be manipulated, thereby suggesting different strategies on how to embark. The findings furthermore suggest a distinction among different modalities of entrainment: finding the beat (the most difficult part of entrainment), keeping the beat (easier, as a temporal scheme has been established), and being in phase (no entrainment is needed because the music is always adapted to the human rhythm). This study points to a new avenue of research on entrainment and opens new perspectives for the neuroscience of music.

Encouraging spontaneous synchronisation with D-Jogger, an adaptive music player that aligns movement and music.

In this study we explore how music can entrain human walkers to synchronise to the musical beat without being instructed to do so. For this, we use an interactive music player, called D-Jogger, that senses the user's walking tempo and phase. D-Jogger aligns the music by manipulating the timing difference between beats and footfalls. Experiments are reported that led to the development and optimisation of four alignment strategies. The first strategy matched the music's tempo continuously to the runner's pace. The second strategy matched the music's tempo at the beginning of a song to the runner's pace, keeping the tempo constant for the remainder of the song. The third alignment starts a song in perfect phase synchrony and continues to adjust the tempo to match the runner's pace. The fourth and last strategy additionally adjusts the phase of the music so each beat matches a footfall. The first two strategies resulted in a minor increase of steps in phase synchrony with the main beat when compared to a random playlist, the last two strategies resulted in a strong increase in synchronised steps. These results may be explained in terms of phase-error correction mechanisms and motor prediction schemes. Finding the phase-lock is difficult due to fluctuations in the interaction, whereas strategies that automatically align the phase between movement and music solve the problem of finding the phase-locking. Moreover, the data show that once the phase-lock is found, alignment can be easily maintained, suggesting that less entrainment effort is needed to keep the phase-lock, than to find the phase-lock. The different alignment strategies of D-Jogger can be applied in different domains such as sports, physical rehabilitation and assistive technologies for movement performance.

Expressive body movement responses to music are coherent, consistent, and low dimensional.

Embodied music cognition stresses the role of the human body as mediator for the encoding and decoding of musical expression. In this paper, we set up a low dimensional functional model that accounts for 70% of the variability in the expressive body movement responses to music. With the functional principal component analysis, we modeled individual body movements as a linear combination of a group average and a number of eigenfunctions. The group average and the eigenfunctions are common to all subjects and make up what we call the commonalities. An individual performance is then characterized by a set of scores (the individualities), one score per eigenfunction. The model is based on experimental data which finds high levels of coherence/consistency between participants when grouped according to musical education. This shows an ontogenetic effect. Participants without formal musical education focus on the torso for the expression of basic musical structure (tempo). Musically trained participants decode additional structural elements in the music and focus on body parts having more degrees of freedom (such as the hands). Our results confirm earlier studies that different body parts move differently along with the music.

Activating and relaxing music entrains the speed of beat synchronized walking.

Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musical stimuli all having a tempo of 130 beats per minute and a meter of 4 beats. The walking speed was measured as the walked distance during a time interval of 30 seconds. The results reveal that some music is 'activating' in the sense that it increases the speed, and some music is 'relaxing' in the sense that it decreases the speed, compared to the spontaneous walked speed in response to metronome stimuli. Participants are consistent in their observation of qualitative differences between the relaxing and activating musical stimuli. Using regression analysis, it was possible to set up a predictive model using only four sonic features that explain 60% of the variance. The sonic features capture variation in loudness and pitch patterns at periods of three, four and six beats, suggesting that expressive patterns in music are responsible for the effect. The mechanism may be attributed to an attentional shift, a subliminal audio-motor entrainment mechanism, or an arousal effect, but further study is needed to figure this out. Overall, the study supports the hypothesis that recurrent patterns of fluctuation affecting the binary meter strength of the music may entrain the vigor of the movement. The study opens up new perspectives for understanding the relationship between entrainment and expressiveness, with the possibility to develop applications that can be used in domains such as sports and physical rehabilitation.

Anatomical differences in the human inferior colliculus relate to the perceived valence of musical consonance and dissonance.

Helmholtz himself speculated about a role of the cochlea in the perception of musical dissonance. Here we indirectly investigated this issue, assessing the valence judgment of musical stimuli with variable consonance/dissonance and presented diotically (exactly the same dissonant signal was presented to both ears) or dichotically (a consonant signal was presented to each ear--both consonant signals were rhythmically identical but differed by a semitone in pitch). Differences in brain organisation underlying inter-subject differences in the percept of dichotically presented dissonance were determined with voxel-based morphometry. Behavioral results showed that diotic dissonant stimuli were perceived as more unpleasant than dichotically presented dissonance, indicating that interactions within the cochlea modulated the valence percept during dissonance. However, the behavioral data also suggested that the dissonance percept did not depend crucially on the cochlea, but also occurred as a result of binaural integration when listening to dichotic dissonance. These results also showed substantial between-participant variations in the valence response to dichotic dissonance. These differences were in a voxel-based morphometry analysis related to differences in gray matter density in the inferior colliculus, which strongly substantiated a key role of the inferior colliculus in consonance/dissonance representation in humans.