Participants
A total of thirty participants were randomly divided into two groups: the Music (n=15) and Control (n=15) groups. There were no statistical differences between the two groups in gender, age, height, body mass, and body mass index (BMI) (Table 1). They are all right-handed by self-report and have no special music experience. It was essential that participants did not have any neurological disorders, which could influence brain function. Additionally, all participants were required to have normal hearing capabilities, with no hearing impairments. Prior to the experiment, all participants provided informed consent. The protocol, including the selection criteria and the experimental conditions, was approved by this university ethical review board.
Table 1 Demographic data of participants
|
Music (n=15)
|
Control (n=15)
|
t/x2
|
P value
|
Gender (male/female)
|
8/7
|
10/5
|
0.556
|
0.456
|
Age (years)
|
22.2±2.0
|
21.6±2.7
|
0.611
|
0.545
|
Height (cm)
|
167.0±7.8
|
169.9±9.0
|
0.925
|
0.362
|
Body mass(kg)
|
63.4±9.5
|
67.4±11.4
|
1.029
|
0.312
|
BMI (kg/m2)
|
22.6±1.7
|
23.1±1.8
|
0.796
|
0.432
|
Educations (years)
|
15.2±1.5
|
14.5±2.3
|
1.000
|
0.325
|
Experimental Design
In this study, a randomized controlled design was implemented, comprising two groups: the Music and Control groups. The experiment encompassed three testing sessions. The initial session served as the baseline assessment, followed by the induction of mental fatigue in the second session, and finally, the music intervention in the third session. During the baseline assessment, data collection included the Visual Analog Scale (VAS) and resting-state EEG. In the second session, mental fatigue was induced through a 30-minute Stroop task, followed by assessment using the VAS and EEG power spectrum analysis. Subsequently, in the third session, participants engaged in either a 20-minute music session or remained in silence after mental fatigue, depending on group assignment. The same evaluations of VAS and 3-min EEG collection were conducted following the intervention. The music chosen for the intervention aimed to provide a pleasant and engaging auditory experience. Participants in the Control group experienced silence after mental fatigue, without specific auditory stimuli. The experimental setup is illustrated in Fig. 1.
Experimental Procedure
Baseline Assessment
Firstly, a 3-min resting-state EEG signals with eyes closed were recorded and then the VAS was assessed, to test whether there were significant differences in degrees of mental fatigue and EEG power spectrum in baseline state.
Induction of Mental Fatigue Based on Stroop Task
In this study, the Stroop task served as the method to induce mental fatigue. The task involved displaying colored words on a computer screen using E-prime 3.0 software, prompting participants to respond based on the color of the word presented. Two conditions were included: congruent and incongruent. In the congruent condition, the color names matched the color displayed (e.g., the word "red" presented in red color). Conversely, in the incongruent condition, the color names did not correspond to the color displayed (e.g., the word "red" displayed in blue color). Following the protocol outlined by Niu et al. (2024), in this study the incongruent condition was utilized to induce mental fatigue. In this condition, participants were tasked with swiftly and accurately identifying the color of the word, disregarding the word itself. The Stroop task was continuously administered for duration of 30 minutes. Participants' fatigue levels were monitored using the VAS, while accuracy and reaction time during the Stroop task were recorded for analysis.
Music Intervention
During the music listening phase, participants were instructed to spend 20 minutes seated in front of a black screen while listening to enjoyable music. The selection of relaxing music was sourced from functional music curated by the China Institute of Sport Science, which had been utilized to assist Chinese athletes in alleviating mental fatigue during their preparation for the Olympic Games. The music was played through a power amplifier connected to a computer system. To maintain consistent volume levels, music software was employed to set the volume at 50 dB and ensure a tempo ranging from 65 to 80 beats per minute. All participants were exposed to the same set of eight instrumental folk music pieces following the fatigue-inducing task. Conversely, participants in the control group engaged in a 20-minute seated rest period.
Data Collection and Analysis
Behavioral Data Collection and Analysis
Reaction time and error rate were measured as behavioral variables via E-prime 3.0 (Psychology Software Tools, Pittsburgh, PA, USA).
Subjective Data Collection and Analysis
The VAS serves as a widely employed approach for assessing mental fatigue. It entails presenting individuals with a horizontal line, typically spanning 10 cm, with anchor points situated at each end denoting extreme states of mental fatigue (e.g., "Not at all fatigued" and "Extremely fatigued"). Participants are instructed to indicate a point on the line corresponding to their prevailing level of mental fatigue. Subsequently, the distance from the "Not at all fatigued" end to the participant's mark is quantified and utilized as a measure of mental fatigue severity. Various studies have employed the VAS as a subjective gauge of mental fatigue (Matthews & Desmond, 2002; Niu et al., 2024). Participants were mandated to complete the VAS scale within a minute. If the score on the scale surpasses 50 points, it indicates that individuals have fully attained the level of mental fatigue (Niu et al., 2024).
EEG Data Acquisition
The EEG data were captured using the ANT system (eego™mylab, ANT Neuro, Netherlands). Initially, participants underwent scalp cleaning to ensure impedance levels remained below 10 kΩ. Subsequently, a high-density EEG cap outfitted with 64 electrodes was meticulously positioned on the participant's head, adhering to the international 10-20 system for electrode placement. Care was taken to adjust the cap for proper alignment and snugness, facilitating optimal electrode-scalp contact. Prior to electrode attachment, conductive gel was administered to enhance electrical conductivity. The ANT system employed a reference electrode situated on the CPz, while a ground electrode was affixed to the forehead, positioned between AFz and Fz. EEG signals underwent amplification via a high-fidelity amplifier, featuring a sampling rate of 1000 Hz and a low-pass filter set at 100 Hz. These amplified signals were subsequently digitized and stored for subsequent offline analysis.
Throughout the data collection process, participants were instructed to maintain a comfortable seated position in a quiet environment with closed eyes, minimizing exposure to external stimuli. To mitigate the risk of artifacts, participants were urged to limit body and head movements.
EEG Data Preprocessing
The EEG data underwent preprocessing using the eeglab toolbox within a Matlab script. Initially, raw data was visually inspected to detect and eliminate evident artifacts, such as EMG activities or other sources of noise. Following artifact removal, the continuous EEG data were segmented into 5s epochs, allowing for enhancement of the signal-to-noise ratio by dividing the continuous data into smaller segments. Subsequently, the data was downsampled to 250 Hz and filtered within the frequency range of 0.1 to 30 Hz, with a notch filter implemented at 50 Hz to remove powerline interference. To further refine the dataset, independent component analysis (ICA) technique was applied to mitigate artifacts associated with eye blinks, muscle activity, or other sources of interference. Finally, average re-referencing was employed to enhance the overall quality of the data, ensuring consistency and reliability throughout subsequent analyses.
EEG Power Spectrum Analysis
EEG power spectrum analysis is a widely employed technique for investigating the frequency characteristics of EEG signals and elucidating the distribution of power across various frequency bands. Initially, the Fourier Transform is applied to each epoch, transforming the time-domain EEG signal into the frequency domain. Subsequently, after the EEG data has been converted into the frequency domain, power spectral density (PSD) estimates are computed using the Welch method (Welch, P. (1967). The use of fast Fourier transform for the estimation of power spectra: A method based on time averaging over short, modified periodograms.
The PSD provides insight into the distribution of power across distinct frequency bins. In the context of this study, specific frequency bands are delineated to explore particular brainwave activities. These bands typically encompass delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) frequencies. Furthermore, the study also involves the calculation of the EEG individual alpha peak frequency (iAPF) (Zhang et al., 2021), offering additional insights into individual alpha oscillatory patterns. On the basis of relevant published research and the topography of our own data (Zhang et al., 2021), in the present study iAPF identification was at parietal-occipital regions (O1, O2, Oz, P1, P2, P3, P4, and Pz), where the average value of was calculated.
Statistical Analysis
The SPSS 19.0 and GraphPad Prism 9.0 were used to analyze the data. The Shapiro–Wilk test indicated that all the data conformed to normality distribution. Statistical analyses of behavioral data, subjective data, EEG power spectrum, and iAPF were performed using a 2×3 mixed-design ANOVA. The between-subjects variable was condition (Music and Control), and the within-subject variable was the testing phase (baseline (Pre), after mental fatigue (Post), and after music intervention (Post-20). Degrees of freedom were corrected whenever necessary using the Greenhouse-Geisser epsilon correction factor. The post-hoc multiple comparisons was conducted by Bonferroni correction to the P value. The statistical tests in gender, age, height, body mass, BMI, and education between the two groups were performed by chi-square test or independent sample t-test. The significant level was set at P <0.05.