The present event-related potential (ERP) study provides a unique protocol for investigating how religious chanting can modulate negative emotions. The results demonstrate that the late positive potential (LPP) is a robust neurophysiological response to negative emotional stimuli and can be effectively modulated by repetitive religious chanting.
In neuropsychological experiments, the late positive potential (LPP) is an event-related potential (ERP) component that reflects the level of one’s emotional arousal. This study investigates whether repetitive religious chanting modulates the emotional response to fear- and stress-provoking stimuli, thus leading to a less responsive LPP. Twenty-one participants with at least one year of experience in the repetitive religious chanting of “Amitabha Buddha” were recruited. A 128-channel electroencephalography (EEG) system was used to collect EEG data. The participants were instructed to view negative or neutral pictures selected from the International Affective Picture System (IAPS) under three conditions: repetitive religious chanting, repetitive nonreligious chanting, and no chanting. The results demonstrated that viewing the negative fear- and stress-provoking pictures induced larger LPPs in the participants than viewing neutral pictures under the no-chanting and nonreligious chanting conditions. However, this increased LPP largely disappeared under repetitive religious chanting conditions. The findings indicate that repetitive religious chanting may effectively alleviate the neurophysiological response to fearful or stressful situations for practitioners.
The late positive potential (LPP) has long been accompanied by emotional arousal, and it has been reliably used in emotion-related research1,2. Religious practice is widespread in both Eastern and Western countries. It is asserted that it can alleviate the practitioner's anxiety and stress when facing adverse events, especially during times of difficulty3. Nonetheless, this has seldom been demonstrated under rigorous experimental settings.
Numerous studies have confirmed that emotion regulation can be learned with different strategies and frameworks4,5,6. A few studies have shown that mindfulness and meditation can modulate the neural response to affective events7,8. Recently, it was found that meditation practitioners may employ emotion modulation strategies other than cognitive appraisal, suppression, and distraction8,9. Stimuli from the International Affective Picture System (IAPS) can be used to elicit positive or negative emotions reliably, and there are standard criteria for finding designed pictures with specified valence and arousal levels in affective research10.
Emotional stimuli can cause early- and later- responses in the brain3,11. Similarly, Buddhism tradition made analogical analysis on the mind thoughts by initial and secondary mental processes3,12,13. The Sallatha Sutta (The Arrow Sutta), an early Buddhist text, mentions that cognitive training can tame emotion. The Arrow Sutta states that both a well-trained Buddhist practitioner and an untrained person experience an initial and negative perception of pain when facing a harmful event13. This unavoidable initial pain is similar to a person being hit by an arrow, as described in the Sallatha Sutta. Early perceptual pain is identical to the stage of early processing when a person views a highly negative picture. Early neural processing usually elicits an N1 component. Untrained persons may develop excessive emotions, such as worry, anxiety, and stress, after experiencing the initial, unavoidable painful feelings. According to the Sallatha Sutta, this late-developing negative emotion or psychological pain is like being hit by a second arrow. An event-related potential (ERP) experiment may capture the current design's early and later psychological processes, assuming that N1 and LPP could correspond to the two arrows mentioned above.
In this protocol, the repetitive chanting of the name "Amitabha Buddha" (Sanskit: Amitābha) was chosen to test the potential effect of religious chanting when an individual is in a fearful or stressful situation. This religious chanting is one of the most popular practices of individuals with religious orientations among Chinese Buddhists, and it is a core practice of East Asian Pure Land Buddhism14. It was hypothesized that repetitive religious chanting would reduce the brain response to provoking stimuli, namely, the LPP induced by fearful or stressful pictures. Both EEG and electrocardiogram (ECG) data were collected to assess participants' neurophysiological responses under different conditions.
This ERP study was approved by The University of Hong Kong Institutional Review Board. Before participating in this study, all participants signed a written informed consent form.
1. Experimental design
2. Affective modulation experiment
NOTE: The experiment had two factors with a 2 x 3 design: The first factor was the picture type: neutral and negative (fear- and stress- provoking). The second factor was the chanting type: chanting "Amitabha Buddha", chanting "Santa Claus" and no chanting (silent view).
Figure 1: The experimental procedure. There were six pseudorandomized conditions, and each participant received a pseudorandomized sequence. Each condition was repeated six times in two separate sessions. This figure has been adapted from Reference3. Please click here to view a larger version of this figure.
3. EEG and ECG data collection
NOTE: Before coming to the experiment, ask each participant to wash their hair and scalp thoroughly without using a conditioner or anything else that may increase the system's impedance. Collect the EEG and ECG data simultaneously by two separate systems.
4. EEG data analysis
5. ERP source analysis
6. ECG data and behavioral assessment analysis
Behavioral results
The results for participants' belief of chanting revealed an average score of 8.16 ± 0.96 for "Amitabha Buddha", 3.26 ± 2.56 for "Santa Claus", and 1.95 ± 2.09 for the blank control condition (Supplementary Table 1).
ERP results
The representative channel of Pz (parietal lobe) demonstrated that the chanting conditions had different effects on the early (N1) and late (LPP) processing of neutral and negative pictures. It showed the time window of N1 and LPP, respectively (Figure 2).
Early perceptual stage
The ERP results showed an increased N1 while viewing the negative pictures in three chanting conditions (Figure 3). It showed that negative images induced stronger central brain activities than neutral images, and the increases are comparable in three conditions.
Late emotional/cognitive stage
The ERP demonstrated an increased LPP in the nonreligious chanting and no-chanting conditions. However, the LPP induced by negative pictures is barely visible when the participant chants Amitabha Buddha's name (Figure 4).
Region of interest (ROI) analysis
The three conditions were combined to estimate the regions that were generally activated at N1 and LPP components. Repeated measures ANOVA was performed with statistical software to calculate the difference in the N1 and LPP components between the chanting conditions (Figure 5).
The left three columns show the difference in the N1 component for the three chanting conditions: the silent viewing condition, the nonreligious chanting condition, and the religious chanting condition. The differences in the N1 component were similar across the three conditions. The right three columns show the difference in the LPP component for the three chanting conditions. This demonstrates that the difference in the LPP component is much smaller in the religious chanting condition than in the nonreligious chanting condition and the silent viewing condition.
Source analysis
Source analysis was applied to extract the potential brain mapping based on the LPP results (Figure 6). The results show that when compared with neutral pictures, negative pictures induce more parietal activation in the nonreligious chanting condition and no chanting condition. In contrast, this negative picture-induced activation largely disappears in the religious chanting condition.
Physiological results: heart rate
There was a significant change in the heart rate (HR) between the negative and neutral pictures in the nonreligious chanting condition. A similar trend was found in the no-chanting condition. However, no such HR difference was found in the religious chanting condition (Figure 7).
Figure 2: A representative channel (Pz) showed different ERPs in six chanting conditions. The six conditions are (1) religious chanting while viewing neutral pictures (AmiNeu); (2) religious chanting while viewing negative pictures (AmiNeg); (3) nonreligious chanting while viewing neutral pictures (SanNeu); (4) nonreligious chanting while viewing negative pictures (SanNeg); (5) no chanting while viewing neutral pictures (PasNeu); and (6) no chanting while viewing negative pictures (PasNeg). The channel Pz located in the mid-parietal area of the scalp. Please click here to view a larger version of this figure.
Figure 3: The ERP results for demonstrating the N1 component in the three chanting conditions. Two-dimensional maps of the N1 component for the three conditions for each picture type. In the last column, channels with significant differences (p < 0.05) are shown with dots; dots that are in darker color indicate greater significance (i.e., smaller p-values). Please click here to view a larger version of this figure.
Figure 4: The ERP results for demonstrating the LPP component in the three chanting conditions. Two-dimensional maps of the late positive potential (LPP) component for the three conditions for each picture type. In the last column, channels with significant differences (p < 0.05) are shown with dots; dots that are in darker color indicate greater significance (i.e., smaller p-values). Please click here to view a larger version of this figure.
Figure 5: Region of interest (ROI) analysis. The Region of interest (ROI) analysis on the difference between negative vs. neutral picture-induced brain responses for the early component, N1, and the late component, the late positive potential (LPP). Please click here to view a larger version of this figure.
Figure 6: Source analysis of the late positive potential (LPP) component under the three conditions. Highlighted areas indicates higher brain activity in negative vs. neutral conditions. Please click here to view a larger version of this figure.
Figure 7: The heart beat intervals under the three chanting conditions. The electrocardiogram's inter-beat intervals (RRs) under each picture type/chanting combination and the corresponding p values. Ami: Amitabha Buddha chanting condition, San: Santa Claus chanting condition, Pas: passive viewing condition, Neu: neutral picture, Neg: negative picture. Please click here to view a larger version of this figure.
Supplementary Table 1: Rating the belief in the efficacy of the chanting subject (Amitabha Buddha, Santa Claus). It uses a 1-9 scale, where 1 indicates the least belief and 9 the strongest belief. Please click here to download this Table.
Supplementary File 1: Code for EEG data batch preprocessing. It removes bad channels, resamples the data to 250 Hz, and then filters the data. Please click here to download this File.
Supplementary File 2: Code for ERP data repairing. It repairs bad epochs with noisy spikes. Please click here to download this File.
The uniqueness of this study is the application of a neuroscientific method to probe the neural mechanisms underlying a widespread religious practice, i.e., repetitive religious chanting. Given its prominent effect, this method could enable new interventions for therapists or clinicians to treat clients dealing with emotional problems and suffering from anxiety and stress. Together with previous studies, broader emotion regulation research should be considered in future studies7,8,9,22.
There are few ERP studies on chanting, given the difficulty of constructing experiments that combine chanting and other cognitive events. This study demonstrates a feasible protocol for investigating the affective effect of chanting/praying, which is rather popular in the real world. Previous functional MRI (fMRI) studies found that praying recruits areas of social cognition23. One resting-state fMRI study revealed that chanting "OM" reduced outputs from the anterior cingulate, insula, and orbitofrontal cortices24. Another EEG study found that "OM" meditation increased delta waves, inducing the experience of relaxation and deep sleep25. However, these methods could not precisely investigate the specific event-related changes after religious chanting.
Researchers should control the confounding factors of language processing and familiarity to successfully investigate the potential effect of repetitive religious chanting successfully. As the participants practiced extensively and daily chanting the name "Amitabha Buddha" (Chinese characters: ; Cantonese pronunciation: o1-nei4-to4-fat6), we used the name "Santa Claus" (Chinese characters:
; Cantonese pronunciation: sing3-daan3-lou5-jan4) as the control condition because the local is familiar with Santa Claus. In Chinese, both names contain four characters, thus controlling for language similarity. Regarding familiarity, Santa Claus is also quite popular in Hong Kong because it is a partially Westernized city. In addition, Santa Claus is also a somewhat positive figure in Hong Kong, where there is official Christmas Holidays. Nevertheless, this control of familiarity is partial, as it is difficult to entirely match the understanding of Amitabha Buddha's name for the practitioners.
One critical step in the current study was the preparation of the fear- or stress-provoking pictures. As religious chanting may work better when threatening events occur, selecting proper stimuli from the IAPS image pool26 was crucial. It is recommended that potential participants be interviewed and that suitable pictures be chosen to avoid too much fear or disgust. Highly negative pictures could prevent the participants from willfully averting their attention; at the same time, the fear- and stress- provoking stimuli should enable the participants to experience a sufficient threat. Another critical issue is the block design of the study. The EEG/ERP signal is sufficiently sensitive and dynamic to follow every event. However, it would be more appropriate to implement a block design with a 20-30 s viewing period because the pattern of cardiac function or emotion may not change on the order of seconds27. On the other hand, a 60 s block might be too long, and the neural response could become habituated in the ERP studies.
The EEG data processing stage needs to make a backup during each step, as each step alters the data and records the changes made during those steps. This can be used to track changes and make it easier to find errors during batch processing. Improving the data quality is also essential, so experience in raw data cleaning and identifying bad ICs is needed. In the statistical analysis, comparisons were made on grand averages, and ANOVA was applied. We caution that this statistic with the fixed-effect model is susceptible to random effects28. Mixed-effects models can be adapted to control extraneous factors29, and the assumption of linearity can potentially affect inferences drawn from the ERP data30.
Several limitations are worth noting. One limitation is that the current study enrolled only one group of participants who practiced Pureland Buddhism. Enrolling a control group without any experience in religious chanting for comparison could help determine whether the effect of religious chanting is mediated by belief or familiarity. Usually, a randomized controlled trial would be more convincing to examine the impact of emotion modulation on religious chanting31. However, it is difficult to guarantee that any participant would repetitively chant "Amitabha Buddha" with complete willingness. Additionally, the LPP is affected by other factors, such as emotional sound or positive priming32,33. Thus, better-controlled experiments are needed to delineate more clearly the fundamental neuro-mechanism underlying the effect of religious chanting.
In sum, previous studies have demonstrated that the human brain is subjective to neural plasticity and swift alteration of states34,35; with sufficient practice and intention, the brain can reshape itself and respond differently to normally fearful stimuli. This study provides insights into the development of effective coping strategies for handling emotional distress in contemporary contexts. Following this protocol, researchers should examine the effect of religious chanting or other traditional practices to identify feasible ways to help people ameliorate their emotional sufferings.
The authors have nothing to disclose.
The study was supported by the small fund project of HKU and NSFC.61841704.
E-Prime 2.0 | Psychology Software Tools | stimulus presentation, behavior data collection | |
EEGLAB | Swartz Center for Computational Neuroscience | EEG analysis software | |
HydroCel GSN 128 channels | Electrical Geodesics, Inc. (EGI) | EEG cap | |
LabChart | ADInstruments | physiological data (including ECG) acquisition software | |
Matlab R2011a | MathWorks | EEGLAB and SPM are based on Matlab; statistical analysis tool for EEG and physiological data | |
Netstation | Electrical Geodesics, Inc. (EGI) | EEG acquisition software | |
PowerLab 8/35 | ADInstruments | PL3508 | physiological data (including ECG) acquisition hardware |
SPM | Wellcome Trust Centre for Neuroimaging | EEG source analysis software | |
FMRIB | University of Oxford Centre for Functional MRI of the Brain (FMRIB) | Plug-in for EEGLAB to process ECG data | |
SPSS | IBM | statistical analysis tool for behavior and EEG ROI data | |
iMac 27" | Apple | running the Netstation software | |
Windows PC | HP | running the E-Prime 2.0 software | |
Windows PC | Dell | running the LabChart software |