Sound-based Meditation Alters Brain Activity: EEG Evidence for Power Reduction and Enhanced Conscious Alertness

Figure 1.. Experimental Procedure and Timeline of EEG and SSS Assessments. Notes: This figure illustrates the experimental sequence for each participant, comparing RSM and RS sessions conducted on separate days. EEG was recorded during each 26-minute session, with the Stanford Sleepiness Scale (SSS) administered before and after to assess subjective alertness.

Figure 2.. Electrode-wise Power Spectral Density Comparison Across Frequency Bands. Notes: Bar plots showing power spectral density values for each electrode across delta, theta, alpha, beta, and gamma frequency bands. Violet bars represent the RS condition, and indigo bars represent the RSM condition. The consistent pattern of reduced power during RSM (Indigo bars lower than violet bars) is evident across frontal and frontocentral electrodes in all frequency bands.

Figure 3.. Topographical Distribution of EEG Power Differences. Notes: Scalp maps display robust t-statistics (RSM minus RS) for delta, theta, alpha, beta, and gamma frequency bands. Blue regions indicate significant power reductions during RSM. Black circles mark electrodes with FDR-corrected significance (p < .05), based on Yuen’s paired t-test with 20% trimming and 2,000 permutations.

Figure 4.. Self-reported Alertness Before and After RSM and RS Conditions. Notes: Bar graph showing the percentage of participants reporting ‘Alert’ states (SSS scores 1–2) before and after each condition. Alertness decreased from 93.3% to 73.3% in the RS, while it increased from 86.7% to 93.3% after RSM, indicating enhanced subjective wakefulness following meditation.

Figure 5.. Conceptual Framework for Potential Neurophysiological Mechanisms Underlying RSM. Notes: This schematic illustrates a hypothetical model integrating our observed findings (widespread frontal EEG power reduction across all frequency bands and increased subjective alertness) with theoretical frameworks from meditation neuroscience literature. The model proposes that focused attention to AUM sound, progressing to systematic inward auditory attention, may be associated with reduced neural oscillatory activity across frequency bands (gamma, beta, alpha, theta, delta). This power suppression, particularly prominent in frontal scalp regions, potentially reflects altered spontaneous cortical processing and reduced self-referential cognition, possibly facilitating a shift toward present-moment awareness and relaxed alertness. Important limitations: This model represents a conceptual hypothesis-generating framework, not established causal pathways. Our study employed surface EEG without source localisation, precluding definitive inferences about deep brain structures (e.g., default mode network regions depicted). We did not measure connectivity between regions; arrows indicate hypothesised…