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1- Department of Physiology, Edo University Iyamho, Ogbida, Nigeria.
2- Department of Physiology, Enugu Campus, University of Nigeria, Nigeria.
3- Department of Physiology, University of Delta, Nigeria.
2- Department of Physiology, Enugu Campus, University of Nigeria, Nigeria.
3- Department of Physiology, University of Delta, Nigeria.
Abstract:
Background: Low-frequency acoustic stimulation can entrain brain oscillations, yet most studies have emphasized gamma-range auditory inputs. The region-specific cortical effects of sub-gamma low-frequency pitch tones in healthy adults remain largely unexplored, and safety concerns persist due to historical reports of adverse effects at high intensities.
Objective: To characterize safe, sub-threshold, low-frequency pitch–induced modulation of cortical oscillations and connectivity using EEG in healthy adults.
Methods: Twenty adults were exposed to pure tones (30, 45, and 60 Hz) at intensities <40 dB SPL; well below thresholds associated with adverse neurological effects, under controlled laboratory conditions. EEG was recorded from 8 strategically placed electrodes (covering frontal, parietal, occipital, and temporal regions) using the international 10–20 system, enabling targeted region-of-interest (ROI) analysis while minimizing noise and redundancy. Power spectral density and alpha-band phase-locking values (PLVs) quantified spectral and connectivity changes.
Results: Safe-level low-frequency stimulation elicited region-specific increases in alpha and theta power in frontal, parietal, and occipital cortices (p < 0.05), particularly at 30–45 Hz. Alpha-band PLVs showed enhanced frontal–parietal, frontal–occipital, and parietal–occipital coupling (p < 0.05). Pitch and exposure duration significantly predicted oscillatory changes (p = 0.0018).
Conclusion: Contrary to prior studies linking low-frequency sound to risk at high intensities, our findings demonstrate safe, targeted neuromodulation at sub-threshold levels, revealing frequency-specific entrainment patterns with potential cognitive and therapeutic applications.
Objective: To characterize safe, sub-threshold, low-frequency pitch–induced modulation of cortical oscillations and connectivity using EEG in healthy adults.
Methods: Twenty adults were exposed to pure tones (30, 45, and 60 Hz) at intensities <40 dB SPL; well below thresholds associated with adverse neurological effects, under controlled laboratory conditions. EEG was recorded from 8 strategically placed electrodes (covering frontal, parietal, occipital, and temporal regions) using the international 10–20 system, enabling targeted region-of-interest (ROI) analysis while minimizing noise and redundancy. Power spectral density and alpha-band phase-locking values (PLVs) quantified spectral and connectivity changes.
Results: Safe-level low-frequency stimulation elicited region-specific increases in alpha and theta power in frontal, parietal, and occipital cortices (p < 0.05), particularly at 30–45 Hz. Alpha-band PLVs showed enhanced frontal–parietal, frontal–occipital, and parietal–occipital coupling (p < 0.05). Pitch and exposure duration significantly predicted oscillatory changes (p = 0.0018).
Conclusion: Contrary to prior studies linking low-frequency sound to risk at high intensities, our findings demonstrate safe, targeted neuromodulation at sub-threshold levels, revealing frequency-specific entrainment patterns with potential cognitive and therapeutic applications.
Keywords: Low-frequency pitch stimulation, EEG spectral analysis, Cortical oscillations, Alpha-band connectivity, Functional connectivity, Auditory neuromodulation
Type of Study: Original |
Subject:
Cognitive Neuroscience
Received: 2025/08/23 | Accepted: 2026/01/5
Received: 2025/08/23 | Accepted: 2026/01/5
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