Chan, R. H. M. | Search bioRxiv

bioRxiv2025

Lifespan Trajectories of Alpha Rhythm: Dynamic Shifts in Neural Excitation-Inhibition Balance

Alpha rhythm (8-13 Hz), a key neural oscillation in the brain, plays a significant role in cognitive functions and reflects the brains excitatory-inhibitory (E-I) balance. This study investigates the dynamics of alpha rhythm across the lifespan, focusing on how E-I balance modulates alpha power and peak frequency, and exploring the distinct age-related and sex-specific patterns of alpha activity. Using a computational E-I model, we simulated the impact of different neuronal connections and E-I ratios on alpha rhythm characteristics. The results suggest that self-regulation primarily affects alpha power, while interaction between excitatory and inhibitory neurons influences both alpha frequency and power. We applied this model to real EEG data from 3265 participants across a wide age range, revealing that alpha power and peak frequency exhibit an inverted U-shape across the lifespan, peaking in early adulthood and declining in old age. Significant sex differences in alpha activity were observed primarily during puberty and later in life. Decomposition of the alpha band into periodic and aperiodic components showed that periodic activity follows the inverted U-shape, while aperiodic activity declines exponentially with age. Our findings indicate that alpha rhythm is governed by complex E-I dynamics, with distinct contributions from periodic and non-periodic components, and highlight the role of alpha rhythm in age-related cognitive changes and sex differences in brain function.

neuroscience↗

bioRxiv2024

Aging amplifies sex differences in low alpha and low beta EEG oscillations

Biological sex profoundly shapes brain function, yet its precise influence on neural oscillations was poorly understood. Despite decades of research, studies investigating sex-based variations in electroencephalographic (EEG) signals have yielded inconsistent findings that obstructs what may be a potentially crucial source of inter-individual variability in brain function. To address this, we analyzed five publicly available resting-state datasets, comprising EEG data (n=445) and iEEG data (n=103). Our results revealed striking age-dependent sex differences: older adults (30-80 years) exhibited robust sex differences, with males showing heightened low alpha (8-9 Hz) activity in temporal regions and attenuated low beta (16-20 Hz) oscillations in parietal-occipital areas compared to females. Intriguingly, these sex-specific patterns were absent in younger adults (20-30 years), suggesting a complex interplay between sex and aging in shaping brain dynamics. Furthermore, we identified consistent sex-related activity in the precentral gyrus with the results of scalp EEG, potentially driving the observed scalp EEG differences. This multi-level analysis allowed us to bridge the gap between cortical and scalp- level observations, providing a more comprehensive picture of sex-related neural dynamics. To further investigate the functional implications of these oscillatory differences, we conducted correlation analyses to uncover significant associations between sex-specific oscillatory patterns and several lifestyle factors (behavioral and anthropometric measures) in older adults. This comprehensive investigation demonstrates the complex interplay between sex, age, and neural oscillations, revealing the variability in brain dynamics. And our findings highlight the importance of careful demographic consideration in EEG research design to ensure fairness in capturing the full spectrum of neurophysiological diversity. Significance statementThe influence of biological sex and age on neural oscillations had been a long- standing, unresolved question in EEG research, largely unaddressed due to limited sample sizes and simplistic demographic matching. Our study leverages large-scale, open datasets to tackle this issue, analyzing hundreds of participants across five datasets. Our findings demonstrate substantial sex- based differences in even resting-state EEG baselines, particularly in low alpha and low beta bands, uncovering a significant source of variability in neural activity. By connecting these sex and age-related variations to potential neural circuit mechanisms and lifestyle factors, our findings highlight the importance of careful demographic consideration in EEG research design in EEG experimental design to accurately capture the rich spectrum of neurophysiological variability across the lifespan.

neuroscience↗