Biology subjects

McKeown, D. J.

Publications and source records attributed to McKeown, D. J..

5 recordsLinked to original sources

bioRxiv2026

Hypoxia Disrupts Multiple Processes Supporting Spatial Navigation

Hypoxia impairs cognitive function, yet its effects on navigation and intrinsic brain activity remain poorly understood. This study investigated whether a continuous exposure to hypoxia (CH) or an intermittent exposure to hypoxia (IH) differentially influence navigation performance and resting-state electroencephalography (EEG) in healthy young adults. Seventy-two participants completed sham (FiO2 = .209) and hypoxia (FiO2 = .13) sessions during either a one hour of CH or IH intervention. Navigation was assessed using the Spatial Performance Assessment for Cognitive Evaluation (SPACE), while resting-state EEG was recorded before and after the intervention in a subset of participants (n = 40). EEG spectra were parameterised into periodic (alpha and beta power and central frequency) and aperiodic (exponent and offset) components. Aligned rank transform (ART) analyses of variance examined effects of hypoxia and intervention group, while linear regression determined whether reductions in peripheral oxygen saturation (SpO2) predicted changes in navigation or EEG. Hypoxia impaired multiple components of navigation, increasing path integration distance error and egocentric pointing angle error irrespective of intervention group, while mapping accuracy was preferentially impaired following IH and perspective taking performance following CH. Hypoxia also reduced alpha and beta power, beta central frequency, and aperiodic exponent, while aperiodic offset and alpha central frequency remained stable. The reduction in aperiodic exponent was primarily evident following IH, suggesting that the temporal pattern of oxygen delivery may influence specific neurophysiological responses. Contrary to our hypothesis, SpO2 reduction did not predict individual differences in navigation performance or EEG activity. These findings demonstrate that brief, moderate hypoxic exposure can disrupt allocentric and egocentric components of spatial navigation while selectively altering periodic and aperiodic features of intrinsic brain activity.

neuroscience↗

bioRxiv2026

Long-term reliability and stability of parameterized resting state EEG: Evidence from a five-year follow-up

Several aspects of parameterized neural activity, including the aperiodic exponent and individual peak alpha frequency, have emerged as promising biomarkers for ageing, pathology, and cognitive decline. Their potential clinical application is tempered by a lack of evidence on long-term temporal stability. Existing investigations have largely relied on cross-sectional designs or considered stability for up to 90 days. Here, we examined five-year reliability, stability, and age-related changes in periodic and aperiodic neural activity using electroencephalography in adults aged 20-70 years. Resting-state EEG was recorded in two sessions, approximately five years apart. We extracted the aperiodic exponent, aperiodic offset, peak alpha power, and individual alpha peak frequency and examined test-retest reliability at both the channel and cluster levels. All parameters demonstrated fair to excellent test-retest reliability (intraclass correlations = 0.51-0.88). Linear mixed models revealed that individual peak alpha frequency decreased, the aperiodic exponent flattened, and parameterized alpha power remained unchanged. There were no interactions between time and age. Our findings suggest that parameterized activity is reliable over long timeframes, and demonstrates changes consistent with ageing-related processes. Spectral parameterization may provide a means of characterizing within-person neurophysiological changes across adulthood. Future research should explore the utility of identifying deviations that may indicate pathology.

neuroscience↗

bioRxiv2024

Lower Aperiodic Activity is Associated with Reduced Verbal Fluency Performance Across Adulthood

Age-related cognitive decline associations with human electroencephalography (EEG) have previously focused on periodic activity. However, EEG primarily consists of non-oscillatory aperiodic activity, characterised with an exponent and offset value. In a secondary analysis of a cohort of 111 healthy participants aged 17 - 71 years, we examined the associations of the aperiodic exponent and offset in resting EEG with a battery of cognitive tests consisting of the Colour-Word Interference Test, Wechsler Adult Intelligence Scale IV Digit Span Test, Rey Auditory Learning Test, Delis-Kaplan Executive Function System Trail Making Test, and the Verbal Fluency Test. Using Principal Component Analysis and K-Means Clustering, we identified clusters of electrodes that exhibited similar aperiodic exponent and offset activity during resting-state eyes-closed EEG. Robust linear models were then used to model how aperiodic activity interacted with age and their associations with performance during each cognitive test. Offset by age interactions were identified for the Verbal Fluency Test, where smaller offsets were associated with poorer performance in adults as early as 33 years of age. Greater aperiodic activity is increasingly related to better verbal fluency performance with age in adulthood.

neuroscience↗

bioRxiv2023

Test-retest reliability of spectral parameterization by 1/f characterization using SpecParam

SpecParam (formally known as FOOOF) allows for the refined measurements of electroencephalography periodic and aperiodic activity, and potentially provides a non-invasive measurement of excitation:inhibition balance. However, little is known about the psychometric properties of this technique. This is integral for understanding the usefulness of SpecParam as a tool to determine differences in measurements of cognitive function, and electroencephalography activity. We used intraclass correlation coefficients (ICC) to examine the test-retest reliability of parameterized activity across three sessions (90 minutes apart and 30 days later) in 49 healthy young adults at rest with eyes open (EO), eyes closed (EC), and during three EC cognitive tasks including subtraction (Math), music recall (Music), and episodic memory (Memory). ICCs were good for the aperiodic exponent and offset (ICCs > .70) and parameterized periodic activity (ICCs > .66 for alpha and beta power, central frequency, and bandwidth) across conditions. Across all three sessions, SpecParam performed poorly in EO (40% of participants had poor fits over non-central sites) and had poor test-retest reliability for parameterized periodic activity. SpecParam mostly provides reliable metrics of individual differences in parameterized neural activity. More work is needed to understand the suitability of EO resting data for parameterization using SpecParam.

neuroscience↗

bioRxiv2023

Medication-Invariant Resting Aperiodic and Periodic Neural Activity in Parkinson's Disease

Parkinsons Disease (PD) has been associated with greater total power in canonical frequency bands (i.e., alpha, beta) of the resting electroencephalogram (EEG). However, PD has also been associated with a reduction in the proportion of total power across all frequency bands. This discrepancy may be explained by aperiodic activity (exponent and offset) present across all frequency bands. Here, we examined differences in the eyes-open and eyes-closed resting EEG of PD participants (N = 26) on and off medication, and age-matched controls (CTL; N = 26). We extracted power from canonical frequency bands using traditional methods (total alpha and beta power) and extracted separate parameters for periodic (parameterized alpha and beta power) and aperiodic activity (exponent and offset). Cluster-based permutation tests over spatial and frequency dimensions indicated that total alpha and beta power, and aperiodic exponent and offset were greater in PD participants, independent of medication status. After removing the exponent and offset, greater alpha power in PD (vs. CTL) was only present in eyes-open recordings and no reliable differences in beta power were observed. Differences between PD and CTLs in the resting EEG are likely driven by aperiodic activity, suggestive of greater relative inhibitory neural activity and greater neuronal spiking. Our findings suggest that resting EEG activity in PD is characterized by medication-invariant differences in aperiodic activity which is independent of the increase in alpha power with EO. This highlights the importance of considering aperiodic activity contributions to the neural correlates of brain disorders.

neuroscience↗