Biology subjects

Angus, D. J.

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

6 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↗

bioRxiv2025

Hypoxia and Cognitive Ability in Humans: A Systematic Review and Meta-Analysis

This systematic and meta-analytical review examined how a reduction in oxygen availability to tissue (hypoxia) affects cognitive function. Hypoxia had a moderate-to-large detrimental effect on general cognitive ability and across domains, including memory, attention, executive function, processing speed, and psychomotor speed. Increased hypoxic severity was associated with greater declines in general cognitive ability and executive function, while longer duration of exposure was associated with greater declines in executive function and psychomotor speed. Participant age was a moderator for executive function and psychomotor speed, with older adults experiencing greater impairments. For executive function and psychomotor speed, the magnitude of these effects was less pronounced during intermittent and hypobaric exposures, potentially due to adaptive physiological mechanisms. While our models accounted for exposure characteristics and age of participants, substantial unexplained variance remained. These findings highlight hypoxias impact on cognition and emphasize the need to investigate underlying neurophysiological mechanisms that may influence individual vulnerability.

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

Resting EEG Periodic and Aperiodic Components Predict Cognitive Decline Over 10 Years

Measures of intrinsic brain function at rest show promise as predictors of cognitive decline in humans, including EEG metrics such as individual alpha peak frequency (IAPF) and the aperiodic exponent, reflecting the strongest frequency of alpha oscillations and the relative balance of excitatory:inhibitory neural activity, respectively. Both IAPF and the aperiodic exponent decrease with age and have been associated with worse executive function and working memory. However, few studies have jointly examined their associations with cognitive function, and none have examined their association with longitudinal cognitive decline rather than cross-sectional impairment. In a preregistered secondary analysis of data from the longitudinal Midlife in the United States (MIDUS) study, we tested whether IAPF and aperiodic exponent measured at rest predict cognitive function (N = 235; age at EEG recording M = 55.10, SD = 10.71) over 10 years. The IAPF and the aperiodic exponent interacted to predict decline in overall cognitive ability, even after controlling for age, sex, education, and lag between data collection timepoints. Post-hoc tests showed that "mismatched" IAPF and aperiodic exponents (e.g., higher exponent with lower IAPF) predicted greater cognitive decline compared to "matching" IAPF and aperiodic exponents (e.g., higher exponent with higher IAPF; lower IAPF with lower aperiodic exponent). These effects were largely driven by measures of executive function. Our findings provide the first evidence that IAPF and the aperiodic exponent are joint predictors of cognitive decline from midlife into old age and thus may offer a useful clinical tool for predicting cognitive risk in aging. Significance StatementMeasures of intrinsic brain function at rest assessed noninvasively from the scalp using electroencephalography (EEG) show promise as predictors of cognitive decline in humans. Using data from 235 participants from the Midlife in the United States (MIDUS) longitudinal study, we found two resting EEG markers (individual peak alpha frequency and aperiodic exponent) interacted to predict cognitive decline over a span of 10 years. Follow-up analyses revealed that "mismatched" markers (i.e., high in one and low in the other) predicted greater cognitive decline compared to "matching" markers. Because of the low cost and ease of collecting EEG data at rest, the current research provides evidence for possible scalable clinical applications for identifying individuals at risk for accelerated cognitive decline.

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↗