Shifts in broadband power and alpha peak frequency observed during long-term isolation

Abstract

Prolonged periods of social isolation and spatial confinement do not only represent an issue that needs to be faced by a few astronauts during space missions, but can affect all of us as recently shown during pandemic situations. The fundamental question, how the brain adapts to periods of sensory deprivation and re-adapts to normality, has only received little attention. Here, we use eyes closed and eyes open resting-state electroencephalographic (EEG) recordings to investigate how neural activity is altered during 120 days of isolation in a spatially confined, space-analogue environment. After disentangling oscillatory patterns from 1/f activity, we show that isolation leads to a reduction in broadband power and a flattening of the 1/f spectral slope. Beyond that, we observed a reduction in alpha peak frequency during isolation, but did not find strong evidence for isolation-induced changes that are of oscillatory nature. Critically, all effects reversed upon release from isolation. These findings suggest that isolation and concomitant sensory deprivation lead to an enhanced cortical deactivation which might be explained by a reduction in the mean neuronal population firing rate.

Resting-state aperiodic neural dynamics predict individual differences in visuomotor performance and learning

“…The aim of the present work was to assess if 1/ƒ aperiodic neural dynamics predict visuomotor performance. Aperiodic resting-state EEG activity is thought to be behaviourally relevant in predicting cognitive capacity (Cross et al, 2020;Ouyang et al, 2020) with higher 1/ƒ intercept reflecting higher neural population spiking (Manning et al, 2009;Miller et al, 2012) and steeper 1/ƒ slope reflecting a greater excitation-inhibition balance (Lendner et al, 2020;Weber et al, 2020). Despite the apparent association between 1/ƒ aperiodic parameters and information processing capacity, to date, there has been no empirical test of these parameters as individual predictors of visuomotor performance.…”

“…The power-law exponent, or β, reflects the steepness of the 1/ƒ slope, with higher β values indicating a steeper slope and lower values reflecting a shallower (i.e., flatter) slope (He, 2014). Mechanistically, the 1/ƒ slope is argued to reflect an excitation-inhibition balance in recurrent neural networks which maximises information processing capacities (Lendner et al, 2020;Weber et al, 2020), with steeper slopes indexing enhanced neural inhibition and vice versa. Aperiodic activity can also be quantified by its spectral offset (i.e., the intercept), with a higher intercept hypothesized to be reflective of increased neural population spiking (Manning et al, 2009;Miller et al, 2012), and is positively correlated with the blood-oxygen-level-dependent (BOLD) signal (Winawer et al, 2013;Jacob et al, 2021) obtained from functional magnetic resonance imaging (fMRI).…”

“…Given that the 1/ƒ intercept reflects mean neural population spiking and, by extension, higher broadband power (Donoghue et al, 2020), a higher resting-state intercept would be expected to predict both motor and perceptual performance. Further, as a steeper 1/ƒ slope indexes greater neural excitation-inhibition balance to the extent of maximising information processing (Lendner et al, 2020;Weber et al, 2020), then a steeper resting-state slope would predict greater capacity for visuomotor processing speed and perceptual sensitivity to target information. We also investigated if individual 1/ƒ intercept and slope predicted performance over increased task difficulty by including four task blocks were target selection was rendered more complex by the presence of multiple targets as well as non-targets.…”

One-week escitalopram intake shifts excitation-inhibition balance in the healthy female brain

“…A recent interventional rs-EEG study in healthy humans showed that ketamine and anesthesia administration, which respectively tip the balance in favor of cortical excitation (increase in EIB) and inhibition (decrease in EIB), resulted in the expected decrease and increase in 1/f slope (33). Since then, several recent studies have shown the reliability of this measure using human scalp EEG activity in both healthy (29)(30)(31) and clinical populations (6,29,34).…”

“…Neurophysiological brain signal consists of periodic oscillatory activity and aperiodic activity (1/f slope) of the non-oscillatory PSD background (27), which have been shown to play functionally distinct roles (28). While more conventional approaches have focused on narrowband oscillations or frequency band ratios, there has been a current upsurge in neuroscience research in the past year focusing on 1/f slope as a unique neurophysiological marker (6,(28)(29)(30)(31). Simulation data with local field potentials demonstrate that 1/f slope inversely reflects EIB (32), a finding that has been validated in in vivo animal models in which anesthesia administration led to an increase in 1/f slope or steepening of the PSD decay (32).…”