Event-induced modulation of aperiodic background EEG: Attention-dependent and age-related shifts in E:I balance, and their consequences for behavior

Kałamała, Patrycja; Gyurkovics, Máté; Bowie, Daniel C.; Clements, Grace M.; Low, Kathy A.; Dolcos, Florin; Fabiani, Monica; Gratton, Gabriele · 2023 · Imaging Neuroscience

DOI: 10.1162/imag_a_00054

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Summary

This study investigates the dynamic temporal changes in the aperiodic component of electroencephalography (EEG) signals, specifically the spectral slope, which serves as an index of the balance between cortical excitation and inhibition (E:I balance). While previous research established that older adults exhibit a flatter spectral slope indicative of increased neural noise and reduced inhibition, no studies had examined how this activity fluctuates during specific phases of information processing or how these dynamics relate to behavior. The authors aimed to characterize event-induced modulations of the spectral slope in younger and older adults and determine their impact on cognitive performance. The researchers re-analyzed scalp EEG data from 43 participants (21 younger adults, mean age 21.5; 22 older adults, mean age 71.2) performing a cued flanker task. Participants viewed pictorial cues that varied in task relevance, novelty, and valence, followed by an imperative stimulus requiring a speeded response. EEG data were segmented into four 500-ms time windows relative to cue onset: a pre-cue baseline and three post-cue windows capturing early, middle, and late processing phases. To isolate the aperiodic component from phase-locked event-related potentials (ERPs), the authors subtracted ERP spectra from total power spectra before parametrizing the remaining signal using the `specparam` algorithm. This allowed for the calculation of spectral slope shifts (changes in steepness) independent of standard ERP effects. The results revealed a biphasic modulation of the spectral slope following cue presentation. Initially, the slope steepened (indicating increased inhibition) similarly in both age groups. This was followed by a flattening of the slope (indicating increased excitation), which was significantly more pronounced in older adults. These dynamic shifts were independent of concurrent ERPs. Crucially, the magnitude of the slope flattening was negatively correlated with behavioral performance; greater flattening predicted slower reaction times and larger congruency costs. Furthermore, novel cues mitigated the shift toward excitation in older adults, partially restoring their E:I balance and reducing congruency costs compared to repetitive cues. These findings demonstrate that the broadband shape of the EEG spectrum varies dynamically during information processing and that these variations are predictive of subsequent behavior. The study provides evidence that age-related cognitive decline is linked to a failure to maintain inhibitory control during specific processing phases, resulting in excessive excitation. By showing that novel stimuli can help restore E:I balance in older adults, the research highlights the functional relevance of aperiodic EEG activity and offers new insights into the neural mechanisms underlying aging and cognitive control.

Key finding

Older adults exhibit a greater event-induced shift toward cortical excitation in the aperiodic EEG spectrum compared to younger adults, which correlates with poorer cognitive performance, though novel cues can mitigate this effect.

Methodology

lab_experiment

Sample size: 43

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• cognitive aging