ORIGINAL RESEARCH article
Front. Cognit.
Sec. Neural Networks and Cognition
This article is part of the Research TopicModulation of Neurostimulation Effects by Fluctuations of Ongoing Activity in the (Central) Nervous SystemView all articles
Cognitive-load dependent effects of HD-tDCS on the executive vigilance decrement: insights from aperiodic EEG activity
Provisionally accepted
- 1Department of Psychology and Cognitive Science, University of Trento, Rovereto, Italy
- 2Universidad de Granada Departamento de Psicologia Experimental, Granada, Spain
- 3Universidad de Granada Centro de Investigacion Mente Cerebro y Comportamiento, Granada, Spain
- 4University of Surrey School of Psychology, Guildford, United Kingdom
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This study investigated cognitive-load-dependent effects of high-definition transcranial direct current stimulation (HD-tDCS) on the executive vigilance (EV) decrement and its modulation by aperiodic electroencephalography (EEG) markers. Given the relevance of vigilance for daily functioning and its susceptibility to decline over time, we examined whether HD-tDCS could counteract this decrement under varying cognitive demands. In a between-participant design (N = 180), anodal HD-tDCS was applied over the right posterior parietal cortex (rPPC) during single-, dual-, or triple-task performance, with on-task EEG recorded pre- and post-stimulation. Power spectra were parametrized to extract aperiodic (non-oscillatory) components; the aperiodic exponent and offset across two frequency ranges (1–35 and 30–45 Hz). HD-tDCS induced a reduction in the aperiodic exponent within the 30–45 Hz range (i.e., flattening of the spectral slope), consistent with increased cortical excitation. This change was associated with a mitigated EV decrement under high task demand and an exacerbated decrement under low demand, suggesting a mechanistic link between changes in excitation/inhibition balance and behavioural outcomes. However, these effects reached significance only under a directional hypothesis and seemed to be obscured by a push-pull relationship with the aperiodic offset, indicating a more complex interaction between local excitability and broadband spectral dynamics. Baseline aperiodic markers did not significantly moderate the stimulation effect but predicted overall task performance, independent of stimulation. These findings suggest a mechanistic understanding of how endogenous neural activity, specifically, aperiodic EEG features, modulates brain stimulation outcomes. By demonstrating that HD-tDCS effects vary as a function of cognitive load and spectral dynamics, the study underscores the need for future research, centered on refined, state-sensitive stimulation protocols to mitigate the EV decrement.
Keywords: Aperiodic exponent, aperiodic offset, EEG, Executive vigilance, HD-tDCS, spectral parametrization, vigilance
Received: 31 Jul 2025; Accepted: 19 Dec 2025.
Copyright: © 2025 Hemmerich, Lupiáñez, Martín-Arévalo and Cohen Kadosh. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Klara Hemmerich
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