Influence of perceptual load on attentional orienting in post-stroke fatigue: a study of auditory evoked potentials

De Doncker, William; Kuppuswamy, Annapoorna · 2022 · Crossref

DOI: 10.1101/2022.03.17.484808

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Summary

This study investigates how perceptual load influences bottom-up attentional processing in individuals with post-stroke fatigue (PSF). While the impact of fatigue on top-down attention is documented, its effect on involuntary orienting responses to unexpected stimuli remains unclear. The authors hypothesized that chronic stroke survivors with high fatigue would exhibit an attenuated orienting response under increased perceptual load, reflecting compromised bottom-up selective attention. The research employed a cross-sectional observational design involving 29 first-time stroke survivors with minimal physical impairment and no clinical depression. Participants were categorized into low or high fatigue groups based on Fatigue Severity Scale scores. They performed a three-tone auditory oddball task, requiring responses to target tones while ignoring standard and novel tones. Perceptual load was manipulated by introducing background noise in half of the experimental blocks. Electroencephalography recorded auditory evoked potentials, specifically analyzing the P300a component (indicative of bottom-up orienting), P300b (top-down attention), and N100 (early sensory processing). Behavioral metrics included response time, accuracy, and subjective effort ratings. Results indicated that higher perceptual load and greater fatigue both prolonged response times, though accuracy remained unaffected across conditions. Participants reported higher effort during high-load conditions regardless of fatigue levels. Crucially, the P300a amplitude for novel stimuli was significantly attenuated in the high-fatigue group when perceptual load increased, whereas the low-fatigue group showed no such attenuation. Conversely, P300a latency increased with load only in the low-fatigue group. No significant effects of fatigue or load were observed on the P300b component, suggesting top-down attention remained intact. The N100 amplitude decreased with increased load but was not modulated by fatigue. These findings suggest that post-stroke fatigue specifically compromises bottom-up selective attention, particularly under conditions of high perceptual load. The attenuation of the P300a response in high-fatigue individuals indicates a reduced capacity to process unexpected sensory information, which may explain behavioral inflexibility and the difficulty stroke survivors face in adapting to changing environments. The preservation of P300b responses implies that this deficit is specific to involuntary orienting rather than general attentional control. This mechanistic insight supports the development of targeted therapeutic strategies to address the neural underpinnings of PSF.

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