Same Performance, Different Neural Cost: Effects of Chronic Stress on Brain Oscillations During Selective Attention

Chronic stress is a maladaptive response to persistent noxious stimuli that induces neurobiological alterations affecting cognitive processes. Behavioural performance often remains stable in such states, yet the neurophysiological mechanisms of selective attention require more precise characterisation. This study assessed the impact of perceived chronic stress on brain oscillations by analysing spectral density during an auditory selective attention task. Participants were classified into Low Perceived Stress (LPS) and High Perceived Stress (HPS) groups using the Perceived Stress Scale (PSS-14). Brain electrical activity was recorded with a 32-channel EEG system during a digits-in-noise (DiN) test, and signals were processed with MNE-Python. Time-frequency analysis used a complex Morlet wavelet (2–45 Hz) to estimate spectral power across groups. Behavioural performance showed no significant differences: both groups achieved a comparable number of correct responses. Electrophysiological analysis, however, revealed significantly higher spectral density in Beta and Gamma oscillations in the HPS group during correct trials, in both frontal and parietal regions. Individuals with high chronic stress therefore sustain performance equivalent to non-stressed individuals at a higher neural cost, since compensatory recruitment of high-frequency activity indicates that additional neural resources are needed to execute selective attention tasks.