Stress differentially affects the sensory and decision-related processes related to the attended and unattended visual stimuli

Stress and attention are generally known to impact perceptual performance and sensory information processing. However, it is still unclear how stress may interact with the sensory and decision-making processes related to the attended and unattended stimuli. Here, we measured behavioral and EEG responses from human subjects performing a variant of Posner-cueing tasks where they discriminated the contrasts of visual stimuli that appeared at the validly and invalidly cued locations under the different levels of stress induced by changes in task difficulty across blocks of trials. Overall, we found that increasing task difficulty led to a higher stress level based on subjects’ self reports. Interestingly, stress impaired behavioral performance for both validly and invalidly cued conditions to a comparable degree. That said, at the neural level, stress produced differential effects on the event-related potentials (ERPs) evoked by the validly and invalidly cued visual stimuli. For the validly cued condition, stress reduced the amplitudes of the P1 (at ~75-100ms) and P3a components (at ~400-500ms), the well-known ERP indexes for the early sensory processing and the decision-making processes involving sensory evidence accumulation. However, there were no stress-related effects on the P1 and P3a amplitudes in the invalidly cued condition. Instead, in this condition, stress decreased the amplitude of the P2-N2 complex (at ~300-350ms) and increased the amplitude of the P3b component (at ~500-600ms; i.e., the later part of the P3 component following the P3a window), implicating slower attentional reorientation and delayed decision-making processes. Together, our results suggest that stress does not only hinder the effects that attention has on the gain amplification of early sensory responses and the speed of sensory evidence accumulation processes, but it also slows down attentional reorienting, hence impairing behavioral performance associated with both attended and unattended stimuli.