Capturing the multimodal dynamics of acute stress responses: Evidence from the Montreal Imaging Stress Task (MIST).

Background: Capturing multimodal acute stress responses is important for understanding how stress is expressed across psychophysiological systems. Pupil diameter and electroencephalogram (EEG) are important indices for assessing acute stress responses. However, the relationships among behavioral, pupillary, and EEG responses during sustained stress exposure remain less well understood. Methods: We collected multimodal data, including self-reported stress, salivary cortisol, electrocardiogram (ECG), pupil diameter, behavioral performance, and EEG from 33 healthy young adults during the Montreal Imaging Stress Task (MIST). Differences in responses between the training and testing conditions across difficulty levels were analyzed to characterize changes in the multimodal dynamics of acute stress responses across MIST blocks, and exploratory correlation analyses were conducted to examine associations between pupil diameter changes and relative EEG power changes. Results: The testing condition successfully elicited an acute stress response profile, reflected by increased self-reported stress, salivary cortisol, heart rate, and pupil diameter, alongside decreased behavioral performance and a shift in relative EEG power from lower to higher frequency bands. During the testing condition, behavioral performance improved and pupil diameter decreased from the medium to the hard difficulty block, accompanied by changes in relative alpha, beta (beta1, beta2, beta3), and gamma power. These findings may reflect adaptive-like changes over the course of the testing condition. Exploratory analyses showed limited associations between pupil diameter changes and relative EEG power changes, restricted to changes from the medium to the hard difficulty block in the testing condition and mainly involving frontal relative beta2 power. Conclusion: Our findings suggest that acute stress involves coordinated but partly dissociable multimodal dynamics across MIST blocks and highlight the value of integrating behavioral, pupillary, and EEG measures to characterize acute stress responses.