Emotional stress regulation: The role of relative frontal alpha asymmetry in shaping the stress response.

Frontal EEG asymmetry has been proposed as an index of emotional regulation, reflecting both state and trait components, and there is evidence that these factors influence the cortisol response to stress. Here, we asked whether cold pressor stress modulates frontal asymmetry and whether this is predictive of the neuroendocrine stress response. Twenty-four male participants underwent an automatized bilateral feet cold pressor test (bfCPT) and a warm water control procedure in counterbalanced order on two separate days, one week apart. EEG, heart rate and blood pressure were assessed at baseline as well as during and after the bfCPT. Salivary cortisol and subjective ratings of stress and arousal were assessed before and after the bfCPT. The bfCPT led to a significant increase in cortisol, cardiovascular parameters and in subjective ratings of stress and arousal that was absent in the control condition. Furthermore, analysis of relative frontal alpha-band asymmetry revealed a stronger relative right frontal activation during the bfCPT compared to the control condition at electrode pairs F7/8 but not F3/4. However, frontal asymmetry scores during the bfCPT were not predictive for neither physiological responses nor subjective ratings. Moreover, an association between physiological responses and frontal asymmetry assessed during rest at baseline could be observed at electrode pairs F3/F4, with stronger responses being associated with stronger relative right frontal activation. Our results show that cold pressor stress leads to an alteration of emotional processes as reflected in frontal EEG asymmetry at F7/F8. Moreover, physiological responses to the CPT seem to be differentially moderated by trait and state components present in frontal asymmetry.