Different experimental methods allegedly inducing stress were assessed in a meta-analysis. It involved 31 studies using functional magnetic resonance imaging, with stress tests applied to a total of 1279 participants, and brain activation involved in stress responses was examined. The observed regions included the following structures: Insula is, among other things, associated with pain perception, self-awareness, and social perception, and it integrates sensory and internal emotional information. It also contributes to the regulation of the response to hormonal stress. Claustrum is also responsible for integrating different kinds of information and is important for consciousness. Activation of these regions, according to the researchers, suggests that study participants direct their attention inward to their emotional processes while under stress. Dolný frontální gyrus is responsible for semantic and phonological processing and for working memory. “Activation probably occurs because many methods require demanding cognitive tasks.” Nucleus lentiformis; this nucleus is associated with movement and coordination. Its role in the context of stress is not known. “We speculate that acute stress leads to increased overall muscle tension and preparation for a possible fight-or-flight response,” explains Gesa Berretz.

The analysis also found that the methods used were to a large extent consistent in their results, and therefore appear suitable for investigating stress. Only two methods, called Cyberball and exposure to aversive material, were exceptions. In the first method, participants were socially excluded during a virtual ball game. The brain activity pattern elicited by this stress test showed less overlap with activation patterns from other methods. During aversive monitoring, participants watch disturbing film scenes with violent content, while under controlled conditions they are shown neutral film material. In some experiments involving this method, the meta-analysis found no differences between stress and control conditions. As a result, according to the researchers, special attention should be paid to the interpretation of studies that use these methods.

Author: MUDr. Radkin Honzák psychiatrist

Berretz G, et al.: The brain under stress—A systematic review and activation likelihood estimation meta-analysis of changes in BOLD signal associated with acute stress exposure. Neuroscience & Biobehavioral Reviews, 2021; 124: 89 DOI: 10.1016/j.neubiorev.2021.01.001