Researchers are studying stress tests that trigger similar brain activation patterns

Scientists use many different tests to study what goes on in the brains of people under stress. It is not known to what extent the different methods with which subjects are stressed are comparable to each other. In a meta-analysis, a biopsychology team from the Ruhr-Universität Bochum compared 31 previous studies that had investigated stress using functional magnetic resonance imaging (fMRI).

The team determined which regions of the brain are activated as standard during stress and which stress tests trigger similar activation patterns. They describe the results in the journal Neuroscientific and biobehavioural journals, published online 5 February 2021.

To conduct the work, Gesa Berretz, Dr Julian Packheiser and Professor Sebastian Ocklenburg from the Department of Biopsychology collaborated with Professor Robert Kumsta, genetic psychology, and Professor Oliver Wolf, cognitive psychology.

Activation models from 31 studies compared

“We know that stress influences the whole process of information processing, for example attention, working memory and long-term memory,” explains Gesa Berretz. “But so far there has been no consensus on how these different situations induce the same feeling of stress and what is going on in the brain.”

Many researchers are trying to clarify this question and use different methods to induce stress in their study participants. In doing so, they measure the subjects’ brain activity using fMRI. Activation patterns are shown as coordinates in three-dimensional space, representing regions of the brain that were active during the stress test.

The Bochum-based team evaluated 31 studies using what’s called an activation probability estimate analysis. During this time, the researchers compared the coordinates of the activation patterns of all the studies and statistically checked how similar the patterns were. Data from 1279 subjects were included. The result: A range of areas of the brain, including the insula, claustrum, lentiform nucleus, and inferior frontal gyrus, were always activated, regardless of the stress test applied. “These areas of the brain seem to play a central role in stress”, summarizes Gesa Berretz.

The potential role of brain regions in stress

The insula is, among other things, associated with pain perception, self-awareness and social perception, and integrates internal sensory and emotional information. It is also involved in controlling the hormonal stress response. The claustrum is also responsible for integrating various information and is important for consciousness. Activation of these regions indicates, according to the researchers, that study participants direct their attention inwardly towards their emotional processes when under stress.

The inferior frontal gyrus is responsible for semantic and phonological processing and working memory. “Activation probably occurs because many methods involve demanding cognitive tasks,” the authors assume.

The lentiform nucleus is associated with movement and coordination. Its role in the context of stress is not known. “We believe that acute stress leads to an increase in overall muscle tension and preparation for a possible fight-or-flight response,” explains Gesa Berretz.

Two stress tests appear as outliers

The analysis also revealed that the methods used have largely yielded consistent results and therefore appear to be well suited to the study of stress. Only two methods, called Cyberball and Aversive Visualization, were exceptions. In the first method, subjects were socially excluded during a virtual ball game. The brain activity pattern triggered by this stress test showed less overlap with activation patterns of other methods.

During aversive viewing, subjects watch disturbing film scenes with violent content, as they are shown neutral film material under controlled conditions. In some experiments involving this method, meta-analysis found no difference between stress and control conditions. As a result, according to the researchers, special attention should be paid to the interpretation of studies using these methods.