Some people survive even extreme stressful situations largely unscathed, others are thrown off course by seemingly small things. The difference lies in resilience, which is our brain’s ability to adapt and recover after a stressful event. A study now shows that about an hour after an acute stressor, adaptation processes appear in the brain that differ significantly between resilient and less resilient people. Knowledge of this sensitive time window could help to provide those affected with more targeted support in the future.
Why are some people able to deal with stressful situations better than others? What is the secret of their resilience? Do you perceive stress less intensely? Or is it just their reaction to it that differs? Most studies on the neural basis of resilience have so far taken place on animals. “But human resilience is more complex. It involves self-efficacy and past experiences – things you can’t ask a mouse,” says Noriya Watanabe of Kochi University of Technology in Japan. “To understand these higher-order mechanisms, we had to study the human brain directly as it adapts.”
Similar physical stress reactions
In order to get to the bottom of human resilience, Watanabe and his team surveyed over 100 volunteers about their resilience using a standardized questionnaire and then subjected them to a well-known stress test: The test subjects had to put their hand in an ice glove cooled to -20 degrees Celsius for two minutes. Before, during and after the intervention, the researchers observed the brain activity of their subjects using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). They also measured other physiological parameters such as pupil dilation, heart rate, breathing and the concentration of the stress hormone cortisol in saliva.
During the evaluation, the researchers first compared the physical reactions of the people who they had previously identified as more resilient based on the questionnaire with those of less resilient people. “However, we found no significant correlations between the resilience score and the physiological responses,” reports the team. Heart rate, cortisol levels and other stress indicators increased to a similar extent in the test subjects, regardless of their resilience, and fell again at a similar rate. “Our data therefore does not support the theory that more resilient people experience stress less strongly.”
Different processing in the brain
Instead, another significant difference emerged, but only with a time delay of around an hour: EEG and fMRI showed that fundamentally different processes took place in the brains of resilient and less resilient people. In less resilient people, the so-called cortical salience network, which is involved in detecting threats, was in full swing. In addition, the high-frequency beta and gamma waves, which are associated with increased attention and tension, increased in the EEG. “In contrast, activity in the cortical default mode network increased in more resilient individuals,” reports the research team. This network is associated with calm and inner reflection. At the same time, the high-frequency beta waves in the EEG decreased, an indicator of increasing relaxation.
“After an hour, the physical symptoms of stress had disappeared, but unconscious changes in the brain were still taking place,” summarizes Watanabe’s colleague Masaki Takeda. “This specific time frame explained individual differences in resilience far better than any immediate response.” Accordingly, it is how we process things afterwards that determines how well we cope with stress.
This finding could also be clinically relevant. On the one hand, the observed patterns could serve as markers, for example to estimate the risk of post-traumatic stress disorder (PTSD). On the other hand, knowledge of the sensitive time window of neuronal adaptation could also improve the acute care of patients. “Our results provide insight into an approach to recovery from stress-related problems, such as delayed neuromodulation after a stressful event,” explain the researchers.
Source: Noriya Watanabe (Kochi University of Technology, Japan) et al., Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2524075123