The stress hormone cortisol disrupts the brain's ability to navigate, according to a study published on March 12 in PLOS Biology by researchers from Ruhr University Bochum. The research found that individuals under the influence of cortisol performed worse in spatial orientation tasks and showed altered brain activity patterns.
Understanding how stress affects cognitive functions is important because it can impact daily life and may have implications for neurological health. The study provides new insight into how acute stress might interfere with the brain's internal GPS system.
In the experiment, 40 healthy men participated on two separate days. On one day, they received 20 milligrams of cortisol; on another, a placebo. Each time, participants completed a virtual navigation task while their brain activity was monitored using MRI scans. The test involved moving through a virtual meadow landscape toward disappearing trees and then finding their way back to the starting point without visible cues. In some trials, only temporary targets were present; in others, a lighthouse served as a permanent landmark.
Results showed that after taking cortisol, participants made more errors in finding their destinations regardless of whether landmarks were present or not. Functional MRI data revealed that grid cells—nerve cells in the entorhinal cortex responsible for spatial orientation—fired less distinctly under the influence of cortisol. This effect was especially pronounced when no landmarks were available for navigation.
"Under stress, the brain loses the ability to effectively utilize its internal navigation maps," said Dr. Osman Akan from Ruhr University Bochum's Department of Cognitive Psychology.
The study also observed increased activation in another part of the brain called the caudate nucleus when subjects had taken cortisol. Since the entorhinal cortex is among the first regions affected by Alzheimer's disease and chronic stress is considered a risk factor for dementia, these findings could help explain how stress hormones destabilize sensitive areas of the brain. "Because chronic stress is a risk factor for dementia, our study reveals a critical mechanism for how stress hormones destabilize this sensitive region," said Akan.
