الوضع الليلي
12:24:17 
2026-06-13 
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People under stress may find it harder to orient themselves in space, and researchers in Bochum have identified a possible reason why.
The stress hormone cortisol appears to interfere with the brain system that helps people navigate. It weakens the activity of grid cells, which are important for spatial orientation. Researchers at Ruhr University Bochum in Germany confirmed this effect in an imaging study involving 40 people.
Participants completed a virtual navigation task while their brain activity was monitored in an MRI scanner. Those who received cortisol before the task performed worse, and the precise activity pattern of their grid cells became harder to detect. The findings were published online in PLOS Biology.
Scientists already know that stress can affect how people think and behave. What has been less clear is how cortisol disrupts the brain circuits that support navigation. To explore this, a team led by Dr. Osman Akan from the Ruhr University Bochum Department of Cognitive Psychology worked with colleagues from the Department of Neuropsychology and researchers from University Hospital Hamburg-Eppendorf.
Virtual orientation test in the MRI scanner
The experiment included 40 healthy men, each tested on two separate days. On one day, participants received 20 milligrams of cortisol. On the other day, they received a placebo. During both sessions, they completed an orientation task while their brain activity was recorded in an MRI scanner.
In the task, participants navigated through a large virtual meadow. They moved toward a series of trees, each of which disappeared when reached. Afterward, they had to find the direct route back to the starting point without being shown the path. In one version of the task, the landscape had no permanent landmarks and included only the trees as temporary targets. In another version, a lighthouse remained visible as a fixed reference point.
Orientation worsened under the influence of cortisol
Cortisol clearly impaired the participants’ ability to orient themselves. Compared with their performance after taking the placebo, they made much larger errors when trying to reach their destinations, regardless of whether spatial landmarks were present or how complex the route was.
Neuronal coordinate system fails under stress
The effects of cortisol also appeared in the functional MRI scans. Under normal conditions, a group of nerve cells in the entorhinal cortex fires in a grid-like pattern during spatial navigation tasks. These cells, known as grid cells, act somewhat like the brain’s internal GPS.
After cortisol exposure, the grid cell activity pattern became less clear. The effect was especially strong in environments without landmarks, where the cells were almost nonfunctional. “Under stress, the brain loses the ability to effectively utilize its internal navigation maps,” explains Akan.
The researchers also observed that cortisol increased activity in another brain area, the caudate nucleus. “This indicates that the brain is trying to compensate for the loss of the main navigation system in the entorhinal cortex through alternative strategies,” says Akan.
Significance for understanding Alzheimer’s disease
The entorhinal cortex is among the first brain regions affected by Alzheimer’s disease. “Because chronic stress is a risk factor for dementia, our study reveals a critical mechanism for how stress hormones destabilize this sensitive region,” explains Akan.
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