NEW YORK, July 7, 2025
Brain drain decoded: Spotting fatigue’s footprint.
New research sheds light on the brain’s response to mental exhaustion.
- Brain scans reveal increased activity in two specific brain regions during cognitive fatigue.
- The study suggests a link between mental fatigue and effort-related decision-making.
- Findings could improve evaluation and treatment for fatigue in conditions like depression and PTSD.
If you’ve ever felt your brain turn to mush after a long day, you’re not alone. A new study published June 11 in the Journal of Neuroscience suggests that the feeling of cognitive fatigue is linked to activity in the right insula and the dorsal lateral prefrontal cortex.
Scientists have identified two areas of the brain that seem to work in tandem when the brain is “feeling” tired, influencing whether we push through or throw in the towel on mentally demanding tasks.
Unlocking the biology of burnout
Researchers used functional MRI (fMRI) to monitor brain activity in healthy volunteers as they performed memory tasks. The goal was to understand how the brain responds to and regulates mental effort.
“Our lab focuses on how [our minds] generate value for effort,” says Vikram Chib, Ph.D., associate professor of biomedical engineering at the Johns Hopkins University School of Medicine and a research scientist at Kennedy Krieger Institute. Chib notes that while scientists know cognitive tasks are tiring, less is understood about the biology behind this fatigue.
Memory for money
The study involved 28 participants, aged 21 to 29, who were compensated for their time and offered additional payments based on their performance. Before the tasks began, each participant received a baseline MRI scan.
During the tests, participants viewed sequences of letters and were asked to recall the position of specific letters. The difficulty increased depending on how far back in the sequence the letter appeared. Participants received feedback and were offered increasing payments ($1-$8) for more challenging exercises. They also rated their own cognitive fatigue levels before and after each test.
Brain activity spikes with fatigue
The results showed increased activity and connectivity in two brain regions when participants reported cognitive fatigue: the right insula, associated with feelings of fatigue, and the dorsal lateral prefrontal cortex, which controls working memory.
Activity in both locations more than doubled from baseline measurements, highlighting the brain’s response to mental exhaustion.
Incentives matter
Interestingly, the researchers, including Grace Steward and Vivian Looi, found that participants needed significant financial incentives to exert more cognitive effort, suggesting that external rewards can override feelings of fatigue.
“That outcome wasn’t entirely surprising, given our previous work finding the same need for incentives in spurring physical effort,” says Chib.
The bigger picture
“The two areas of the brain may be working together to decide to avoid more cognitive effort unless there are more incentives offered,” Chib explains. “However, there may be a discrepancy between perceptions in cognitive fatigue and what the human brain is actually capable of doing.”
Chib notes that fatigue is often linked to neurological conditions like PTSD and depression. He hopes that identifying these neural circuits in healthy individuals will help researchers understand how fatigue manifests in the brains of those with these conditions.
Potential treatments on the horizon
Chib suggests that medication or cognitive behavior therapy could potentially combat cognitive fatigue. He believes the current study, using decision tasks and fMRI, could serve as a framework for objectively classifying cognitive fatigue.
Future research is needed
“This study was performed in an MRI scanner and with very specific cognitive tasks. It will be important to see how these results generalize to other cognitive effort and real-world tasks,” says Chib.
**Which two brain areas are associated with cognitive fatigue?** The study results, which were funded by the National Institutes of Health (R01HD097619, R01MH119086), indicate that the right insula and the dorsal lateral prefrontal cortex are two brain areas associated with cognitive fatigue.
