Ever Wondered Why Your Brain Feels Tired?
Summary: Researchers have isolated two specific brain regions that spark together when we are mentally fatigued. These discoveries, affirmed by fMRI imaging in healthy adults, may yield more accurate evaluation and treatment strategies for cognitive fatigue associated with PTSD and depression. High rewards increase mental effort despite fatigue, revealing the brain’s decision-making mechanisms
How the Brain Detects Mental Fatigue: fMRI Study Insights
Cognitive fatigue, being mentally exhausted, because you are thinking too hard, isn’t all in your head. A pioneering NIH-funded research using functional MRI (fMRI) discovered that two areas of the brain are activated at the same time when we’re mentally fatigued:
- The right insula
- The dorsal lateral prefrontal cortex
This finding can revolutionise the way we think about, assess, and treat brain fatigue in patients with depression and PTSD.
What Was the Study About?
The research, published in The Journal of Neuroscience, included 28 adults (18 women, 10 men, ages 21–29). They had fMRI scans performed while they were performing a mental task involving memory. Those tasks were specifically aimed at producing cognitive fatigue by overtaxing their working memory, such as recalling the positions of letters shown earlier in a sequence
Participants were also paid financially ($1–$8 per round), and self-reported fatigue was measured before and after each test. The more demanding the recall task, the more fatigued participants were, and increased brain activity was recorded in certain specific areas.
Which Brain Areas Are Involved?
Two major brain regions lit up consistently:
- Right Insula: Located deep within the brain, this area is closely associated with internal body feeling, specifically, fatigue.
- Dorsal Lateral Prefrontal Cortex (DLPFC): It is known to regulate working memory, attention, and executive decision-making.
Activity in these areas during mental exhaustion was greater than twice that of the baseline scans.
Why Does This Matter?
Depressed or PTSD patients typically complain of profound mental fatigue.
Dr. Vikram Chib, senior author and professor of biomedical engineering at Johns Hopkins University, says, “We now have a biological basis for understanding this cognitive exhaustion.”
This would imply that we might ultimately have objective quantitative measures of fatigue, rather than being limited to subjective self-reporting.
Motivation vs. Mental Effort: Does Money Help?
Interestingly, the participants only agreed to fight through the mental exhaustion when more financial rewards were dangled. This is consistent with previous research indicating that the brain reacts similarly when it is a question of physical effort, and lateral payoffs are what is important.
Chib suggests that the brain’s fatigue-related regions might act together to weigh whether continued mental effort is “worth it,” depending on what’s at stake.
What are the broader implications?
This research could lead the way to:
- Better diagnosis of cognitive fatigue in PTSD and depression
- Novel treatment approaches, such as targeted medication or cognitive-behavioural therapy (CBT)
- Measuring mental fatigue objectively by testing tools with fMRI
Limitations to Be Aware of
Although fMRI measures changes in blood flow, it
- Does not measure direct neuron activity
- Does not record subtle brain function
Nevertheless, it does provide very useful information about general patterns of neural activity.
Take Away: Understanding fatigue May Revolutionize Mental Health Care
This research brings us one step nearer to cracking the code of how and why our brains get tired and what this means for individuals with depression, PTSD, or long-term mental fatigue. By mapping the precise brain circuits that underpin mental effort, scientists are opening the way to tailored fatigue therapy through drugs, therapies, or behavioral treatment.
Dane
I am an MBBS graduate and a dedicated medical writer with a strong passion for deep research and psychology. I enjoy breaking down complex medical topics into engaging, easy-to-understand content, aiming to educate and inspire readers by exploring the fascinating connection between health, science, and the human mind.
