A long, hard day of thinking can sometimes feel as exhausting as a day of manual labour, and experts think they know why.
A new study has found that people may feel tired after intense mental work because it causes potentially toxic by-products to build up in the prefrontal cortex part of the brain.
This alters a person's control over decisions, so they shift toward actions that require no effort or waiting as mental fatigue kicks in.
The fatigue is a way of telling the brain to shut down in order to save itself.
Mathias Pessiglione of Pitie-Salpetriere University in France, said: "Influential theories suggested that fatigue is a sort of illusion cooked up by the brain to make us stop whatever we are doing and turn to a more gratifying activity.
"But our findings show that cognitive work results in a true functional alteration - accumulation of noxious substances - so fatigue would indeed be a signal that makes us stop working but for a different purpose: to preserve the integrity of brain functioning."
The scientists monitored brain chemistry over a working day in two groups of people - those who needed to think hard and those who had relatively easier cognitive tasks.
In the first group, they observed signs of fatigue, including reduced pupil dilation, and people in that group made choices towards options proposing reward at short delay with little effort.
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The researchers added that this group had higher levels of a chemical called glutamate in the prefrontal cortex.
They say that this supports the theory that glutamate accumulation makes further activation of this part of the brain costly, so much so that cognitive control is more difficult after a mentally tough day of work.
The findings were published in the Current Biology journal.
FAQs
Research from 2022 also revealed that thinking hard for several hours leads to the build-up of a compound called glutamate – the main molecule used by neurons for signalling – in the front of the brain.
Why is thinking hard so exhausting? ›
Concentrating for long periods builds up chemicals that disrupt brain functioning. A workday filled with a string of mentally demanding tasks can leave you feeling drained.
Why is learning new things so exhausting? ›
According to a study published Thursday in the journal Current Biology, prolonged, intense cognitive activity literally causes potentially toxic byproducts like an amino acid called glutamate to build up in our brains.
Why is mental work so exhausting? ›
Prolonged mental activity leads to the accumulation of a potentially toxic neurotransmitter in the prefrontal cortex, according to a study published in Current Biology. The researchers suggest the brain slows down its activity to manage the buildup, offering an explanation to why we feel tired.
What does cognitive fatigue feel like? ›
Cognitive fatigue is a decline in task performance that entails sustained mental activity. It may manifest in making frequent mistakes, difficulty staying focused, and taking longer to complete tasks. Management can include taking short breaks and getting a brief reprieve from stimuli, such as noise and light.
Can you be exhausted from thinking too much? ›
You probably feel tired and drained after intense physical activity, right? Well, long periods of intense mental activity can wear you out, too. To put it simply, mental exhaustion can happen when your brain receives too much stimulation or has to maintain an intense level of activity without rest.
Does thinking actually make you tired? ›
It's not just in your head: a desire to curl up on the couch after a day spent toiling at the computer could be a physiological response to mentally demanding work, according to a study that links mental fatigue to changes in brain metabolism.
How do you cure an exhausted brain? ›
Eliminating mental fatigue often involves a multi-pronged approach, including lifestyle changes like adequate sleep, regular exercise, and balanced nutrition. Mindfulness techniques such as meditation can help calm your mind, and taking short breaks to relax can also offer relief.
How do you recover from mental exhaustion? ›
How you can cope with mental and emotional exhaustion
- While it's not always possible, once you've identified the cause of your mental or emotional exhaustion, see if you can reduce or remove it. ...
- Work a break into your schedule. ...
- Avoid or limit napping. ...
- Practice gratitude. ...
- Take a walk, ideally outside.
Here are six simple ways to cope with mental fatigue and improve your mental health:
- Create a self-care plan. Focus on your well-being by devising a self-care plan tailored to your needs. ...
- Engage in regular exercise. ...
- Eat a nutritious diet. ...
- Fix your circadian rhythm. ...
- Stay organized. ...
- Strengthen your mental fitness.
For example, the following factors could potentially result in a period of poor mental health: childhood abuse, trauma, or neglect. social isolation or loneliness. experiencing discrimination and stigma, including racism.
What are the 3 types of fatigue? ›
There are three types of fatigue: transient, cumulative, and circadian: (1) Transient fatigue is acute fatigue brought on by extreme sleep restriction or extended hours awake within 1 or 2 days.
What are the symptoms of a brain shutdown? ›
Signs of a Nervous Breakdown
- Low self-esteem.
- Fearfulness.
- Irritability.
- Worrying.
- Feeling helpless.
- Getting angry easily.
- Withdrawing from family and friends.
- Losing interest in your favorite activities.
The following factors can contribute to fatigue, either alone or in combination: Psychological and psychosocial – stress, anxiety, and depression. Physical – anemia, diabetes, glandular fever, and cancer. Physiological – pregnancy, breast-feeding, inadequate sleep, and excessive exercise.
When your body shuts down from stress? ›
Our brain shuts down as a protective response to keep us safe when our nervous system is overloaded,” he says. Initially, emotionally numbing is helpful, because it helps calm our overwhelmed minds. Over time, it can be harmful and lead to behaviors with serious consequences to our emotional and physical well-being.
Do I have brain fog or am I just tired? ›
Brain fog is characterized by confusion, forgetfulness, and a lack of focus and mental clarity. This can be caused by overworking, lack of sleep, stress, and spending too much time on the computer.
Why is thinking so difficult for me? ›
A common symptom of depression is 'fuzzy thinking', the inability to think clearly. It can feel as if your brain is set on low, or your head is filled with wet sand. Focus becomes very difficult. Anxiety, on the other hand, tends to leave your mind racing on repeat.
Why does my brain get tired when I think? ›
Performing complex cognitive tasks leads to glutamate accumulating in a key region of the brain, a study finds, which could explain why mental labor is so exhausting.
