It Really Is in Your Head: Thinking Hard and Long Can Cause Brain Drain

Wallace D. Wattles claimed that thinking is the hardest and most exhausting of all labor.

A new study suggests that thinking too hard and too long can drain your brain, just like exercising can wear out the body.

The sweat on a person's brow or the quivering of their muscles doesn't show how hard they're thinking.

We just have to take the person's word for it.

Scientists don't understand why cognitive fatigue occurs. It's not a feeling of being sleepy, it's a feeling that tasks are getting harder to complete.

Researchers think the most abundant excitatory neurotransmitter in the brain is to blame for the lack of mental endurance.

Despite the fact that it is present in over 90 percent of the human brain, glutamate was only described in the 1950's.

Scientists have been surprised by this underestimated chemical over the years. The strength of signals in the brain can be controlled by the amount of glutamate that is released to other neurons.

There are as many as 8,000 glutamate molecules encapsulated in a single pouch of a synapse.

It has been shown that brain drain is caused by the over abundance of glutamate.

When monitoring the brain chemistry of 24 participants tasked with completing strenuous computer-based sorting tasks for over 6 hours, researchers found an increase in glutamate in the prefrontal cortex. The part of the brain associated with higher-order cognitive powers is called the cortex.

16 other participants who were assigned easier tasks for the day did not show signs of brain damage.

One of the limiting factors to human mental endurance might be a rise in extracellular glutamate.

The brain eats a lot of sugar when it's working. It's not clear how a loss of glucose makes thinking harder, but other theories suggest it is.

A loss of dopamine in the brain can cause people to lose interest in certain cognitive tasks.

According to a clinical psychologist from the Pitié-Salptrire University in Paris, France, fatigue is a sort of illusion cooked up by the brain to make us stop whatever we are doing.

"Our findings show that fatigue is a signal that makes us stop working, but for a different reason: to preserve the integrity of brain functioning."

According to Pessiglione, there is good evidence that glutamate is eliminated from the brain during sleep.

A night of rest can help a person feel refreshed the next day.

A brain study done in 2016 found that the lPFC was involved in cognitive effort that diminished its excitability over time.

It would take more effort to get this region activated at the end of the day. The feeling of brain draining.

Pessiglione and colleagues conclude that the results support a neuroscience model that shows that cognitive control is harder to mobilize after a long workday.

There is a neurotransmitter called glutamate. It's part of the reason why this acid is so powerful. It makes it hard to measure.

New technology is being used to explore the role of glutamate in our brains in a more detailed way.

The authors want to find out why the prefrontal cortex has more of the substance in it than other parts of the brain.

The study was published in a scientific journal.