I do a lot of work that requires intense concentration; most of it is detailed reading, writing and correcting documents. After a long day I frequently feel like my brain is broken as I simply cannot make sense of the world for a while after I stop.

I always figured it was because of the energy it took to concentrate for long periods. But as is the way of things, there’s more to it: all this concentration produces glutamate in the prefrontal cortex part of the brain, and it’s toxic (as is alcohol. Don’t go there to make it all feel better).

The research

Researchers used magnetic resonance spectroscopy (MRS) to monitor the breakdown products of the brain over the course of over six hours for two groups of people: those given mentally taxing tasks to complete and those given easier versions.

As expected, the first group started showing the signs of fatigue. However, the MRS also showed higher levels of the amino acid glutamate in the prefrontal cortex (the part associated with planning and self-regulation).

Glutamate is super important in the brain. It is important for neurotransmission (sending messages between neurons) and plays an important role in learning and memory (among other things).

However, it’s also toxic to nerve cells; it needs to be in the right place, at the right time, in the right concentration. Too much is associated with Parkinson’s, Alzheimer’s diseases. The researchers think this may be what causes the tiring effect of thinking too hard.

In other words, the reason using our brain makes us so tired may be because our prefrontal cortexes are literally getting overwhelmed with toxic byproducts of all that mental effort. The more we cogitate, the more glutamate our brains need to recycle – and the more costly each complex thought becomes.

So perhaps the answer is not to think so hard. Or sleep. I’m going with both.

Source: We Finally Know Why Thinking Too Hard Makes You Tired

I talked about this with Danny Hoyland on West Bremer Radio on 13 August 2022. Listen live each week: Saturday 7.40 am, West Bremer Radio.