A long day in the office can make you want to watch TV and eat a meal. You've been resting all day. Why do you feel fatigued like your friends do?

As the clock ticks down for home-time, struggling through your list of essential tasks feels even harder. It's worse when you run into a colleague on your way out.

It seems obvious that you are more likely to make decisions at the end of a long day, but people power through anyway.

A recent study that scanned people's brains at different points in their work day found high-demand tasks which require intense, constant concentration can lead to build up of a potentially toxic chemical.

Normally used to send signals from nerve cells, glutamate alters the performance of a brain region involved in planning and decision-making.

Mental fatigue has real effects. Studies show that court decisions can be affected by the judge's fatigue.

Judges are more likely to deny parole after a long day in court. According to studies, clinicians are more likely to prescribe antibiotics at the end of a tiring session.

According to a new study, cognitive functions such as focus, memory, multitasking, and problem-solving can cause fatigue of the lPFC, which can affect the decisions we make when we cross things off our list.

Opportunity cost

Circulation, breathing, motor function, and the nervous system are all regulated by the brain. Huge energy use is at the expense of the brain.

Nerve cells break down food. The process accumulates leftover molecule known as a Metabolite. There is a type of drug called glutamate. Your brain clears the toxic waste chemical in your sleep.

The authors of the Paris study wanted to know if long cognitive tasks deplete the brain's supply of vitamins. They found out if this type of high-focus demand builds up a higher concentration of toxic substances in the lPFC than other parts of the brain.

The authors compared the primary visual cortex to the l PFC.

The 40 participants were divided into two groups. Both groups sat in an office in front of a computer for a long time. One group of people had to do a lot of hard work.

The participants had to sort the letters into vowels and consonants based on the color of the letter, upper or lower. The second group did a lot of the same things as the first group. The groups had an average response rate of 80%.

The scientists scanned participants' brains and measured their levels of Metabolites. The authors read at different times of the day.

They only found fatigue markers in the high demand group. The build-up of toxic chemicals was only seen in the LFC and not the primary visual cortex.

The two groups had to make a decision after the high and low cognitive tasks. The choices about their willingness to exert physical effort, cognitive effort, and patience were included.

The rewards ranged from a low of 10 to a high of 50. After the experiment or bank transfer, there was a delay in getting the reward.

Rethinking the work day

The authors found that the high demand group preferred choices that were less taxing. The participants' pupils were less dilated and they took less time to make decisions, which indicates they experienced this part of the experiment as undemanding.

The Paris study raises questions about the format of the workday.

Taking into account the fact that performance takes a hit at the end of the day, we should break up high-demand cognitive control tasks that require working memory and constant attention. Considering the results, some professions may need to change their structure.

Air traffic controllers only guide aircraft for up to two hours during their shift. Bus drivers, clinicians, and pilots would benefit from regular, compulsory rest.

Speaking, hearing, and planning are some of the tasks that our brains are active in. The Paris study findings can't explain all of our decisions.

A study from the USA suggests that new information may be best processed in a state of hunger. It's hard to store new information when you're hungry. Fuels can be used to build circuits to store long-term memory.

A judge delivering a verdict on a case may be better in a state of satiety, while tasks that involve fine motor functions, such as surgery, may be compromised. Self interest in survival decreases after a meal because we don't have to look for food.

This will allow us to judge our environment in a more objective way. Complex fine motor skills are not at their best in this state because the body needs to rest during satiety.

When you have to make a difficult decision at the end of a long day, be aware that you will prefer low-effort actions with short-term rewards.

You should sleep on it if you can.

Professor of Developmental Neuroscience, University of Oxford and Professor of Neurobiology and Ob/Gyn, Yale University, Zoltn Molnr.

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