A first fatigue born in the execution of a task but can disappear after a short rest but, over time, a second fatigue appears and prevents the continuation of the tasks in progress, even if there is a reward at stake .
- The two different types of fatigue were spotted in separate parts of the brain.
- The ventral striatum indicates how much fatigue influences people’s motivation to keep working.
Fatigue, that is, the feeling of exhaustion due to performing demanding tasks, is something we all experience on a daily basis. It makes us lose motivation and makes us want to take a break. The influence of fatigue on the mechanisms the brain uses to decide whether a given task is worth doing is not well understood. In a study published on July 28 in the journal NatureCommunicationsBritish researchers from the University of Oxford have tried to better understand this process.
Two noticeable fatigues in different parts of the brain
The researchers found that there are two different types of fatigue which they detected in separate parts of the brain. In the first case, fatigue is experienced as a short-term sensation, which can be overcome after a short rest. Over time, however, a second, longer-term feeling builds up that keeps people from wanting to work. This fatigue does not go away with short rests. “We found that people’s willingness to exert effort fluctuated from moment to moment, but gradually decreased as they repeated a task over time.explains Tanja Müller, first author of the study, based at the University of Oxford. Such changes in work motivation seem to be related to fatigue and sometimes make us decide not to persist..”
The team tested 36 healthy young people on a computer task. They were asked to exert physical effort to obtain different amounts of monetary rewards. Participants completed over 200 trials and in each they were asked whether they would rather work out – which involved squeezing a grip strength device – and get the highest rewards, or rest and earn only a small reward. The team built a mathematical model to measure fatigue, and how much it influences the decision to work or rest. While performing the task, participants also underwent MRI scans, which allowed the researchers to look for activity in the brain that matched the model’s predictions.
The frontal cortex and the ventral striatum
The results revealed that areas of the brain’s frontal cortex have activity that fluctuates in line with the math tool’s predictions, while an area called the ventral striatum indicates how much fatigue influences people’s motivation to keep working. “This work offers new ways to study and understand fatigue, its effects on the brain, and why it may change motivation for some people more than others.says Dr. Matthew Apps, lead author of the study. It helps to begin to understand something that affects the lives of many patients, as well as people at work, school, and even elite athletes..”
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