Discovering neural pathways that lead to tiredness

10 September 2020 | Muriel Cozier

Improved understanding of how the brain regulates fatigue could lead to new therapies.

Researchers from Johns Hopkins Medicine, Maryland, US, believe that they have pinpointed areas of the human brain that control fatigue.

Using MRI scans and computer modelling, the researchers say that their findings could lead to better understanding of the neural mechanisms that contribute to fatigue in people with depression and multiple sclerosis. The work has been published in Nature Communications.

Vikram Chib, PhD, assistant professor of biomedical engineering at the Johns Hopkins University School of Medicine and research assistant at the Kennedy Krieger Institute, explained that while the physiological processes involved in fatigue, such as build up of lactic acid in muscles were understood, much less is known about how feelings of fatigue are processed in brain.

Knowing the brain regions that control choices about fatigue-moderating efforts, can help scientists find therapies that precisely alter those choices. ‘It might not be ideal for your brain to simply power through fatigue,’ said Chib. ‘It might be more beneficial for the brain to be more efficient about the signals it is sending.’

Having developed a novel way to quantify how people ‘feel’ fatigue, the research team used fMRI scans to take a closer look at the motor cortex of the brain when participants were fatigued. This is the region of the brain responsible for exerting effort. The team found that in line with other studies, performing repeated fatiguing exertions led to a decrease in motor cortex activity, associated with fewer signals being sent to the muscles. The researchers believe that the body attunes to the motor cortex when it becomes fatigued. If the brain kept sending signals to muscles to act, physiological constraints would begin to take over, for example increased lactic acid, contributing to more fatigue.

As well as helping those with debilitating fatigue conditions, Chib believes that the research could lead to therapies that can improve performance in healthy people.

DOI: 10.1038/s41467-020-17855-5 9/8/2020

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