Scan the Pathway of Fatigue through MRI

Fatigue is commonly known as a physiologic process which is a result of lactic acid accumulation in muscles, but the origin of fatigue is seldom known. The feelings for fatigue arise in the brain as the outcome of the balance made between thought of how much and type of effort needed to overcome fatigue.

If the area of the brain where the whole mechanism of fatigue is processed is traced then it could be possible to find therapies which can reduce the fatigue.

Study was conducted by Vikram Chib, an assistant professor of biomedical engineering at the Johns Hopkins University School of Medicine and a research scientist at the Kennedy Krieger Institute to find out the processing of the brain when someone feels fatigue.

Twenty participants took part ranging from age of 18 to 34 years, 9 were female. The participants were asked to grasp and squeeze a sensor and give a score (for eg. 0 for no effort and 50 as equal to half the participant’s maximum force). Effort levels among individuals were standardized by training participants to associate units of effort with how much to squeeze.

Participants were asked to repeat the grip exercises for 17 blocks for 10 trials each, until they were fatigued followed by which they were asked to make a choice between two options first was based on a coin flip(chance to exert no effort or a predetermined effort level) and second choice was a predetermined effort level. 

Simultaneously brain activity was also scanned using functional magnetic resonance imaging (fMRI).

Results showed that 19 out of 20 participants chose a predetermined effort level when fatigued suggesting that the participants were less willing to put more effort when fatigued.

fMRI scans showed brain activity increased in all participants in insula when participants were asked to select between the two options and  the motor cortex showed decrease in activity when the participants made decisions.

Scans also showed that motor cortex decreased its activity by sending lesser signals to muscle so a balance can be maintained and over fatigue is avoided. But the participants who chose the first option and had to put more effort based on the option, showed least decrease in motor activity and got fatigued the most.

This suggests that fatigue might arise when there is an imbalance between the thoughts of an individual that he can work beyond his abilities and the actual activity in the motor cortex.

The result of this can help the researchers to find more therapies which can help people to reform their routine tasks more efficiently and better remedies can be made available for the patients of depression, multiple sclerosis and conditions where muscle fatigue is associated.