New clues about the nature of fatigue have been found

The authors explain that the purpose of the study is to understand exactly how fatigue develops and how it can be objectively measured. According to Professor Daniel Forger, people are often let down by their own intuition: a subjective feeling of cheerfulness does not reflect well the state of the brain. The creation of reliable “fatigue signatures” can become the basis for monitoring systems that will help assess the willingness of people with a high degree of responsibility, such as pilots or surgeons, to safely perform their work.

The study required the combined efforts of scientists from the USA, Japan and Switzerland. Our foreign colleagues have developed a unique experimental approach based on light sheet microscopy, which has made it possible to create three-dimensional images of the mouse brain. A genetic tag that causes active neurons to glow has helped visualize the work of cells in different regions of the brain and at different times of the day.

The results were clear: after waking up, activity starts in the deeper subcortical structures of the brain. As the mice move through their “day,” the activity centers gradually shift to the cortex, the outer layer of the brain. The researchers compared this to the movement of urban transport: at different times of the day, not only the loads change, but also the “routes” along which the main stream of signals goes. It is important not only the level of brain activity, but also which networks take over control at a particular moment.

The authors believe that these observations will help to better understand the links between circadian rhythms, fatigue, and even mental disorders. Although the study does not directly relate to psychiatry, scientists suggest that the features of the restructuring of neural networks during the day may be important for understanding a number of diseases.

Along with biological discoveries, the computational technique developed by the research group opens up possibilities for analyzing human data. Despite the fact that the experiments use unique methods that are not applicable to humans, computer approaches can be adapted to EEG, PET, and MRI data. This allows us to hope that the principles identified in mice can be applied to the study of the human brain, including the study of fatigue, sleep and neurodegenerative diseases.