Mathematical model shows how COVID-19 can disrupt brain function

Scientists from Immanuel Kant Baltic Federal University elaborated mathematical model, that imitates the work of neuron networks of brain of patients with COVID -19. By severe disease virus attacks astrocytes – cells, that control signal transmission between neurons. Authors showed that as a result of infection nerve cells stopped to work synchronously, that could affect cognitive abilities and memory of patients. Results of the research are published in magazine Scientific Reports.

Many functions of brain, for example, ability to memorize information and concentrate attention on something, are provided by synchronic work of nerve cells – neurons. That means that particular parts of neuronic network are activated simultaneously, and after that come into inactive state. Further this cycle repeats like waves that flow towards the shore and then move away.

Research showed that the main role in brain's activity, including such "brain waves", play astrocytes – additional cells, that surround neurons and participate in transferring signals between them.

During this process one neuron releases into the place of contact with another one a signal molecule, for example, glutamate. It in its turn can connect with receptors on astrocyte and activate molecule cascade in it, that leads to production of its own signal molecules.

Astrocyte with their help can suppress or activate transferring signals between neurons. As every astrocyte turns out to be connected with many neural endings, its activity influences whole groups of nerve cells simultaneously, thus providing the above-mentioned "brain waves".

Scientists from Immanuel Kant Baltic Federal University (Kaliningrad) together with colleagues from Lobachevsky State University (Nizhniy Novgorod) modeled work of neural network of brain of people, who suffer from COVID -19. The matter is that by severe cause of disease virus can penetrate brain and affect astrocytes. As a result, cells release less glutamate. By this the stronger the infection is the worse astrocytes release signal molecules.

Authors created artificial neural network, that models correlation of nerve cells with healthy and infected astrocytes. In the last case scientists modified mathematical formula, that describes outflow of glutamate by astrocytes so, that it could be possible to count observed decrease of level of this signal molecule.

Then researchers taught the model to activate definite groups of neurons synchronically, like they are activated during natural work of brain. It turned out that in "infected" neural network normal "brain waves" interchange with periods of asynchronous working. By this incoordinate activation correlated those phases when astrocytes didn't work out glutamate at all or released it not sufficiently. It is expected that the stronger infection was the less coordinated the work of neural network was.

Our model showed that infecting of astrocytes led to distortion of synchronic work of neurons in brain, while each separate cell continued to function normally. This observation enables to understand the fundamental causes of the fact that some people suffering from COVID-19 face decrease in memory, high anxiety and failure of attention."

Alexander Hramov, Dr. Sci. in Physics and Mathematics, professor, chief scientific officer of Baltic Centre of neurotechnologies and artificial intellect of Immanuel Kant Baltic Federal University