Connectomics: Networks in the brain

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Connectomics: Networks in the brain
Connectomics: Networks in the brain

The Network of the Mind

Our mental activity arises from the carefully coordinated interaction of different brain areas. Any disruption can have fatal consequences.

Networks determine our lives. Every day we use a complex network of roads, rails, shipping lanes and flight routes. There are also others that elude our immediate perception, such as the World Wide Web, the power grid and last but not least the universe, in which the Milky Way represents a tiny node in a seemingly endless network of galaxies. But few of them reach the complexity of the neural networks in our heads.

Brain researchers like to demonstrate the activity of brain areas using colored illustrations. In it, they mark the regions that "light up" in the brain scanner during a mental task, such as the occipital lobe when we look or the temporal lobe when we remember something. However, what does not emerge from these representations is the fact that the areas are highly interconnected and actively exchange information with one another. Because the actual basis of our thinking is a network of almost 100 billion neurons with at least 100 trillion connection points, the synapses.

To study and predict the complex neural interactions, our group and other research teams use mathematical methods. One of them is graph theory. We do the following: We model graphs with so-called nodes and edges from the data from brain imaging processes. The former represent the units of the network, for example the neurons. We can visualize them as airports. The edges, on the other hand, symbolize the connections between them, i.e. the nerve cell extensions that interconnect brain regions as tracts of the white matter. In our picture they correspond to the flight routes of air traffic. Our current models reduce the human brain to a graph with about 300 nodes.

The functioning of the networks can best be compared to a symphony orchestra. Until now, neuroscientists have largely analyzed the functioning of individual brain regions in isolation. They basically heard strings, brass, woodwinds et cetera individually. It is also interesting to learn how the amygdala processes emotions or how the first violin produces sounds. But even the most detailed analysis of all brain regions does not tell us how the brain works as a whole - just as a complete list of instruments does not provide the score of a Beethoven symphony…

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