02 July 2008

The most detailed map of interneuronal connections

Swiss and American scientists have received the most detailed mapping of neural connections in the cerebral cortex to date. Scientists also managed to identify for the first time the zone in which the density of intersections of axons connecting different parts of the brain is the highest.

In their work, the staff of Indiana University, Harvard Medical School (USA), the University of Lausanne and the State Polytechnic School of Lausanne (Switzerland) applied an innovative method of brain research – the so-called diffuse spectral tomography (DSI). This method, based on mapping the probabilistic function of the diffusion density of water molecules in tissues, allows us to fix the spatial relationships between the processes of nerve cells – axons.

Until recently, the method of functional magnetic resonance imaging allowed scientists only to observe the activation of certain areas of the brain in response to various stimuli, but the structure of nerve fibers connecting these areas was studied mainly in animal models.

With the help of a new research technique, scientists were able to trace the path of millions of nerve cell processes and identify the zone of the highest density of intersections of these processes – so to speak, the central "communication node" of the brain.  As it turned out, in all the volunteers studied, it was located in the posterior medial part of the cortex of both hemispheres.
"This was not known before, this area interested scientists from a different point of view," explains one of the lead authors of the study Olaf Sporns, "For example, it was known that at rest this area consumes the most energy, but until recently we could not explain why this happens".

At the next stage of the study, scientists intend to find out how the structural relationships they have identified change as the brain ages, or as a result of injuries and neurodegenerative diseases.

The research report is published in the journal PLoS Biology.

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