How 100 Billion Neurons Produce a Clear Thought in Your Brain

Saturday, January 17, 2015

How 100 Billion Neurons Produce a Clear Thought in Your Brain

 Neuroscience
We have approximately 100 billion nerve cells in our brains, all of which communicate with one another. Why do they lead to clear thoughts or purposeful actions instead of mere gibberish? The reason lies, among other things, in a small group of inhibitory nerve cells that can use the messenger GABA to curb the activity of other nerve cells, scientists say.




Neuroscientists Dr. Michael Strüber and Dr. Marlene Bartos of the University of Freiburg  together with their Viennese colleagues Peter Jonas have found that the distances between communicating cells in the regulation of brain networks plays a role in our brainès ability to concentrate and produce clear thoughts.

The research was recently published in the current issue of the journal Proceedings of the National Academy of Sciences (PNAS).

GABA is is released at the synapses, from a specialized extension of the inflammatory cells, the axons. The messenger substance causes an electric signal in the receiving target cells.

basket cells
Hippocampal basket cells (magenta) and granule cells (green) with a schematic illustration of the distance-dependent inhibition. Image Source- Michael Strüber
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A particular subspecies of the GABA-releasing cells form the so-called basket cells. They are known to have a strong inhibitory effect on brain circuitry. One reason for this is the fact that basket cells have a long and widespread axon, with which they can control hundreds to thousands of sometimes far-flung target cells. Until now it was not clear whether all these target cells underwent the same signalling or whether long distances of the target cells of the GABA-releasing glomerulus complicated the signal accuracy.

By using the patch-clamp technique, which measures the current at individual cells, the team found that the further away a target cell is, the smaller and longer are their electrical signals. In pharmacological and electrophysiological experiments and detailed microscopic studies, neuroscientists have shown that the more distant the target basket cell axon, the fewer synapses for the connection, and that in these synapses other GABA-sensing proteins are found.

What could be the reason for such a complicated structure? To answer his question, the scientists have studied the effects of such a distance-dependent inhibition in computer simulation of neural networks.

Contrary to expectations, the weakening inhibition enables the basket cells to precisely control the activity of a large number of nerve cells and thus to synchronize them. The synchronization of entire brain areas leads to rhythmic brain activities like gamma oscillations, which serve a crucial function in higher mental processes.

The new approach is a distance-dependent inhibition could be an important component in the regulation of brain networks that allows a thought arises from the activity of 100 billion individual, but connected neurons.


SOURCE  University of Freiburg

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