An interdisciplinary team of physicists and neurophysiologists from the Max Planck Institute for Dynamics and Self-Organization in Göttingen and the Ruhr-Universität Bochum has now examined more closely the speed and threshold of action potentials in nerve cells of the cerebral cortex of the mammal brain. They were able to show that action potentials are initiated extremely rapid here. Although a single action potential lasts a millisecond, a stronger influx of sodium already sets in during the first 200 microseconds. The sodium channels appear to open almost simultaneously, so that sodium ions can flow into the cells very quickly and in large amounts. At the same time, however, the researchers found in their measurements that the threshold values at which the action potentials were initiated were very variable.
In order to understand what causes this unusual behavior, the scientists tried to recreate the behavior of the cells in computer simulations of Hodgkin-Huxley-type models. To their surprise, it turned out that a high variability of the threshold value and a rapid onset of the action potential cannot be unified in this model. Both characteristics behave like both sides of a seesaw. To obtain a high variability of the threshold value, the model requires a low speed of initiation of the action potential. A rapid onset is only obtained, when the variability of the threshold value is low.
In order to recreate the observed behavior of the nerve cells in computer simulations, Wolf and his colleagues postulated a new mechanism, which explains how the sodium channels n