How reliable is such a pattern? Do even minor changes in the neuronal communication produce a completely different pattern in the same way that a modification to a single contribution in a conversation could alter the message completely? Such behaviour is defined by scientists as chaotic. In this case, the dynamic processes in the brain could not be predicted for long. In addition, the information stored in the activity pattern would be gradually lost as a result of small errors. As opposed to this, so-called stable, that is non-chaotic, dynamics would be far less error-prone. The behaviour of individual neurons would then have little or no influence on the overall picture.
The new results obtained by the scientists in Gttingen have revealed that the processes in the cerebral cortex, the brain's main switching centre, are extremely chaotic. The fact that the researchers used a realistic model of the neurons in their calculations for the first time was crucial. When a spike enters a neuron, an additional electric potential forms on its cell membrane. The neuron only becomes active when this potential exceeds a critical value. "This process is very important", says Fred Wolf, head of the Theoretical Neurophysics research group at the Max Planck Institute for Dynamics and Self-Organization. "This is the only way that the uncertainty as to when a neuron becomes active can be taken into account precisely in the calculations".
Older models described the neurons in a very simplified form and did not take into account exactly how and under what conditions a spike arises. "This gave rise to stable dynamics in some cases but non-stable dynamics in others", explains Michael Monteforte from the Max Planck Institute for Dynamics and Self-Organization, who is also a doctoral student at the Gttingen Graduate School for Neurosciences and Molecular Biosciences (GGNB). It was thus impossible t
|Contact: Dr. Fred Wolf|