Information stored in the activity patterns of cerebral cortex neurons is discarded at the surprisingly high rate of one bit per active neuron per second, scientists from the Max Planck Institute for Dynamics and Self-Organization at the University of Gottingen and the Bernstein Center for Computational Neuroscience Gpttingen have found.
The new results obtained by the scientists in Göttingen have also revealed that the processes in the cerebral cortex 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.”
Thanks to their more differentiated approach, the Göttingen-based researchers were able to calculate, for the first time, how quickly an activity pattern is lost through tiny changes; in other words, how it is forgotten. Approximately one bit of information disappears per active neuron per second. “This extraordinarily high deletion rate came as a huge surprise to us”, says Wolf. It appears that information is lost in the brain as quickly as it can be “delivered” from the senses.