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AKB: Biologische Physik

AKB 200: Poster Session II

AKB 200.19: Poster

Dienstag, 8. März 2005, 17:00–19:00, Poster TU C

Anomalous Dynamics of Action Potential Initiation in Cortical Neurons — •Björn Naundorf¹, Maxim Volgushev², Theo Geisel¹ und Fred Wolf¹ — ¹Max-Planck Institut für Strömungsforschung and Fakultät für Physik, Universität Göttingen, 37073 Göttingen — ²Abteilung Neurophysiologie, Ruhr-Universität Bochum

Action potential (AP) initiation in neurons is fundamental to information processing in the brain. In most neurons, AP initiation is mediated by the activation of fast, voltage-dependent sodium channels, canonically described by Hodgkin-Huxley (HH) type equations. Here we describe features of the dynamics of AP initiation which differ qualitatively from the predictions of the HH theory. We show that APs from neocortical neurons recorded in vivo and in vitro initiate much more rapidly than predicted by the steady state sodium activation curve, while at the same time APs are emitted in a very large voltage range. We then show that the two effects are mutually exclusive in HH type models and can not be resolved within the framework of the HH theory.
Using a phenomenological model, we further demonstrate that the observed AP onset dynamics has important consequences for the information processing capabilities of neocortical neurons. Rather than, as commonly believed, acting as a low pass filter, the model suggests that cortical neurons are specifically tailored to support highly transient signals, while suppressing slowly varying inputs.