Berlin 2005 – wissenschaftliches Programm
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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.