Ingo Bojak
(Swinburne University of Technology)
Tuesday, May 24, 4.00pm
The Seminar Room, First Floor, Physics Building
The University of Adelaide
Electrocortical Rhythms and Anaesthesia
Abstract:
In 1924 Hans Berger placed an electrode on the head of his son, Klaus, and recorded the first human electroencephalogram (EEG). He went on to observe that a single rhythm - the alpha rhythm at 8-13 Hz - dominates the electrical activity of the "idle but awake" brain. Eight decades later a theoretical explanation is still lacking. We address the issue with a cortical mean field theory, treating the brain as a bio-physical system rather than as a biological computer. Simulations of the electrical activity of an entire human cortex are computed using parallel PC clusters (Swinburne Supercomputer and VPAC). Thereby the human EEG power spectrum, including the alpha rhythm, can be reproduced with physiologically plausible parameters. We show that the model predicts successfully the effects on the human EEG of tranquilizers and general anaesthetic (GA) agents. The latter is currently being developed into a patented "depth of anaesthesia" monitor for clinical use. Similarly GA-induced epileptic seizures may be explainable by a Hopf bifurcation along the relevant parameter trajectory. Our results uniquely bridge the gap between (sub)cellular neuron function and macroscopic brain activity.