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SUMMARY:Neuronal Current Decomposition via Vector Surface Ellipsoidal Harm
 onics - Dassios\, G (University of Patras)
DTSTART:20110824T104500Z
DTEND:20110824T113000Z
UID:TALK32473@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Electroencephalography (EEG) and Magnetoencephalography (MEG) 
 provide the two most efficient imaging techniques for the study of the fun
 ctional brain\, because of their time resolution. Almost all analytical st
 udies of EEG and MEG are based on the spherical model of the brain\, while
  studies in more realistic geometries are restricted to numerical treatmen
 ts alone. The human brain can best approximated by an ellipsoid with avera
 ge semi-axes equal to 6\, 6.5 and 9 centimeters. An analytic study of the 
 brain activity in ellipsoidal geometry though\, is not a trivial problem a
 nd a complete closed form solution does not seems possible for either EEG 
 or MEG. In the present work we introduce vector surface ellipsoidal harmon
 ics\, we discuss their peculiar orthogonality properties\, and finally we 
 use them to decompose the neuronal current within the brain into the part 
 that is detectable by the EEG and that is detectable by the MEG measuremen
 ts. The decomposition of a vector field in vec tor surface ellipsoidal har
 monics leads to three subspaces R\, D and T\, depending on the character o
 f the surface harmonics that they span this subspaces. We see that both\, 
 the electric field obtained from EEG and the magnetic field obtained from 
 MEG\, have no T-component. Furthermore\, the T-component of the neuronal c
 urrent does not influence the EEG recordings\, while the MEG recordings de
 pend on all three components of the current.\n
LOCATION:Seminar Room 1\, Newton Institute
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