title: Effects of dipole position, orientation and noise on the accuracy of EEG source localization.
abstract: BACKGROUND
  The electroencephalogram (EEG) reflects the electrical activity in the brain on the surface of scalp. A major challenge in this field is the localization of sources in the brain responsible for eliciting the EEG signal measured at the scalp. In order to estimate the location of these sources, one must correctly model the sources, i.e., dipoles, as well as the volume conductor in which the resulting currents flow. In this study, we investigate the effects of dipole depth and orientation on source localization with varying sets of simulated random noise in 4 realistic head models.
  
  
  METHODS
  Dipole simulations were performed using realistic head models and using the boundary element method (BEM). In all, 92 dipole locations placed in temporal and parietal regions of the head with varying depth and orientation were investigated along with 6 different levels of simulated random noise. Localization errors due to dipole depth, orientation and noise were investigated.
  
  
  RESULTS
  The results indicate that there are no significant differences in localization error due tangential and radial dipoles. With high levels of simulated Gaussian noise, localization errors are depth-dependent. For low levels of added noise, errors are similar for both deep and superficial sources.
  
  
  CONCLUSIONS
  It was found that if the signal-to-noise ratio is above a certain threshold, localization errors in realistic head models are, on average the same for deep and superficial sources. As the noise increases, localization errors increase, particularly for deep sources.
authors.affiliation: Department of Physics, Dalhousie University, Halifax, NS, Canada. kwhittin@dal.ca
authors.forename: Kevin
authors.initials: K
authors.lastname: Whittingstall
authors.forename: Gerhard
authors.initials: G
authors.lastname: Stroink
authors.forename: Larry
authors.initials: L
authors.lastname: Gates
authors.forename: J F
authors.initials: JF
authors.lastname: Connolly
authors.forename: Allen
authors.initials: A
authors.lastname: Finley
mesh_terms: D016477:Artifacts; D001921:Brain / Q000502:physiology; D001931:Brain Mapping / Q000295:instrumentation / Q000379:methods*; D003198:Computer Simulation; D017097:Electric Impedance; D004566:Electrodes; D004569:Electroencephalography / Q000379:methods*; D006801:Humans; D008564:Membrane Potentials; D008953:Models, Anatomic; D016011:Normal Distribution; D010296:Parietal Lobe / Q000503:physiopathology; D012535:Scalp; D013499:Surface Properties; D013702:Temporal Lobe / Q000503:physiopathology