Improved EEG source analysis using low-resolution conductivity estimation in a four-compartment finite element head model

• Published in: Human brain mapping Vol. 30; no. 9; pp. 2862 - 2878
• Main Authors: Lew, Seok, Wolters, Carsten H., Anwander, Alfred, Makeig, Scott, MacLeod, Rob S.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.09.2009; Wiley-Liss
• Subjects: Algorithms; Biological and medical sciences; Brain - anatomy & histology; Brain - physiology; brain and skull conductivity; Brain Mapping - methods; cerebrospinal fluid; Cerebrospinal Fluid - physiology; EEG; Electric Conductivity; Electrodiagnosis. Electric activity recording; Electroencephalography - methods; Evoked Potentials, Somatosensory - physiology; Finite Element Analysis; finite element method; Head - anatomy & histology; Head - physiology; Humans; Image Processing, Computer-Assisted - methods; in vivo conductivity estimation; Investigative techniques, diagnostic techniques (general aspects); Magnetic Resonance Imaging - methods; Male; Medical sciences; Nervous system; Physical Stimulation; Radiodiagnosis. Nmr imagery. Nmr spectrometry; realistic four-compartment head modeling; Scalp - anatomy & histology; Scalp - physiology; Signal Processing, Computer-Assisted; simulated annealing; Skull - anatomy & histology; Skull - physiology; Somatosensory Cortex - anatomy & histology; Somatosensory Cortex - physiology; somatosensory-evoked potentials; source analysis; Subarachnoid Space - physiology; T1- and PD-weighted MRI; Touch - physiology; Touch Perception - physiology; Young Adult; source analysis; Nervous system diseases; Head; Radiodiagnosis; Estimation; EEG; Central nervous system; Electrophysiology; Conductivity; Electroencephalography; somatosensory-evoked potentials; Cerebrospinal fluid; Nuclear magnetic resonance imaging; Modeling; Encephalon; Finite element method; in vivo conductivity estimation; Simulated annealing; Skull; T1- and PD-weighted MRI; Models; Somatosensory evoked potential; brain and skull conductivity; realistic four-compartment head modeling
• ISSN: 1065-9471; 1097-0193
• DOI: 10.1002/hbm.20714

Bioelectric source analysis in the human brain from scalp electroencephalography (EEG) signals is sensitive to geometry and conductivity properties of the different head tissues. We propose a low‐resolution conductivity estimation (LRCE) method using simulated annealing optimization on high‐resolution finite element models that individually optimizes a realistically shaped four‐layer volume conductor with regard to the brain and skull compartment conductivities. As input data, the method needs T1‐ and PD‐weighted magnetic resonance images for an improved modeling of the skull and the cerebrospinal fluid compartment and evoked potential data with high signal‐to‐noise ratio (SNR). Our simulation studies showed that for EEG data with realistic SNR, the LRCE method was able to simultaneously reconstruct both the brain and the skull conductivity together with the underlying dipole source and provided an improved source analysis result. We have also demonstrated the feasibility and applicability of the new method to simultaneously estimate brain and skull conductivity and a somatosensory source from measured tactile somatosensory‐evoked potentials of a human subject. Our results show the viability of an approach that computes its own conductivity values and thus reduces the dependence on assigning values from the literature and likely produces a more robust estimate of current sources. Using the LRCE method, the individually optimized four‐compartment volume conductor model can, in a second step, be used for the analysis of clinical or cognitive data acquired from the same subject. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.