Sign up & Download
Sign in

Impact of the gyral geometry on the electric field induced by transcranial magnetic stimulation

by Axel Thielscher, Alexander Opitz, Mirko Windhoff
NeuroImage ()

Abstract

The spatial extent of the effects of transcranial magnetic stimulation (TMS) on neural tissue is only coarsely understood. One key problem is the realistic calculation of the electric field induced in the brain, which proves difficult due to the complex gyral folding pattern that results in an inhomogeneous conductivity distribution within the skull. We used the finite element method (FEM) together with a high-resolution volume mesh of the human head to better characterize the field induced in cortical gray matter (GM). The volume mesh was constructed from T1-weighted structural magnetic resonance images to allow for an anatomically accurate modeling of the gyrification pattern. Five tissue types were taken into account, corresponding to skin, skull, cerebrospinal fluid (CSF) including the ventricles as well as cortical gray and white matter. We characterized the effect of the current direction on the electric field distribution in GM. Importantly, the field strength in GM was increased by up to 51% when the induced currents were perpendicular to the local gyrus orientation. This effect was mainly restricted to the gyral crowns and lips, but did not extend into the sulcal walls. As a result, the focality of the fields induced in GM was increased. This enhancement effect might in part underlie the dependency of stimulation thresholds on coil orientation, as commonly observed in TMS motor cortex studies. In contrast to the clear-cut effects of the gyrification pattern on the induced field strength, current directions were predominantly influenced by the CSF-skull boundary. ?? 2010 Elsevier Inc.

Cite this document (BETA)

Available from NeuroImage
Page 1
hidden
Page 2
hidden

Readership Statistics

66 Readers on Mendeley
by Discipline
 
 
 
by Academic Status
 
38% Ph.D. Student
 
18% Student (Master)
 
12% Post Doc
by Country
 
6% United States
 
6% Germany
 
3% Canada

Sign up today - FREE

Mendeley saves you time finding and organizing research. Learn more

  • All your research in one place
  • Add and import papers easily
  • Access it anywhere, anytime

Start using Mendeley in seconds!

Already have an account? Sign in