PET-based confirmation of orientation sensitivity of TMS-induced cortical activation in humans

Todd D. Krieg, Felipe S. Salinas, Shalini Narayana, Peter T Fox, David J. Mogul

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Background: Currently, it is difficult to predict precise regions of cortical activation in response to transcranial magnetic stimulation (TMS). Most analytical approaches focus on applied magnetic field strength in the target region as the primary factor, placing activation on the gyral crowns. However, imaging studies support M1 targets being typically located in the sulcal banks. Objective/hypothesis: To more thoroughly investigate this inconsistency, we sought to determine whether neocortical surface orientation was a critical determinant of regional activation. Methods: MR images were used to construct cortical and scalp surfaces for 18 subjects. The angle (θ) between the cortical surface normal and its nearest scalp normal for ∼50,000 cortical points per subject was used to quantify cortical location (i.e., gyral vs. sulcal). TMS-induced activations of primary motor cortex (M1) were compared to brain activations recorded during a finger-tapping task using concurrent positron emission tomographic (PET) imaging. Results: Brain activations were primarily sulcal for both the TMS and task activations (P < 0.001 for both) compared to the overall cortical surface orientation. Also, the location of maximal blood flow in response to either TMS or finger-tapping correlated well using the cortical surface orientation angle or distance to scalp (P < 0.001 for both) as criteria for comparison between different neocortical activation modalities. Conclusion: This study provides further evidence that a major factor in cortical activation using TMS is the orientation of the cortical surface with respect to the induced electric field. The results show that, despite the gyral crown of the cortex being subjected to a larger magnetic field magnitude, the sulcal bank of M1 had larger cerebral blood flow (CBF) responses during TMS.

Original languageEnglish (US)
Pages (from-to)898-904
Number of pages7
JournalBrain Stimulation
Volume6
Issue number6
DOIs
StatePublished - Nov 2013

Fingerprint

Transcranial Magnetic Stimulation
Electrons
Scalp
Magnetic Fields
Crowns
Fingers
Cerebrovascular Circulation
Motor Cortex
Brain

Keywords

  • Cerebral blood flow
  • Cortex
  • MRI
  • Orientation
  • PET
  • TMS

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)
  • Biophysics

Cite this

PET-based confirmation of orientation sensitivity of TMS-induced cortical activation in humans. / Krieg, Todd D.; Salinas, Felipe S.; Narayana, Shalini; Fox, Peter T; Mogul, David J.

In: Brain Stimulation, Vol. 6, No. 6, 11.2013, p. 898-904.

Research output: Contribution to journalArticle

Krieg, Todd D. ; Salinas, Felipe S. ; Narayana, Shalini ; Fox, Peter T ; Mogul, David J. / PET-based confirmation of orientation sensitivity of TMS-induced cortical activation in humans. In: Brain Stimulation. 2013 ; Vol. 6, No. 6. pp. 898-904.
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