BOLD-fMRI response vs. transcranial magnetic stimulation (TMS) pulse-train length: Testing for linearity

Daryl E. Bohning, Ananda Shastri, Mikhail P. Lomarev, Jeffrey P. Lorberbaum, Ziad Nahas, Mark S. George

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Purpose: To measure motor and auditory cortex blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) response to impulse-like transcranial magnetic stimulation (TMS) pulses as a function of train length. Materials and Methods: Interleaved with fMRI at 1.5 T, TMS pulses 0.3-msec long were applied at 1 Hz to the motor cortex area for thumb. Six subjects were studied in a TR = 1 second session administering trains of 1, 2, 4, 8, and 16 pulses, and a TR = 3 seconds session administering trains of 1, 2, 4, 8, 16, and 24 pulses. A simple hemodynamic model with finite recovery and saturation was used to quantitatively characterize the BOLD-fMRI response as a function of train length. Results: In both the activations directly induced in motor cortex by TMS and the indirect activations in auditory cortex caused by the sound of the TMS coil firing, the BOLD-fMRI responses to multiple pulses were well described by a summation of single-pulse impulse functions. Conclusion: Up to 24 discrete pulses, BOLD-fMRI response to 1 Hz TMS in both motor cortex and auditory cortex were consistent with a linear increase in amplitude and length with train length, possibly suggesting that stimuli of 1 to 2 seconds may be too long to represent impulses.

Original languageEnglish (US)
Pages (from-to)279-290
Number of pages12
JournalJournal of Magnetic Resonance Imaging
Volume17
Issue number3
DOIs
StatePublished - Mar 1 2003

Keywords

  • BOLD response linearity
  • Motor cortex
  • Train length
  • Transcranial magnetic stimulation (TMS)
  • fMRI

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