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BOLD‐fMRI response vs. transcranial magnetic stimulation (TMS) pulse‐train length: Testing for linearity
Author(s) -
Bohning Daryl E.,
Shastri Ananda,
Lomarev Mikhail P.,
Lorberbaum Jeffrey P.,
Nahas Ziad,
George Mark S.
Publication year - 2003
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.10271
Subject(s) - transcranial magnetic stimulation , functional magnetic resonance imaging , motor cortex , pulse (music) , auditory cortex , neuroscience , physics , psychology , stimulation , detector , optics
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. J. Magn. Reson. Imaging 2003;17:279–290. © 2003 Wiley‐Liss, Inc.