A high resolution assessment of the repeatability of relative location and intensity of transcranial magnetic stimulation-induced and volitionally induced blood oxygen level-dependent response in the motor cortex.
OBJECTIVE
Using functional magnetic resonance imaging, we assessed variation in location and intensity of blood oxygen level-dependent contrast associated with movements induced by transcranial magnetic stimulation or volition.


BACKGROUND
Anatomic location and within-subject repeatability of blood oxygen level-dependent responses induced by transcranial magnetic stimulation comprise critical information to the use of interleaved transcranial magnetic stimulation/functional magnetic resonance imaging as a neuroscience tool.


METHODS
Eleven healthy adults were scanned 3 times each at 1.5 T. Interleaved with functional magnetic resonance imaging, 1-Hz transcranial magnetic stimulation was applied over motor cortex. VOL was alternated with transcranial magnetic stimulation over the scans.


RESULTS
Intra-subject standard deviations in blood oxygen level-dependent locations ranged between 3 and 6 millimeters, allowing localization to subregions of the motor strip. Coil placement relative to blood oxygen level-dependent location varied more than blood oxygen level-dependent location (sdx = 9.5mm, sdy = 8.7 mm, sdz = 9.0mm) with consistent anterior displacement (dy = 21.8 mm, P = <0.025). Analysis of variance did not detect significant differences between transcranial magnetic stimulation and VOL blood oxygen level-dependent locations or intensities, in contrast to significant intensity differences detected in auditory blood oxygen level dependence.


CONCLUSIONS
The high repeatability of location of transcranial magnetic stimulation-induced blood oxygen level-dependent activation suggests that transcranial magnetic stimulation/functional magnetic resonance imaging stimulation can be used as a precise tool in investigation of cortical mechanisms. The similarity between VOL and transcranial magnetic stimulation suggests that transcranial magnetic stimulation may act through natural brain movement circuits.
Denslow
Stewart
S
Center for Advanced Imaging Research and Brain Stimulation Laboratories, Department of Radiology, Medical University of South Carolina, Charleston, South Carolina, USA.
Lomarev
Mikhail
M
Bohning
Daryl E
DE
Mu
Qiwen
Q
George
Mark S
MS
D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000098:blood supply* / Q000502:physiology*; D009068:Movement; D010100:Oxygen / Q000097:blood*; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D050781:Transcranial Magnetic Stimulation; D014836:Volition
D010100:Oxygen