Cortical and subcortical brain effects of transcranial magnetic stimulation (TMS)-induced movement: an interleaved TMS/functional magnetic resonance imaging study.
BACKGROUND
To date, interleaved transcranial magnetic stimulation and functional magnetic resonance imaging (TMS/fMRI) studies of motor activation have not recorded whole brain patterns. We hypothesized that TMS would activate known motor circuitry with some additional regions plus some areas dropping out.


METHODS
We used interleaved TMS/fMRI (11 subjects, three scans each) to elucidate whole brain activation patterns from 1-Hz TMS over left primary motor cortex.


RESULTS
Both TMS (110% motor threshold) and volitional movement of the same muscles excited by TMS caused blood oxygen level-dependent (BOLD) patterns encompassing known motor circuitry. Additional activation was observed bilaterally in superior temporal auditory areas. Decreases in BOLD signal with unexpected post-task "rebounds" were observed for both tasks in the right motor area, right superior parietal lobe, and in occipital regions. Paired t test of parametric contrast maps failed to detect significant differences between TMS- and volition-induced effects. Differences were detectable, however, in primary data time-intensity profiles.


CONCLUSIONS
Using this interleaved TMS/fMRI technique, TMS over primary motor cortex produces a whole brain pattern of BOLD activation similar to known motor circuitry, without detectable differences from mimicked volitional movement. Some differences may exist between time courses of BOLD intensity during TMS circuit activation and volitional circuit activation.
Denslow
Stewart
S
Department of Radiology, Center for Advanced Imaging Research and Brain Stimulation Laboratories, Medical University of South Carolina, Charlestown, SC 29425, USA. denslows@musc.edu
Lomarev
Mikhail
M
George
Mark S
MS
Bohning
Daryl E
DE
D000328:Adult; D001921:Brain / Q000033:anatomy & histology / Q000098:blood supply* / Q000502:physiology / Q000528:radiation effects*; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009068:Movement / Q000528:radiation effects*; D009415:Nerve Net / Q000098:blood supply / Q000502:physiology / Q000528:radiation effects; D010100:Oxygen / Q000097:blood; D011930:Reaction Time / Q000528:radiation effects; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation
D010100:Oxygen