Functional connectivity revealed by single-photon emission computed tomography (SPECT) during repetitive transcranial magnetic stimulation (rTMS) of the motor cortex.
OBJECTIVE
In the present study, we studied effects of 1 Hz repetitive transcranial magnetic stimulation (rTMS) over the left primary motor cortex (M1) on regional cerebral blood flow (rCBF) using single-photon emission computed tomography (SPECT).


METHODS
SPECT measurements were carried out under two experimental conditions: real and sham stimulation. In sham stimulation, to exclude other components besides currents in the brain in rTMS, we applied sound and electrical stimulation to the skin of the head. 99mTc-ethyl cysteinate dimer was injected during the real or sham stimulation. Images were analyzed with the statistical parametric mapping software (SPM99). Relative differences in adjusted rCBF between two conditions were determined by a voxel-by-voxel paired t test.


RESULTS
1 Hz rTMS at an intensity of 1.1 x active motor threshold evoked increase of rCBF in the contralateral (right) cerebellar hemisphere. Reduction of rCBF was observed in the contralateral M1, superior parietal lobule (most probably corresponding to PE area in the monkey) (Rizzolatti G, Luppino G, Matelli M. Electroenceph clin Neurophysiol 1998;106:283-296), inferior parietal lobule (PF area in the monkey (Rizzolatti et al., 1998)), dorsal and ventral premotor areas (dPM, vPM) and supplementary motor area (SMA).


CONCLUSIONS
Increase of rCBF in the contralateral cerebellum must reflect facilitatory connection between the motor cortex and contralateral cerebellum. Reduced rCBF in the contralateral M1 may be produced by transcallosal inhibitory effect of the left motor cortical activation. CBF decrease in the right PM, SMA and parietal cortex may reflect some secondary effects. Low frequency rTMS at an intensity of around threshold for active muscles can evoke rCBF changes.


CONCLUSIONS
We demonstrated that rCBF changes could be elicited even by low frequency rTMS at such a low intensity as the threshold for an active muscle. Combination of rTMS and SPECT is one of powerful tools to study interareal connection within the human brain.
Okabe
Shingo
S
Department of Neurology, Division of Neuroscience, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
Hanajima
Ritsuko
R
Ohnishi
Takashi
T
Nishikawa
Masami
M
Imabayashi
Etsuko
E
Takano
Harumasa
H
Kawachi
Takashi
T
Matsuda
Hiroshi
H
Shiio
Yasushi
Y
Iwata
Nobue Kobayashi
NK
Furubayashi
Toshiaki
T
Terao
Yasuo
Y
Ugawa
Yoshikazu
Y
D000328:Adult; D002560:Cerebrovascular Circulation; D004558:Electric Stimulation; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000033:anatomy & histology* / Q000098:blood supply / Q000502:physiology*; D009434:Neural Pathways; D015899:Tomography, Emission-Computed, Single-Photon; D050781:Transcranial Magnetic Stimulation