title: Stimulus intensity dependence of cerebral blood volume changes in left frontal lobe by low-frequency rTMS to right frontal lobe: A near-infrared spectroscopy study.
abstract: Repetitive transcranial magnetic stimulation (rTMS) has recently been widely employed for the investigation of brain function and treatment of psychiatric and neurological disorders. Although high and low stimulation frequencies are assumed to activate and deactivate brain function, respectively, the optimal parameters of rTMS for treatment of depression have been determined only on the basis of their clinical efficacy. In this study, we administered a 60-s low-frequency rTMS of three grades low intensities over the right dorsolateral prefrontal cortex (DLPFC) in 10 healthy volunteers, and monitored functional changes of the contralateral DLPFC by near-infrared spectroscopy (NIRS) during and immediately after rTMS. Obtained results demonstrated significant [oxy-Hb] decreases during rTMS, and significant differences in the time courses of [oxy-Hb] changes among three stimulus intensities, that is, [oxy-Hb] decreases were most prominent during the latter half of the stimulation and the first 30s of poststimulation only at 15mm condition (58% intensity). These results suggest that monitoring of brain functional changes due to rTMS using NIRS is useful for elucidating the brain mechanisms underlying the clinical effects of rTMS, and the effects of rTMS over contralateral DLPFC are obtained if the stimulus intensities are more than one-half of the motor thresholds.
authors.affiliation: Department of Psychiatry, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi 371-8511, Gunma, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Aoyama
authors.forename: Naoki
authors.initials: N
authors.lastname: Hanaoka
authors.forename: Masaki
authors.initials: M
authors.lastname: Kameyama
authors.forename: Masashi
authors.initials: M
authors.lastname: Suda
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Sato
authors.forename: Mingqiao
authors.initials: M
authors.lastname: Song
authors.forename: Masato
authors.initials: M
authors.lastname: Fukuda
authors.forename: Masahiko
authors.initials: M
authors.lastname: Mikuni
mesh_terms: D000328:Adult; D002560:Cerebrovascular Circulation / Q000502:physiology / Q000528:radiation effects; D003866:Depressive Disorder / Q000503:physiopathology / Q000628:therapy*; D004734:Energy Metabolism / Q000502:physiology / Q000528:radiation effects; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology / Q000528:radiation effects; D010108:Oxyhemoglobins / Q000032:analysis / Q000378:metabolism; D017397:Prefrontal Cortex / Q000098:blood supply* / Q000502:physiology / Q000528:radiation effects*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
chemical_list: D010108:Oxyhemoglobins