Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Transcranial magnetic stimulation (TMS) modulates processing in the human brain and is therefore of interest as a treatment modality for neurologic conditions. During TMS administration, an electric current passing through a coil on the scalp creates a rapidly varying magnetic field that induces currents in the cerebral cortex. The effects of low-frequency (1 Hz), repetitive TMS (rTMS) on motor cortex cerebral blood flow (CBF) and tissue oxygenation in seven healthy adults, during/after 20 min stimulation, is reported. Noninvasive optical methods are employed: diffuse correlation spectroscopy (DCS) for blood flow and diffuse optical spectroscopy (DOS) for hemoglobin concentrations. A significant increase in median CBF (33%) on the side ipsilateral to stimulation was observed during rTMS and persisted after discontinuation. The measured hemodynamic parameter variations enabled computation of relative changes in cerebral metabolic rate of oxygen consumption during rTMS, which increased significantly (28%) in the stimulated hemisphere. By contrast, hemodynamic changes from baseline were not observed contralateral to rTMS administration (all parameters, p > 0.29). In total, these findings provide new information about hemodynamic/metabolic responses to low-frequency rTMS and, importantly, demonstrate the feasibility of DCS/DOS for noninvasive monitoring of TMS-induced physiologic effects. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)186National Institutes of Health [P30 NS045839, K01-NS060995, R01-NS060653, K24-NS058386, R24-HD050836, P41-EB015893]Fundacio Cellex Barcelona (TD)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Robert Wood Johnson Foundation/Harold Amos Medical Faculty Development ProgramNeuro-Cognitive Rehabilitation Research NetworkInstitute for Translational Medicine and Therapeutics, Clinical & Translational Science AwardsTranslational Biomedical Imaging Core at the University of PennsylvaniaFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)National Institutes of Health [P30 NS045839, K01-NS060995, R01-NS060653, K24-NS058386, R24-HD050836, P41-EB015893]FAPESP [FAPESP 2012/02500-8]