Blood flow and oxygenation changes due to low-frequency repetitive transcranial magnetic stimulation of the cerebral cortex

Abstract

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.

Sensitivity of near-infrared spectroscopy and diffuse correlation spectroscopy to brain hemodynamics: simulations and experimental findings during hypercapnia

“…6,16,78 Our simulations of contrast and CNR are in good qualitative agreement with these published results. The first report of simultaneous NIRS and DCS was published by Durduran et al, 6 who combined the two modalities in seven subjects performing a finger tapping task.…”

“…78 For an SD separation of 2.5 cm, they reported a median increase in CBF in the side ipsilateral to the stimulation of 33%, an increase in [HbO] of 5.4 μ M, a nonsignificant decrease in [HbR] of −0.15 μ M, and an increase in [HbT] of +5.1 μ M, after correction by wavelength-dependent DPFs. For+each subject, they report the maximum change measured by both modalities, as well as an error estimated by the standard deviation of the fluctuations during the rTMS duration.…”

The Electromagnetic Field Changes on Emotional-motivated Behavior in Genetically Epilepsy-prone Rats

“…Besides, Acoustic stimulation could promote the release of acetylcholine in the brainstem structures involved in the initiation of PGO waves. Perhaps, these influences mediated by changing in membrane ion channel permeability, which occur under the effect of low-frequency EMF (1,12) . Also, we suggest that EMF exposure on brain results changes in electric and current density fields, accompanied by modification of synaptic activity, modes of synchronous bursts of neuronal populations, ion dynamics, and other phenomena.…”

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“…Different protocols of rTMS have demonstrated therapeutic efficacies for various neuropsychiatric disorders such as depression, Parkinson's disease, dystonia, mania, tinnitus, and substance abuse. [2][3][4][5][6][7] Despite controversial findings on the therapeutic outcomes of this technique in different psychiatric disorders, researchers emphasize on developing this technique as an alternative or adjunctive modality for these disorders. Depression, different hallucinations, obsessive-compulsive disorder (OCD), posttraumatic stress disorder (PTSD), migraine tinnitus, substance abuse, and the main disorders have shown good treatment response to rTMS.…”