A near infra-red spectroscopy study of the effects of pre-frontal single and paired pulse transcranial magnetic stimulation

ObjectiveConcentration changes in hemoglobin following single and paired pulse (2 and 15 ms inter-stimulus interval) transcranial magnetic stimulation (TMS) was investigated using near infra-red spectroscopy (NIRS).MethodsTMS was delivered to left pre-frontal cortex at typical intensities used in neuroscience research and concentrations of deoxyhemoglobin (Hb), oxyhemoglobin (HbO) and total hemoglobin (HbT) were measured.ResultsSignificant drops in concentration of HbO and HbT were observed and while there was no effect of the different pulse types on amplitude, there was a difference in the time taken to return to baseline.ConclusionsThe changes observed imply that in pre-frontal cortex, the different TMS pulse types result in differential effects on oxygen consumption.SignificanceThis study aids our understanding of the physiological effects of single and paired pulse TMS.