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Simple metric for scaling motor threshold based on scalp-cortex distance: application to studies using transcranial magnetic stimulation
- Source :
- Journal of neurophysiology. 94(6)
- Publication Year :
- 2005
-
Abstract
- Transcranial magnetic stimulation (TMS) is a unique method in neuroscience used to stimulate focal regions of the human brain. As TMS gains popularity in experimental and clinical domains, techniques for controlling the extent of brain stimulation are becoming increasingly important. At present, TMS intensity is typically calibrated to the excitability of the human motor cortex, a measure referred to as motor threshold (MT). Although TMS is commonly applied to nonmotor regions, most applications do not consider the effect of changes in distance between the stimulating device and underlying neural tissue. Here we show that for every millimeter from the stimulating coil, an additional 3% of TMS output is required to induce an equivalent level of brain stimulation at the motor cortex. This abrupt spatial gradient will have crucial consequences when TMS is applied to nonmotor regions because of substantial variance in scalp-cortex distances over different regions of the head. Stimulation protocols that do not account for cortical distance therefore risk substantial under- or overstimulation. We describe a simple method for adjusting MT to account for variations in cortical distance, thus providing a more accurate calibration than unadjusted MT for the safe and effective application of TMS in clinical and experimental neuroscience.
- Subjects :
- Adult
Male
Adolescent
Physiology
medicine.medical_treatment
Stimulation
Brain mapping
Electromagnetic Fields
Cortex (anatomy)
medicine
Image Processing, Computer-Assisted
Humans
Brain Mapping
Scalp
General Neuroscience
musculoskeletal, neural, and ocular physiology
Motor Cortex
Human brain
Transcranial Magnetic Stimulation
Transcranial magnetic stimulation
body regions
medicine.anatomical_structure
nervous system
Electromagnetic coil
Brain stimulation
Sensory Thresholds
Calibration
Female
Psychology
Neuroscience
Motor cortex
Subjects
Details
- ISSN :
- 00223077
- Volume :
- 94
- Issue :
- 6
- Database :
- OpenAIRE
- Journal :
- Journal of neurophysiology
- Accession number :
- edsair.doi.dedup.....235ad4b91741ffd6bc829869faff85c0