Transcranial magnetic stimulation intensities in cognitive paradigms

Area of Science:

• Neuroscience
• Cognitive Science
• Experimental Psychology

Background:

• Transcranial magnetic stimulation (TMS) is crucial for probing brain function by interfering with neural activity.
• Calibrating TMS intensity is a key methodological challenge, with motor threshold (MT) often used as a reference.
• The utility of MT for calibrating TMS in non-motor cognitive tasks remains under investigation.

Purpose of the Study:

• To evaluate the effectiveness of using individual motor thresholds (MT) to calibrate transcranial magnetic stimulation (TMS) intensities for cognitive paradigms.
• To determine if MT is a reliable predictor of TMS effects in non-motor brain regions.

Main Methods:

• Repetitive TMS (rTMS) was applied to the left posterior middle frontal gyrus (pMFG) or vertex control site.
• Stimulation was delivered at either a fixed intensity (40% maximum stimulator output) or 90% of individual MT.
• Participants performed a working memory task post-stimulation.

Main Results:

• Motor threshold (MT) predicted behavioral effects when TMS was applied at a fixed intensity.
• Individuals with lower MT showed greater behavioral changes under fixed-intensity stimulation.
• Individual adaptation of TMS intensity to MT did not produce stable or consistent effects.

Conclusions:

• Assessing MT is recommended as a general measure of cortical TMS susceptibility, even for non-motor applications.
• Current findings suggest caution when using individual MT to calibrate TMS for cognitive tasks.
• Further research is needed to refine TMS calibration methods for cognitive neuroscience.