Impact of pulse duration in single pulse TMS

Area of Science:

• Neuroscience
• Electrophysiology
• Motor Cortex Excitability

Background:

• Transcranial magnetic stimulation (TMS) intensity is typically modulated by electrical field amplitude, keeping pulse duration constant.
• Investigating TMS pulse duration's impact on primary motor cortex excitability is crucial for understanding stimulation parameters.

Purpose of the Study:

• To examine the influence of two distinct TMS pulse durations on motor cortex excitability parameters.
• To compare the effects of standard versus longer TMS pulse durations on physiological measures.

Main Methods:

• Utilized a Magstim Bistim(2) stimulator to generate TMS pulses of varying durations.
• Measured resting and active motor thresholds, motor evoked potential recruitment curves, and cortical silent periods (cSP and iSP) in healthy volunteers.

Main Results:

• A 1.4 times longer TMS pulse duration decreased motor thresholds by 20% compared to standard pulses.
• No significant effect of pulse duration was observed on threshold-adjusted measures of cortical excitability.
• Longer TMS pulse durations led to a reduction in pulse-to-pulse variability for contralateral cortical silent periods (cSP).

Conclusions:

• TMS pulse strength can be adjusted via amplitude or pulse duration.
• Threshold-adjusted single-pulse measures of motor cortex excitability are not affected by TMS pulse duration.
• Longer TMS pulses may be beneficial for individuals with high motor thresholds and are relevant for comparing studies using different stimulator types.