Shape of the Pulse: Pulse Width and Current Direction Effects on Motor Evoked Potentials Using a Cobot-assisted...

Area of Science:

• Neuroscience
• Biomedical Engineering

Background:

• Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique.
• Controllable TMS (cTMS) with cobot-assisted neuronavigation allows precise coil placement.
• The system enables modulation of pulse width and current direction.

Purpose of the Study:

• Investigate the impact of current direction and pulse width on motor evoked potentials (MEPs).
• Evaluate the efficacy of different stimulation parameters using a cTMS device.

Main Methods:

• 30 healthy participants underwent MEP recording from the first dorsal interosseous muscle.
• Biphasic pulses with varying durations (280 μs, 160 μs) and directions (PA, AP) were used.
• 100 pulses at 110% resting motor threshold (RMT) were applied in three conditions.

Main Results:

• Stimulation was well-tolerated with no adverse events.
• Shorter pulse widths required less stimulation intensity for the same response, indicating higher efficiency.
• Anterior-posterior (AP) current direction proved more effective than posterior-anterior (PA) for MEPs at threshold.

Conclusions:

• TMS outcomes are significantly influenced by current direction and pulse width.
• Shorter pulses offer more energy-efficient stimulation protocols.
• Parameter optimization is crucial for enhancing TMS reliability and comparability in research and clinical settings.