Low voltage bifocal electrical stimulation of the motor cortex

Area of Science:

• Neuroscience
• Electrophysiology
• Motor Control

Background:

• Non-invasive cerebral motor area stimulation typically uses magnetic or high-voltage electrical methods requiring specialized equipment.
• Existing techniques present limitations for routine use in electrophysiological laboratories.

Purpose of the Study:

• To standardize a method for bifocal stimulation of the motor cortex using low-voltage conventional electrical stimulators.
• To establish a routine, accessible method for motor cortex stimulation in electrophysiological settings.

Main Methods:

• A novel bifocal stimulation technique was developed using surface electrodes (Cz as cathode, 8 cm lateral on the bimetal line as anode) with Xylocaine infiltration.
• Stimulation involved rectangular pulses of 150 microseconds duration and 200-250 Volts intensity.
• Motor evoked potentials (MEPs) were recorded from the opponens pollicis muscle during slight voluntary contraction, with MEP latency and central motor conduction time (CMCT) calculated.

Main Results:

• The study successfully standardized a low-voltage bifocal motor cortex stimulation method.
• MEP latency showed a significant relationship with age and height in normal subjects.
• Equations were derived to express normal inter-side variability for MEP latency and CMCT.

Conclusions:

• The developed method offers a practical and routine approach for bifocal motor cortex stimulation in electrophysiological laboratories.
• The findings provide normative data for MEP latency and CMCT, accounting for age and height.
• This technique enhances the accessibility and applicability of motor cortex stimulation studies.