Background and Aim
Transcranial magnetic stimulation has advanced our knowledge of cortical physiology. Paired-pulse TMS allows explore intra-cortical facilitation (ICF), but the mechanism remains undetermined. Repetitive spinal motor neuron discharges (repMNDs) could contribute to ICF, which can be explored by the quadropulse (QuadS) and quintopulse stimulation (QuintS) technique (1). The objective was to establish a novel stimulation setup combining the paired-pulse stimulation paradigm with QuadS and QuintS. The ulterior objective is to explore the role of repMNDs in intracortical facilitation.
Methods
In our study we intended to find a method to measure the repMNDs in intracortical facilitation (ICF) established by the paired-pulse TMS paradigm. For this purpose, we combined the paired-pulse paradigm (PP) (2)with the quadropulse and quintopulse stimulation techniques (QuadS and QuintS) to quantify the repMNDs (1). The challenge was to set up the stimulation protocol combining multiple stimulators in a predefined sequence order and to randomize the stimulation conditions. The major challenge arose form the technical specificities of the various devices which had to be defined and explored to allow precise timing of the sequential stimuli.
Results
LabVIEW triggers the various stimulators in a sequential order, according to the experimental conditions, and acquires the data for off-line analysis. The stimulators are the Magstim BiStim2 and the 2002 (needed for the paired-pulse paradigm) TMS device for the motor cortex stimulation, the Grass S88 stimulator for the ulnar nerve stimulation at the wrist and the Digitimer DS7AH stimulator for the brachial plexus stimulation at the Erb's point. We use the ENMG-Viking Select IV instrument for the MEP recording. The experimental stimulation conditions are applied in a randomized order.
Conclusions
This novel stimulation protocol combines the paired-pulse stimulation and the TST, QuadS and QuintS to explore whether repMNDs contribute to the intracortical facilitation.