I want to calibrate the resting motor threshold of the foot for my TMS study. For this, I will use the double cone coil (https://www.magstim.com/row-en/product/dcc/), while having EMG electrodes on the foot/leg, but I am unsure where/how to best attach them to get the best signal.
I am happy for any literature or best practices about electrode placement and in general, estimating the rMT of the foot using the double cone coil.
Never tried foot or leg - only ever experimented with hand muscles - but see G. Buccino,T, L. Riggio , G. Melli , F. Binkofski , V. Gallese , G. Rizzolatti Listening to action-related sentences modulates the activity of the motor system: A combined TMS and behavioral study Cognitive Brain Research 24 (2005) 355 – 363. They used leg muscles tibialis anterior and gastrocnemius.
Good luck.
I think it might help to consult the IFCN Guidelines and Recommendations, especially the article "A practical guide to diagnostic transcranial magnetic stimulation: Report of an IFCN committee" (https://www.sciencedirect.com/science/article/abs/pii/S1388245712000569) .
In it you can find information about the upper and lower limbs, thresholds and MEPs.
Good luck.
Hi Helena, usually the target muscle for the lower limb is the tibialis anterior muscle. The recording is a conventional belly-tendon bipolar montage. You localize the muscle by asking the subject to flex dorsally the foot as much as she/he can, you will see a bulge laterally to the tibia. Put the active electrode on the middle of the bulge and the reference distally, at the end of the bulge. In this way hte inter-electrode distance should be around 10 cm. I would advise to start looking for the hotspot with an active muscle, because with some subjects the resting threshold may be very high. I hope this is clear let me know if you need more info.
Thanks, that already helps a lot! However, we have a three electrode setup with an additional reference electrode. Do you have experience with this as well?
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