Probing intrahemispheric interactions with a novel dual-site TMS setup

Area of Science:

• Neuroscience
• Neuroimaging
• Brain Stimulation

Background:

• Investigating effective brain connectivity between adjacent regions, such as the primary motor cortex (M1) and dorsal premotor cortex (PMd), presents spatial challenges.
• Standard dual-site transcranial magnetic stimulation (dsTMS) techniques face limitations when targeting brain areas in close proximity.

Purpose of the Study:

• To introduce and evaluate a novel dsTMS setup designed to overcome spatial restrictions when stimulating two adjacent brain regions.
• To assess the technical feasibility and in vivo performance of the new dsTMS configuration for probing brain effective connectivity.

Main Methods:

• A novel dsTMS setup combining two figure-of-eight coils was technically evaluated for induced electric fields using SimNIBS modeling.
• The setup was tested in 23 participants using a short-interval intracortical inhibition (SICI) protocol and by probing intrahemispheric PMd-M1 interactions.

Main Results:

• Technical evaluation showed no significant alterations in electric fields despite coil overlap.
• The dsTMS setup reliably elicited SICI and enabled feasible investigation of PMd-M1 interactions with a 6 ms inter-stimulus interval.
• Modulation of M1 output was observed, indicating successful probing of intrahemispheric connectivity.

Conclusions:

• The presented dsTMS setup offers a new approach for stimulating adjacent brain regions with reduced technical and spatial limitations.
• This advancement facilitates more accurate and repeatable targeting, potentially driving innovation in effective connectivity research.