Localizing Function-specific Targets for Transcranial Magnetic Stimulation in the Absence of Navigation Equipment

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique that modulates neural activity in the brain. Studies have shown that rTMS can regulate neural plasticity, promote neural network reorganization, and has been widely applied to neuropsychiatric disorders such as stroke. Although some studies suggest that rTMS can aid in stroke rehabilitation, its efficacy remains uncertain, possibly because of limitations in the traditional localization of the hand motor hotspot. The hand motor hotspot is determined by motor evoked potentials (MEPs), which reflect the conductivity of the corticospinal or pyramidal tract, representing non-voluntary movement. In contrast, functional magnetic resonance imaging (fMRI) activation points from a motor task define function-specific targets, which involve both perception and motor execution, representing voluntary movement. Based on this, we propose the concept of function-specific targets -- targets identified through brain imaging techniques aimed at specific functions. Function-specific targets exhibit stronger and more extensive functional connectivity with brain regions related to motor cognition, potentially offering more effective regulatory effects than the hotspots. We explored and validated the modulatory effects of function-specific targets in previous study. However, institutions without navigation equipment are unable to utilize these function-specific targets. Therefore, we have developed a non-navigated localization method for function-specific targets, specifically designed to define and localize rTMS targets in the post-stroke ipsilateral hemisphere, addressing the challenges faced by institutions lacking navigation equipment when applying function-specific targeted rTMS.