Bilateral M1 tDCS selectively modulates dynamic large-scale brain states associated with sensorimotor control relative to sham stimulation

Transcranial direct current stimulation of the primary motor cortex is widely used to influence sensorimotor performance, yet its large-scale neural mechanisms remain unclear. This study examined how unilateral and bilateral stimulation of the primary motor cortex affect sensorimotor behavior and whole-brain dynamics. Twenty healthy adults participated in a double-blind crossover study that combined robotic motor tasks performed during stimulation (on-task) with resting-state functional magnetic resonance imaging acquired during stimulation (off-task).

We found that both unilateral and bilateral stimulation improved bimanual coordination compared to sham, with no difference between montages. Bilateral stimulation additionally increased proprioceptive variability in the left hand. On the neural level, only bilateral stimulation, as compared with sham, altered large-scale dynamics, increasing the occurrence rate of a frontoparietal and dorsal attention state and reducing transitions from a default mode-frontoparietal state to a thalamic-subcortical state.

These brain dynamics were associated with sensorimotor performance in an exploratory analysis, thereby potentially linking stimulation-sensitive CAPs to motor performance. The authors would like to kindly thank Dr. Benjamin Kalloch for his assistance with data curation, and to Ms.

Shaymaa Darawshy for her assistance with preprocessing of functional imaging data. This work was supported by the Max-Planck Partner Group funding scheme; by the Alon Scholarship for the Integration of Outstanding Faculty (Israeli Council for Higher Education), and by the Israeli Science Foundation (803/25). Grants were obtained by Dr.

Haya Salameh and Toni Muffel have contributed equally to this work. Department of Cognitive Sciences, Faculty of Social Sciences, School of Psychological Sciences, University of Haifa, Haifa, Israel Haya Salameh, Yvonne Serhan, Uri Hertz & Smadar Ovadia-Caro The Integrated Brain and Behavior Research Center (IBBRC), University of Haifa, Haifa, Israel Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany Toni Muffel, Maria Samara, Arno Villringer & Bernhard Sehm Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, USA Computational Imaging Research Lab, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria Comprehensive Center for Artificial Intelligence in Medicine, Medical University of Vienna, Vienna, Austria Department of Neurology, University Hospital at the Martine Luther University of Halle-Wittenberg, Halle, Germany Department for Neurology and Stroke Center, SRH Clinic Naumburg, Naumburg, Germany Correspondence to Bernhard Sehm or Smadar Ovadia-Caro.

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