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Background Among transcranial electric stimulation (tES) parameters, personalizing the electrode geometry might help overcome the individual variability of the induced effects. Objective/hypothesis To test the need for electrode personalization, instead of a universal electrode for everyone, to induce neuromodulation effects on the bilateral primary motor cortex (M1) devoted to upper and lower limb representation. Methods By an ad-hoc neuronavigation procedure, we shaped the personalized electrode and positioned it matching the projection on the scalp of the individual central sulcus by a 2 cm strip, with total area of 35 cm 2 . The non-personalized electrode, i.e., equal for all subjects, was a 2 cm wide strip size-matched with the personalized electrode but shaped on a standard model fitting the curve passing through C3-CZ-C4 sites of the electroencephalographic (EEG) 10-20 International System. To test neuromodulation electrode-dependent efficacy, we induced a 20 Hz sinusoidal modulated current (transcranial alternating current stimulation, tACS) because it produces online effects. We simultaneously collected left and right hand and leg motor potentials (MEP) that were evoked by a rounded transcranial magnetic stimulation (TMS) coil. Through each electrode we delivered both real and sham stimulations. Results While cortical excitability during tACS increased during both the non-personalized and the personalized electrodes for the leg, the hand representation excitability enhancement was induced selectively when using the personalized electrode. The results were consistent bilaterally. Conclusions We documented that by using a personalized electrode it is possible to induce the neuromodulation of a predetermined extended cortical target, which did not occur with a non-personalized electrode. Our findings can help in building neuromodulation methods that might compensate for individual alterations across specific brain networks. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Repetitive Transcranial Magnetic Stimulation (rTMS) has been recently employed as a therapeutic strategy for stroke, although its effects on cerebral hemodynamics has been poorly investigated. This study aims to examine the impact of high frequency rTMS on cerebral vasomotor reactivity (VMR). Methods: Twenty-nine healthy subjects were randomly assigned to real (19) or sham 17-Hz rTMS, applied on primary motor cortex (M1) of the dominant hemisphere. All subjects underwent Transcranial Doppler of the middle cerebral arteries to evaluate mean flow velocity and VMR before (T 0) and within 10min (T 1) following rTMS. Four subjects underwent further VMR evaluations at 2 (T 2), 5 (T 3) and 24h (T 4) after rTMS. As a control condition, 10 subjects underwent real (5) or sham rTMS on calcarine cortex. In addition, five acute stroke patients underwent five daily rTMS sessions on the affected hemisphere mimicking a therapeutic trial. Results: Following real rTMS on M1 (p =0.002) and calcarine cortex (p <0.001) VMR decreased with respect to T 0 in both hemispheres, while no change was observed after sham rTMS (p >0.6). VMR tended to remain lower than T 0 until T 3. Cerebral VMR decreased independently of the stimulated side also in the patients’ group. Conclusions: High frequency rTMS reduces cerebral VMR, possibly as a secondary effect on autonomic control of cerebral hemodynamics. Significance: The effect of rTMS on cerebral hemodynamics should be carefully considered before proceeding toward a therapeutic application in stroke patients. [Copyright &y& Elsevier]