title: Personalizing the Electrode to Neuromodulate an Extended Cortical Region.
abstract: BACKGROUND
  Among transcranial electric stimulation (tES) parameters, personalizing the electrode geometry might help overcome the individual variability of the induced effects.
  
  
  OBJECTIVE
  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.
authors: Laboratory of Electrophysiology for Translational neuroScience (LET'S) - ISTC - CNR, Department of Neuroscience, Fatebenefratelli Hospital, Rome, Italy; Institute of Neurology, Department of Geriatrics, Neurosciences & Orthopaedics, Catholic University of Sacred Heart, Rome, Italy.
authors: A
authors: A
authors: Cancelli
authors: Laboratory of Electrophysiology for Translational neuroScience (LET'S) - ISTC - CNR, Department of Neuroscience, Fatebenefratelli Hospital, Rome, Italy; Department of Neuroscience and Imaging, G. d'Annunzio University of Chieti - Pescara, Italy.
authors: C
authors: C
authors: Cottone
authors: AFaR Division, Fatebenefratelli Foundation for Health Research and Education, Department of Neuroscience, Fatebenefratelli Hospital, Rome, Italy.
authors: M
authors: M
authors: Di Giorgio
authors: Department of Physiology and Pharmacology, Neuroimaging Laboratory, University of Rome "Sapienza", Italy.
authors: F
authors: F
authors: Carducci
authors: Laboratory of Electrophysiology for Translational neuroScience (LET'S) - ISTC - CNR, Department of Neuroscience, Fatebenefratelli Hospital, Rome, Italy; Department of Neuroimaging, IRCCS San Raffaele Pisana, Rome, Italy. Electronic address: franca.tecchio@cnr.it.
authors: F
authors: F
authors: Tecchio
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D004566:Electrodes; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation; D012535:Scalp / Q000502:physiology; D065908:Transcranial Direct Current Stimulation / Q000295:instrumentation*; D050781:Transcranial Magnetic Stimulation / Q000379:methods
keywords: Cortical target; Electrode personalization; Neuronavigation; Transcranial alternating current stimulation (tACS)