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Prefrontal Cortex transcranial Direct Current Stimulation via a Combined High Definition and Conventional Electrode Montage: A FEM modeling study. Dennis Q. Truong, Abhishek Datta , Jiansong Xu , Felipe Fregni , and Marom Bikson Neural Engineering Laboratory
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Prefrontal Cortex transcranial Direct Current Stimulation via a Combined High Definition and Conventional Electrode Montage: A FEM modeling study Dennis Q. Truong, AbhishekDatta, JiansongXu, Felipe Fregni, and MaromBikson Neural Engineering Laboratory Department of Biomedical Engineering, City College of the City University of New York, NY *Research supported by The Wallace Coulter Foundation
tDCS Basics • Typicallysubthreshold brain stimulation • Action potentials are not directly caused, rather excitability is enhanced or suppressed • Enhanced or Suppressed cortical excitability is due to polarity.
Heuristic Montages • Traditionally montages have been created by “rule of thumb” • Active Pad over a target region.
Heuristic Montages • Traditionally montages have been created by “rule of thumb” • Active Pad over a target region. M1
Heuristic Montages • Traditionally montages have been created by “rule of thumb” • Active Pad over a target region. Broca’s
Heuristic Montages • Traditionally montages have been created by “rule of thumb” • Active Pad over a target region. Wernicke’s
Heuristic Montages • Traditionally montages have been created by “rule of thumb” • Active Pad over a target region. Dorsal Lateral Prefronal Cortex (F8)
Heuristic Montages • Traditionally montages have been created by “rule of thumb” • Active Pad over a target region. • Return Pad is simply elsewhere. F8 - SO
tDCS is Polarity Sensitive • Both the “Active” and “Return” stimulate (enhanced or suppressed excitability)
An Alternative to ContralateralSupraorbital • Both the “Active” and “Return” stimulate (enhanced or suppressed excitability) “2x1” Hybrid
Heuristic Design is Limited • The location of the return pad effects current distribution.
Stimulation “over” is not Stimulation “of” • Peak Electric field may or may not be on be directly under the active electrodes
Stimulation “over” is not Stimulation “of” • Peak Electric field may or may not be on be directly under the active electrodes
Summary • Montage design does not obey a simple rule of thumb. • Active Electrodes do not necessarily cause peak field at the target. • Return Electrodes need to be carefully considered. • Big Picture: Clinicians could use better guidelines for montage designs. i.e. – database of montage models