title: Slow-Frequency Pulsed Transcranial Electrical Stimulation for Modulation of Cortical Plasticity Based on Reciprocity Targeting with Precision Electrical Head Modeling.
abstract: In pain management as well as other clinical applications of neuromodulation, it is important to consider the timing parameters influencing activity-dependent plasticity, including pulsed versus sustained currents, as well as the spatial action of electrical currents as they polarize the complex convolutions of the cortical mantle. These factors are of course related; studying temporal factors is not possible when the spatial resolution of current delivery to the cortex is so uncertain to make it unclear whether excitability is increased or decreased with anodal vs. cathodal current flow. In the present study we attempted to improve the targeting of specific cortical locations by applying current through flexible source-sink configurations of 256 electrodes in a geodesic array. We constructed a precision electric head model for 12 healthy individuals. Extraction of the individual's cortical surface allowed computation of the component of the induced current that is normal to the target cortical surface. In an effort to replicate the long-term depression (LTD) induced with pulsed protocols in invasive animal research and transcranial magnetic stimulation studies, we applied 100 ms pulses at 1.9 s intervals either in cortical-surface-anodal or cortical-surface-cathodal directions, with a placebo (sham) control. The results showed significant LTD of the motor evoked potential as a result of the cortical-surface-cathodal pulses in contrast to the placebo control, with a smaller but similar LTD effect for anodal pulses. The cathodal LTD after-effect was sustained over 90 min following current injection. These results support the feasibility of pulsed protocols with low total charge in non-invasive neuromodulation when the precision of targeting is improved with a dense electrode array and accurate head modeling.
authors.affiliation: Electrical Geodesics, Inc., EugeneOR, USA; Department of Psychology, University of Oregon, EugeneOR, USA.
authors.forename: Phan
authors.initials: P
authors.lastname: Luu
authors.affiliation: Electrical Geodesics, Inc., Eugene OR, USA.
authors.forename: Easwara Moorthy
authors.initials: EM
authors.lastname: Essaki Arumugam
authors.affiliation: Electrical Geodesics, Inc., Eugene OR, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Anderson
authors.affiliation: Electrical Geodesics, Inc., Eugene OR, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Gunn
authors.affiliation: Electrical Geodesics, Inc., Eugene OR, USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Rech
authors.affiliation: Electrical Geodesics, Inc., EugeneOR, USA; NeuroInformatics Center, University of Oregon, EugeneOR, USA.
authors.forename: Sergei
authors.initials: S
authors.lastname: Turovets
authors.affiliation: Electrical Geodesics, Inc., EugeneOR, USA; Department of Psychology, University of Oregon, EugeneOR, USA.
authors.forename: Don M
authors.initials: DM
authors.lastname: Tucker
keywords: cortical plasticity; head tissue conductivity; transcranial alternating current stimulation; transcranial direct current stimulation; transcranial electrical stimulation; transcranial pulsed current stimulation