Optimization of multifocal transcranial current stimulation for weighted cortical pattern targeting from realistic modeling of electric fields

By Giulio Ruffini, Michael D. Fox, Oscar Ripolles, Pedro Cavaleiro Miranda, Alvaro Pascual-Leone. NeuroImage, 2013

333 citations recorded by the source corpus.

Recently, multifocal transcranial current stimulation (tCS) devices using several relatively small electrodes have been used to achieve more focal stimulation of specific cortical targets. However, it is becoming increasingly recognized that many behavioral manifestations of neurological and psychiatric disease are not solely the result of abnormality in one isolated brain region but represent alterations in brain networks. In this paper we describe a method for optimizing the configuration of multifocal tCS for stimulation of brain networks, represented by spatially extended cortical targets. We show how, based on fMRI, PET, EEG or other data specifying a target map on the cortical surface for excitatory, inhibitory or neutral stimulation and a constraint of the maximal number of electrodes, a solution can be produced with the optimal currents and locations of the electrodes. The method described here relies on a fast calculation of multifocal tCS electric fields (including components normal and tangential to the cortical boundaries) using a five layer finite element model of a realistic head. Based on the hypothesis that the effects of current stimulation are to first order due to the interaction of electric fields with populations of elongated cortical neurons, it is argued that the optimization problem for tCS stimulation can be defined in terms of the component of the electric field normal to the cortical surface. Solutions are found using constrained least squares to optimize current intensities, while electrode number and their locations are selected using a genetic algorithm. For direct current tCS (tDCS) applications, we provide some examples of this technique using an available tCS system providing 8 small Ag/AgCl stimulation electrodes. We demonstrate the approach both for localized and spatially extended targets defined using rs-fcMRI and PET data, with clinical applications in stroke and depression. Finally, we extend these ideas to more general stimulation protocols, such as alternating current tCS (tACS).

Subfields: Cellular and Molecular Neuroscience, Cognitive Neuroscience, Neurology

View Paper: https://www.semanticscholar.org/paper/968f1bf497a95bc6f02b8918075a4dc4961240ef

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Citations in the corpus

Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines (2017, background): “Montages with (multiple) small electrodes do not affect the maximal V/m range with respect to safety considerations (Dmochowski et al. , 2011, Dmochowski et al. , 2013, Edwards et al. , 2013, Ruffini et al., 2014, Sadleir et al. , 2012).”
Combining non-invasive transcranial brain stimulation with neuroimaging and electrophysiology: Current approaches and future perspectives (2016, neutral): “For TCS, a fast relocation of stimulation electrodes is not possible, but multi-channel devices to rapidly switch for each electrode between EEG recording and TCS application mode are available (Ruffini et al., 2014).”
A technical guide to tDCS, and related non-invasive brain stimulation tools (2015, background): “Open questions remain about how to relate predicted current density or electric field distributions with neurophysiologic, cognitive and behavioral changes (Rahman et al., 2013, 2014; Ruffini et al., 2014).”
Targeting neural oscillations with transcranial alternating current stimulation (2021, background): “Alternatively, tACS could be conceptualized as enhancing an entire network of regions, and the stimulation montage could be selected to deliver the maximal electric field strength summated across the targeted network (Ruffini, 2018, 2014; Fischer, 2017).”
Closing the loop between brain and electrical stimulation: towards precision neuromodulation treatments (2023, methodology): “…approach for identi ﬁ cation of optimal parameters (e.g., improving tES ef ﬁ cacy by application of stimulation with the individual dominant frequency [144 – 146], phase [147, 148], or electrode placement [149] according to individual functional maps, as reported in previous studies).”
How structural and functional MRI can inform dual-site tACS parameters: A case study in a clinical population and its pragmatic implications. (2022, methodology): “sources of information such as EEG/MEG or fMRI data [45].”
fMRI Informed Montage Selection for Transcranial Electrical Stimulation: Frontoparietal Synchronization for Drug Cue Reactivity (2021, background): “In this context, target maps for multi-site tES can be defined based on various sources of information such as EEG/MEG or fMRI data [22].”