Multi-scale model of axonal and dendritic polarization by transcranial direct current stimulation in realistic head geometry

Aberra, Aman S.; Wang, Ruochen; Grill, Warren M.; Peterchev, Angel V.

doi:10.1016/j.brs.2023.11.018

Cited by 7 publications

(2 citation statements)

References 93 publications

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“…In addition, intra-subject studies have reported an intensity of 2 mA to be the most effective in generating modulation of cortical excitability in the [0.2,2] mA range (Chew et al 2015). Since the normal E-field component seems to better capture individual experimental variability, at least when considering a threshold of 0.15 V m −1 , our results may suggest that the neuromodulatory effects seen in practice may be induced by the normal E-field component, responsible for somatic depolarization, and not by the tangential component, which has been suggested to modulate the excitability of interneurons in recent multiscale computational studies (Chung et al 2022, Aberra et al 2023. Therefore, normal E-field may be the preferred E-field parameters used to design individualized dosing-based protocols.…”

Section: Individual Supra-threshold Stimulation Intensitiesmentioning

confidence: 76%

Addressing the sources of inter-subject variability in E-field parameters in anodal tDCS stimulation over motor cortical network

Franco-Rosado,

Callejón,

Reina-Tosina

et al. 2024

Phys. Med. Biol.

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Background:Although tDCS constitutes a non-invasive neuromodulation technique with promising results in a great variety of applications, its clinical implementation is compromised by the high inter-subject variability reported. This study aims to analyze the inter-subject variability in electric fields (E-fields) over regions of the cortical motor network under two electrode montages: the classical C3Fp2 and an alternative P3F3, which confines more the Efield over this region.Methods:Computational models of the head of 98 healthy subjects were developed to simulate the E-field under both montages. E-field parameters such as magnitude, focality and orientation were calculated over three regions of interest (ROI): M1S1, SMA and preSMA. The role of anatomical characteristics as a source of inter-subject variability on E-field parameters was addressed using linear mixed-effect models.Results:P3F3 showed a more confined E-field distribution over M1S1 than C3Fp2; the latter elicited higher E-fields over supplementary motor areas. Both montages showed high inter-subject variability, especially for the normal component over C3Fp2. Skin, bone and CSF ROI volumes showed a negative association with E-field magnitude irrespective of montage. Grey matter volume and montage were the main sources of variability for focality. The curvature of gyri was found to be significantly associated with the variability of normal E-fields.Conclusions:Computational modelling proves useful in the assessment of E-field variability. Our simulations predict significant differences in E-field magnitude and focality for C3Fp2 and P3F3. However, anatomical characteristics were also found to be significant sources of E-field variability irrespective of electrode montage.

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Section: Individual Supra-threshold Stimulation Intensitiesmentioning

confidence: 76%

Addressing the sources of inter-subject variability in E-field parameters in anodal tDCS stimulation over motor cortical network

Franco-Rosado,

Callejón,

Reina-Tosina

et al. 2024

Phys. Med. Biol.

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“…There are many applications where such analysis seems comprehensive, e.g., where the stimulation electrode is adjacent to an axon bundle (nerve). The relevance of dendrite stimulation [57]- [59] derives from several factors including their 1) essential role in all brain processing; 2) their comparable sensitivity to polarization as axons; 3) recognition that polarization below action potential threshold (sub-threshold stimulation) effects brain function.…”

Section: Discussionmentioning

confidence: 99%

Dorsal horn dendrite polarization during Spinal Cord Stimulation (SCS) predicted using the quasi-uniform-mirror assumption

Zannou,

Koochesfahani,

Russo

et al. 2024

Preprint

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While the mechanisms of Spinal Cord Stimulation are traditionally assumed to follow pacing of dorsal columns axons, the development of sub-paresthesia SCS and new waveforms has encouraged consideration of different cellular targets. Given their relative proximity to the stimulation electrodes and role in pain processing (e.g., synaptic processing and gate control theory), spinal cord dorsal horn interneurons may be direct targets of stimulation. We developed a novel computational modeling pipeline termed 'quasi-uniform-mirror assumption' and apply it to predict polarization of dorsal horn inter-neuron cell types (Islet type, Central type, Stellate/Radial, Vertical-like) to SCS. The quasi-uniform-mirror assumption allows prediction, for each cell type and location in the dorsal horn, the peak and axis of dendritic polarization as well as the impact of stimulation pulse width. For long pulse (dc), the peak polarization per mA of SCS with a bipolar montage were: Islet type 3.5 mV, Central type 2 mV, Stellate/Radial 1.4 mV, Vertical-like 2.5 mV. For Stellate/Radial the peak dendritic polarization was dorsal-ventral, and for Islet type Central peak dendrite polarization was in the rostral-caudal axis. For Islet type and Central type cells peak dendrite polarization was between stimulation electrodes, while for Stellate/Radial and Vertical-like peak dendrite polarization was under stimulation electrodes. The impact of pulse width depended on cell membrane time constants, which in the quasi-uniform-mirror assumption are uniform first-order. Assuming 1 ms time constant, for a 1 ms or 100 us pulse width, the peak dendrite polarization decreases (from the dc values) by ~33% and ~88%. These results suggest, for the conditions modeled, maximum polarization is of islet-cells in the superficial dorsal horn at locations between electrodes; applying 2 mA 1 ms pulse SCS, the peak islet-cell dendrite polarization is ~4.7 mV. Polarizations of a few mV have been shown to modulate synaptic processing through sub-threshold mechanisms.

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Effects of dendritic Ca2+ spike on the modulation of spike timing with transcranial direct current stimulation in cortical pyramidal neurons

Huang,

Wei,

Wang

et al. 2024

J Comput Neurosci

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Multi-scale model of axonal and dendritic polarization by transcranial direct current stimulation in realistic head geometry

Cited by 7 publications

References 93 publications

Addressing the sources of inter-subject variability in E-field parameters in anodal tDCS stimulation over motor cortical network

Addressing the sources of inter-subject variability in E-field parameters in anodal tDCS stimulation over motor cortical network

Dorsal horn dendrite polarization during Spinal Cord Stimulation (SCS) predicted using the quasi-uniform-mirror assumption

Effects of dendritic Ca2+ spike on the modulation of spike timing with transcranial direct current stimulation in cortical pyramidal neurons

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