Modelling the electric field and the current density generated by cerebellar transcranial DC stimulation in humans

https://doi.org/10.1016/j.clinph.2013.09.039Get rights and content

Highlights

  • We evaluated the electric field and the current density spatial distribution of cerebellar tDCS in different brain regions.

  • We used computation method applied to realistic human model of different age and sex.

  • We showed that the strongest electric field and current density amplitudes occur mainly in the cerebellum.

Abstract

Objective

Transcranial Direct Current Stimulation (tDCS) over the cerebellum (or cerebellar tDCS) modulates working memory, changes cerebello-brain interaction, and affects locomotion in humans. Also, the use of tDCS has been proposed for the treatment of disorders characterized by cerebellar dysfunction. Nonetheless, the electric field (E) and current density (J) spatial distributions generated by cerebellar tDCS are unknown. This work aimed to estimate E and J distributions during cerebellar tDCS.

Methods

Computational electromagnetics techniques were applied in three human realistic models of different ages and gender.

Results

The stronger E and J occurred mainly in the cerebellar cortex, with some spread (up to 4%) toward the occipital cortex. Also, changes by ±1 cm in the position of the active electrode resulted in a small effect (up to 4%) in the E and J spatial distribution in the cerebellum. Finally, the E and J spreads to the brainstem and the heart were negligible, thus further supporting the safety of this technique.

Conclusions

Despite inter-individual differences, our modeling study confirms that the cerebellum is the structure mainly involved by cerebellar tDCS.

Significance

Modeling approach reveals that during cerebellar tDCS the current spread to other structures outside the cerebellum is unlike to produce functional effects.

Introduction

Transcranial Direct Current Stimulation (tDCS) is a non-invasive technique that modulates brain excitability (Priori, 2003, Nitsche and Paulus, 2011, Brunoni et al., 2012). tDCS over the cerebellum (or cerebellar tDCS) influences working memory (Ferrucci et al., 2008) and the processing of negative facial emotion (Ferrucci et al., 2012), motor control (Jayaram et al., 2012), and cerebello-cerebral connections (Galea et al., 2009) in healthy subjects. Cerebellar tDCS has also been recently proposed for the treatment of cerebellar disorders (Manto, 2008).

Among the open issues concerning cerebellar tDCS, the electric current density (J) and the electric field (E) that cross the skull and reach the cerebellum remain unknown. We therefore aimed to evaluate the electric quantities induced within the skull by cerebellar tDCS by using computational electromagnetic techniques on three realistic human models (of different age and sex), allowing to analyze current flow through the brain, the cerebellum and the brainstem. This could be of some help particularly in the investigation about the possible involvement of the cerebral cortex during cerebellar stimulation. Moreover, this study could provide answer to possible concerns about the safety of this tDCS application, providing information about the electric field in the brainstem and the heart.

Section snippets

Methods

Simulations were conducted using the simulation platform SEMCAD X (by SPEAG, Schmid & Partner Engineering, AG, Zurich, Switzerland, www.speag.com), solving the Laplace equation to determine the electric potential (φ) distribution inside the human tissues·(σφ)=0where σ is the electrical conductivity of the human tissues. The E and J field distributions were obtained by means of the following relations:E=-φJ=σE

Three human realistic models of the Virtual Family (Christ et al., 2010) were used.

Results

The higher J-field amplitudes generated by cerebellar tDCS were near the active electrode in the cerebellum at cortical level within the posterior lobe (Fig. 2). The J spread over the occipital cortex – quantified as the percentage of occipital volume where the amplitude of J-field is greater than 70% of the peak of J in the cerebellum – was only 4% for “Duke” and much less than 1% for “Ella” and “Billie”. The J slightly spreads also to the more anterior area of the cerebellum, particularly in

Discussions and conclusions

We here reported the first modeling study on the electric field generated by transcutaneous cerebellar DC stimulation in humans. Despite some inter-individual differences, cerebellar tDCS generates the highest electric field and current density below the stimulating electrode in the posterior cerebellum with a slight spread to other structures (Fig. 2). Within the cerebellum the current density distribution varies across different subjects, being maximum toward the more anterior part in the

Financial disclosures

Prof. Alberto Priori and Dr. Roberta Ferrucci reports no financial interests or potential conflicts of interests; Roberta Ferrucci and Alberto Priori are stakeholders of Newronika s.r.l., a spin-off company of the Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico and of the Università degli Studi di Milano.

Acknowledgment

The authors wish to thank Schmid & Partner Engineering AG (www.speag.com) for having provided the simulation software SEMCAD X.

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