Simulating Transcranial Direct Current Stimulation With a Detailed Anisotropic Human Head Model

Abstract

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique able to induce long-lasting changes in cortical excitability that can benefit cognitive functioning and clinical treatment. In order to both better understand the mechanisms behind tDCS and possibly improve the technique, finite element models are used to simulate tDCS of the human brain. With the detailed anisotropic head model presented in this study, we provide accurate predictions of tDCS in the human brain for six of the practically most-used setups in clinical and cognitive research, targeting the primary motor cortex, dorsolateral prefrontal cortex, inferior frontal gyrus, occipital cortex, and cerebellum. We present the resulting electric field strengths in the complete brain and introduce new methods to evaluate the effectivity in the target area specifically, where we have analyzed both the strength and direction of the field. For all cerebral targets studied, the currently accepted configurations produced sub-optimal field strengths. The configuration for cerebellum stimulation produced relatively high field strengths in its target area, but it needs higher input currents than cerebral stimulation does. This study suggests that improvements in the effects of transcranial direct current stimulation are achievable.

Cathodal Transcranial Direct Current Stimulation (tDCS) to the Right Cerebellar Hemisphere Affects Motor Adaptation During Gait

“…Relevant parameters include electrode size and placement, along with stimulation duration and intensity [12,51,52]. It is also unclear as to the spatial extent of the stimulation, although Rampersad [53] found largely focal effects when using the same configuration employed within this study. However, this is difficult to measure without sophisticated methods and is likely to vary across individuals.…”

Does transcranial direct current stimulation enhance cognitive and motor functions in the ageing brain? A systematic review and meta- analysis

“…A recent review of 61 studies applying tDCS to the DLPFC found a lack of consistency in outcomes making causal conclusions between DLFPC stimulation and a particular cognitive function difficult (Tremblay et al, 2014). One reason for the inconsistency is that tDCS appears to simultaneously modulate activity in a number of brain areas subserving a variety of cognitive functions with the maximum field strength being located some distance (20-40 mm) from the target area (e.g., DLPFC) (Rampersad et al, 2014).…”

“…Indeed, caution must be exercised because we cannot assume that the area receiving maximum stimulation is directly beneath the electrode, as the level of current delivered to different areas can vary substantially (Rampersad et al, 2014). Small drifts in the position of electrodes that can occur during a 20 min tDCS session can also significantly change the intensity and distribution of the current delivered to the brain (Woods et al, 2015).…”

Anodal Direct Current Stimulation of the Cerebellum Reduces Cerebellar Brain Inhibition but Does Not Influence Afferent Input from the Hand or Face in Healthy Adults

“…Furthermore, epidural anodal DCS of the cerebellum of rodents induces reorganisation of M1, reducing its excitability along with that of the motoneurons in the anterior horn of the spinal cord [53]. Investigations aimed at modelling the DCS electric field in humans demonstrated that maximal activation was localised to the targeted cerebellar hemisphere [54]. In contrast, repetitive TMS protocols in Parkinson's disease patients were found to alter metabolic activity in both cerebellar cortex and the deep cerebellar nuclei [55].…”