Modeling the current density generated by transcutaneous spinal direct current stimulation (tsDCS).

OBJECTIVE: Non-invasive transcutaneous spinal direct current stimulation (tsDCS) induces changes in spinal cord function in humans. Nonetheless, the current density (J) spatial distributions generated by tsDCS are unknown. This work aimed to estimate the J distributions in the spinal cord during tsDCS. METHODS: Computational electromagnetics techniques were applied to realistic human models, based on high-resolution MRI of healthy volunteers (a 26-years-old female adult model "Ella"; a 14years-old male adolescent model "Louis"; an 11years old female adolescent model "Billie"). Three electrode montages were modeled. In all cases, the anode was always over the spinal process of the tenth thoracic vertebra and the cathode was placed: (A) above the right arm; (B) over the umbilicus; (C) over Cz. The injected current was 3mA. The electrodes were conductors within rectangular sponges. RESULTS: Despite inter-individual differences, the J tends to be primarily directed longitudinally along the spinal cord and cauda equina with the region of higher amplitude influenced by the reference electrode position; on transversal sections, the J amplitude distributions were quite uniform. CONCLUSIONS: Our modeling approach reveals that the J generated by tsDCS reaches the spinal cord, with a current spread also to the muscle on the back and the spinal nerve. SIGNIFICANCE: This study is a first step in better understanding the mechanisms underlying tsDCS.

Computational modeling of transcranial direct current stimulation in the child brain: implications for the treatment of refractory childhood focal epilepsy.

Transcranial direct current stimulation (tDCS) was recently proposed for the treatment of epilepsy. However, the electrode arrangement for this case is debated. This paper analyzes the influence of the position of the anodal electrode on the electric field in the brain. The simulation shows that moving the anode from scalp to shoulder does influence the electric field not only in the cortex, but also in deeper brain regions. The electric field decreases dramatically in the brain area without epileptiform activity.

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

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 ±1cm 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.