This paper investigates the spatial distribution of the electric field and of the current density in the brain tissues induced by transcranial direct current stimulation of the primary motor cortex. A numerical method was applied on a realistic human head model to calculate these field distributions in different brain structures, such as the cortex, the white matter, the cerebellum, the hippocampus, the medulla oblongata, the pons, the midbrain, and the thalamus. The influence of varying the anode area, the cathode area, and the injected current was also investigated. An electrode area as the one typically used in clinical practice (i.e., both electrodes equal to 35 cm(2)) resulted into complex and diffuse amplitude distributions over all the examined brain structures, with the region of maximum induced field being below or close to the anode. Variations in either the anode or cathode area corresponded to changes in the field amplitude distribution in all the brain tissues, with the former variation producing more diffuse effects. Variations in the injected current resulted, as could be expected, in linearly correlated changes in the field amplitudes.

This study is a first step in better understanding the mechanisms underlying tsDCS.

Since there is not a configuration that is capable of achieving a stimulation both deep and focal, the selection of the most suitable coil settings for a specific clinical application should be based on a balanced evaluation between these two different needs.

In this paper, fetal exposure to uniform magnetic fields (MF) with different polarizations is quantified at 50 Hz. Numerical computations were performed on high-resolution pregnant models at 3, 7, and 9 months of gestational age (GA), that distinguish a high number of fetal tissues. Fetal whole-body and tissue-specific induced electric fields (E) and current densities (J) were analyzed as a function of both the extremely low frequency magnetic field (ELF-MF) polarization and GA. Additionally, the induced field variation due to changes in fetal position was analyzed by means of two new pregnant models. The uncertainty budget due to the grid resolution was also calculated. Finally, the compliance of the fetal exposure to the ICNIRP Guidelines was checked. A fetal exposure matrix was built at 50 Hz, which could be used to further investigate possible interaction mechanisms between ELF-MF and the associated health risk. Some specific findings were: (1) the induced fields increased with GA; (2) the maxima E were found in skin and fat tissues at each GA; (3) fetal tissue-specific exposure was modified as a function of GA and polarization; (4) the change of the fetal position in the womb significantly modified the induced E in some fetal tissues; (5) the induced fields were in compliance with ICNIRP Guidelines and the results were quite below the permitted threshold limit.

Exposure to radiofrequency (RF) electromagnetic fields (EMFs) in indoor environments depends on both outdoor sources such as radio, television and mobile phone antennas and indoor sources, such as mobile phones and wireless communications applications. Establishing the levels of exposure could be challenging due to differences in the approaches used in different studies. The goal of this study is to present an overview of the last ten years research efforts about RF EMF exposure in indoor environments, considering different RF-EMF sources found to cause exposure in indoor environments, different indoor environments and different approaches used to assess the exposure. The highest maximum mean levels of the exposure considering the whole RF-EMF frequency band was found in offices (1.14 V/m) and in public transports (0.97 V/m), while the lowest levels of exposure were observed in homes and apartments, with mean values in the range 0.13–0.43 V/m. The contribution of different RF-EMF sources to the total level of exposure was found to show slightly different patterns among the indoor environments, but this finding has to be considered as a time-dependent picture of the continuous evolving exposure to RF-EMF.

No abstract

Recent studies have shown that the specific application of transcranial direct current stimulation (tDCS) over the cerebellum can modulate cerebellar activity. In parallel, transcutaneous spinal DC stimulation (tsDCS) was found to be able to modulate conduction along the spinal cord and spinal cord functions. Of particular interest is the possible use of these techniques in pediatric age, since many pathologies and injuries, which affect the cerebellar cortex as well as spinal cord circuits, are diffuse in adults as well as in children. Up to now, experimental studies of cerebellar and spinal DC stimulation on children are completely missing and therefore there is a lack of information about the safety of this technique as well as the appropriate dose to be used during the treatment. Therefore, the knowledge of electric quantities induced into the cerebellum and over the spinal cord during cerebellar tDCS and tsDCS, respectively, is required. This work attempts to address this issue by estimating through computational techniques, the electric field distributions induced in the target tissues during the two stimulation techniques applied to different models of children of various ages and gender. In detail, we used four voxel child models, aged between 5- and 8-years. Results revealed that, despite inter-individual differences, the cerebellum is the structure mainly involved by cerebellar tDCS, whereas the electric field generated by tsDCS can reach the spinal cord also in children. Moreover, it was found that there is a considerable spread toward the anterior area of the cerebellum and the brainstem region for cerebellar tDCS and in the spinal nerve for spinal direct current stimulation. Our study therefore predicts that the electric field spreads in complex patterns that strongly depend on individual anatomy, thus giving further insight into safety issues and informing data for pediatric investigations of these stimulation techniques.

Tinnitus is considered an auditory phantom percept. Recently, transcranial direct current stimulation (tDCS) has been proposed as a new approach for tinnitus treatment including, as potential targets of interest, either the temporal and temporoparietal cortex or prefrontal areas. This study investigates and compares the spatial distribution of the magnitude of the electric field and the current density in the brain tissues during tDCS of different brain targets. A numerical method was applied on a realistic human head model to calculate these field distributions in different brain structures, such as the cortex, white matter, cerebellum, hippocampus, medulla oblongata, pons, midbrain, thalamus, and hypothalamus. Moreover, the same distributions were evaluated along the auditory pathways. Results of this study show that tDCS of the left temporoparietal cortex resulted in a widespread diffuse distribution of the magnitude of the electric fields (and also of the current density) on an area of the cortex larger than the target brain region. On the contrary, tDCS of the dorsolateral prefrontal cortex resulted in a stimulation mainly concentrated on the target itself. Differences in the magnitude distribution were also found on the structures along the auditory pathways. A sensitivity analysis was also performed, varying the electrode position and the human head models. Accurate estimation of the field distribution during tDCS in different regions of the head could be valuable to better determine and predict efficacy of tDCS for tinnitus suppression.