Effect of fat and muscle tissue conductivity on cortical currents - a tDCS study

Cortical current density distribution induced by tDCS has been assessed using an anatomically accurate high resolution finite element head model. The study examines the influence of low conductive fat tissue and muscle layers on cortical modulation. Comparison between commonly used 5 layers and proposed 7 layers head model has been carried out using statistical matrices (RDM, MAG and CC). Results indicate that fat and muscle tissue have a profound effect on cortical current distribution. These layers reduce the effective volume of scalp, thus leading to a reduction in the preferential current pathways around scalp. These findings support the need of more complex head models so that more accurate estimates can be made on the effects of cortical current stimulation on neurons.