Dynamic modelling of electrical current distribution in the deep structure of the brain

Over the last decade various neurological disorders have been clinically treated using therapeutic deep brain stimulation (DBS). A fuller understanding of the role of modulating brain activity by electrical current will provide a rational basis for the optimisation of therapeutic effects. It remains unclear how the electrical current injected via the implanted depth electrodes is distributed locally or globally in the brain. This is largely because direct measurement of the distribution is difficult or almost impossible. A limited attempt has been made by some researchers to model the static conditions; however this does not include the dynamic features of the stimulation current. Additionally, the need for geometrically accurate finite element meshes of the adult human head is now becoming more acknowledged, and some investigations have been carried out to establish methodologies for their generation. This paper presents a new dynamic model of the whole human head using a geometrically accurate forward model that includes scalp, skull, CSF and brain with the correct conductivity parameters. Results of 10 Hz sinusoidal stimulation, simulating the therapeutic frequency ranging from 10 to 200Hz, in a case of DBS of the subthalamic nucleus for Parkinson's disease are presented. These results will be validated from measurements taken from both scalp and depth brain electrodes.