P22.4 Investigating the mechanism of deep brain stimulation using a dynamic complex model of the head incorporated with a complete model of electrode

Abstract

Background: The use of deep brain stimulation (DBS) for clinical treatment for various neurological disorders, particularly movement disorders such as Parkinson’s disease is on the increase. However, the mechanism by which this electrical stimulation acts on neuronal activity is unclear. Experimental in situ investigation of the mechanism of DBS in animal models or patients has clear limitations due to the multi-factorial nature. Objectives: Our aim is to produce an accurate computational model to simulate the current flow produced by DBS. This will increase the understanding of the precise effects of the injected current on the surrounding neural tissue and allow us to predict optimum dynamic injection and measurement protocols required to maximise the effects of DBS in a defined region of the brain. Methods: We have developed a dynamic complex head model that incorporates the complete electrode model. This model takes into account the effects of the electrode contact impedance at the interface of the electrodes. The head model is based on a realistic FEM of a human head which incorporates an estimation of the head’s tissues conductivities. Results: The results from the model yield a fuller understanding of the three-dimensional current flow in the surrounding neuronal tissues. In particular, the model shows the distribution of electric field around electrode–brain interface (EBI), depending on the characteristic magnitude, rate, impedance, and waveform of brain pulsation. Therefore this shows how this physiological modulation affects the therapeutic effect of DBS. Conclusions: A number of research groups have presented results of the electrode interface for DBS. However the previous studies have not included the correct electrode model, limiting the validity of their simulations. Inaccurate estimation of this interface effect is particularly critical when considering the dynamic properties of the current distribution and hence the effects on the neural activity.