Cortical recording with silicon microelectrodes: model-based analysis of contact dimension and encapsulation changes on recorded waveforms

Brain machine interfaces represent an emerging area of neurotechnology with both basic science and clinical applications. We developed a model of intracortical microelectrode recording to address the role of contact dimensions, tissue encapsulation, and neuron position on the time course and amplitude of the voltage records. We used a multi-compartment cable model of a 3D reconstruction of a layer V cortical pyramidal neuron to determine transmembrane currents generated during action potential signaling. We coupled the neuron model to finite element models (FEM) of microelectrodes in a cortical tissue medium. The neuronal currents were applied to the FEM and the voltage record at the contact was determined as a function of time. Our results show that the recorded waveform is relatively independent of typical contact sizes (<1000 mum²), but local inhomogeneities in the tissue medium can substantially enhance or suppress signal amplitude. Extensions of these analyses will enable development of silicon-substrate electrodes with optimized contact shape and distribution to achieve specific recording objectives