A Novel Stimulus Artifact Suppression System Using An Impedance-based Template

The existence of large stimulus artifact (SA) can easily bury useful neural signals of small amplitude, making simultaneous neural recording and stimulation difficult. We propose a proof-of-concept system for suppressing the SA based on a template subtraction. Equivalent impedance model of the electrode-tissue interface and the neuron is first analyzed. This impedance model can be equivalent to the transfer function of the stimulus current to the artifact. The parameters of the impedance model are derived from the spectra values which are obtained by the Fast Fourier Transform (FFT). By multiplying the spectra of stimulus current and transfer function and then inverse FFT can get the template of the SA. The proposed method has been validated in a) a simulated Randles model made of discrete circuit components and b) platinum electrodes in vitro. The proposed system has 43 dB and 30.5 dB stimulus artifact suppression ratio in simulated model and in vitro test, respectively.