I. Introduction
Electrical stimulation and recording of excitable biological entities, such as brain, retina or cochlea, are generally performed using separate electrodes for minimizing stimulus artifact contamination. Stimulus artifact is a synchronous noise that originates from electrode-electrolyte interface during and after application of a coulombic charge injecting stimulation pulse. Artifact signals can saturate high gain recording amplifiers for up to several milli-seconds [1], if recording is performed through the stimulation or the adjacent electrode contacts. Fig. 1(a) shows a typical stimulus artifact contaminated signal as obtained from a high gain neural amplifier. The stimulus artifact or the amplifier saturation duration is quite long and prevents reliable acquisition of short-latency evoked responses (bio-potentials) from living tissues that are being stimulated. Since stimulus artifact overlap neural responses substantially in both time and frequency domains [2], as shown in Fig. 1(b), it is challenging to eliminate this type of noise by means of filtering.
(a) A typical stimulus artifact contaminated signal obtained from a neural amplifier. (b) Power spectral density of neural and stimulation artifact signal [2].