Closed-loop neuromodulation requires recording design to have high gain and low noise to capture sub-mV neural signals but artifacts exceeding 1 V saturates conventional recording system. Artifact needs to be removed before amplification to avoid data loss.
We developed a custom chip to leverage the differing propagation speed between artifact and neural response to remove artifacts before they saturate the amplifier. The artifact travels in tissue as electro-magnetic waves at a speed of 3*10^7 m/s while the neural signal travels at a much slower speed at around 10m/s. The 5 orders of speed difference provide a robust basis for selective removal.