Stimulation artifact rejection

When a device stimulates the nervous system while recording — DBS, cortical or intracortical microstimulation, responsive neurostimulation, peripheral or transcranial stimulation — each pulse injects a large electrical transient, often orders of magnitude above the neural signal and capable of saturating the amplifier and its recovery transient. This is the central obstacle to bidirectional and closed-loop devices, because the biomarker or decode must be read from the same tissue that is being stimulated.

Countermeasures span hardware and algorithm: front-ends with fast artifact recovery, sample-and-hold or blanking that disconnects the amplifier during the pulse, high dynamic range to avoid saturation, and post-hoc template subtraction (the stereotyped pulse waveform is estimated and subtracted), interpolation across the blanked interval, or adaptive and matched filtering. Perfect removal is impossible when stimulation and signal overlap in time and band; residual artifact and the amplifier's nonlinear recovery limit how soon after a pulse neural activity can be trusted.