Digital zero-phase-shift filtering of short-latency somatosensory evoked potentials.

Short-latency somatosensory potentials evoked by median nerve stimulation were averaged after analogue bandpass of 30-3000 Hz and then filtered by a zero-phase-shift digital filter with bandpass of 200-1500 Hz. Both near- and far-field potentials recorded by scalp to scalp, ear and extracephalic references were enhanced, without temporal distortion or the introduction of spurious peaks. Components were identified at the same or similar peak latencies as reported by other investigators. Zero-phase-shift digital filtering may increase the usefulness of recording short-latency somatosensory potentials.