Recovery of the auditory brainstem response by sign-bit and conventional averaging

In evoked potential studies, such as measurement of the auditory brainstem response (ABR), the signal of interest is recovered from the noise background by averaging at least 1000 EEG segments, recorded in phase, with a repeated auditory signal. The possibility is examined that information about whether each sample point was positive or negative relative to a baseline (i.e., averaging the sign bit) would allow recovery of the ABR for clinical purposes. A demonstration is presented in which auditory brainstem responses based on the full 12 bits of a typical analog-to-digital converter (TA or true amplitude procedure) are compared to those based on a single bit (SB procedure). For the signal-to-noise (S/N) ratios associated with an ABR signal in EEG noise (i.e., in the range 0.01>or=S/N>or=0.5), the recovery of the ABR signal using the SB procedure is quite satisfactory. Since the SB procedure is much less demanding computationally than the TA procedure, and thus faster and less expensive, it could be useful for practical ABR recovery.