FILTERING AND SPECTRAL CHARACTERISTICS OF AVERAGED AUDITORY BRAIN-STEM RESPONSE AND BACKGROUND-NOISE IN INFANTS

Filtering of electrode-recorded activity before averaging is used in e voked-potential measurements to reduce background noise under the assu mption that unwanted spectral components will be suppressed without su bstantially altering neural activity. Desired filter characteristics d epend on signal and noise spectra and filter choice can affect the val idity and efficiency of ABR measurement. Spectral characteristics of t he human auditory brain-stem response (ABR) change with subject age an d state and with the level and spectrum of the stimulus. Brain-stem ev oked potentials from infants comprise greater low-frequency spectral c omponents than do adult ABRs. Physiologic noise can also change with a ge of the subject. This study compares the effects of 30- and 100-Hz h igh-pass filters on ABR amplitude and response F-sp in full-term infan ts. Stimuli used to elicit ABRs are moderate- and low-level clicks and 500-Hz tone bursts. Spectral characteristics of the averaged ABR and the no-stimulus background noise from full-term infants are also chara cterized. Results indicate that (1) energy in the infant ABR is concen trated below 100 Hz and (2) a high-pass recording filter of 30 Hz reve als a larger-amplitude ABR and enhances the overall signal-to-noise ra tio as measured by F-sp as compared to a 100-Hz high pass. (C) 1995 Ac oustical Society of America.