Auditory brain stem responses from human adults and infants: wave V tuning curves

Decrement in ABR wave V amplitude was measured in the presence of simultaneous tonal maskers. Probe stimuli were 1.0, 4.0, and 8.0-kHz third-octave-filtered clicks. Adults and 3-month-old infants served as subjects. The resultant amplitude-decrement functions for each tonal masker were fit with regression lines. The sound pressure level (SPL) required to reduce wave V to 50% of the unmasked probe amplitude was plotted for each masker to develop tuning curves. The tuning curves were quantified by calculations of tip-to-tail difference, Q 10, and SPL at maximum masker frequency (MMF). Tuning curves for adult and infant subjects were similar for the 1.0-kHz probe. For the high-frequency probes (4.0 and 8.0 kHz), smaller tip-to-tail differences and lower Q 10 values were observed for the infant subjects. Ranges of MMF level were similar across adult and infant subjects. For the 8.0-kHz probe, tuning curves from infant subjects consistently showed maximum masker frequencies which were lower than the probe.