FREQUENCY SPECIFICITY OF THE HUMAN AUDITORY BRAIN-STEM AND MIDDLE LATENCY RESPONSES TO BRIEF TONES .2. DERIVED RESPONSE ANALYSES

This study investigated the frequency specificity of the auditory brai nstem (ABR) and middle latency (MLR) responses to 500- and 2000-Hz bri ef tones using narrow-band derived response analyses of the responses recorded in high-pass masking noise [Oates and Stapells, J. Acoust. Se c. Am. 102, 3597-3608 (1997)]. Stimuli were linear-and exact-Blackman- gated tones presented at 80 dB ppe SPI. Cochlear contributions to ABR wave V-V' and MLR wave Na-Pa were assessed by response amplitude profi les as a function of derived band center frequency. The largest amplit udes of waves V and Na-Pa occurred in the 500- and 707-Hz derived band s in response to the exact-Blackman- and linear-gated 500-Hz tones. Th e peak in the response amplitude profiles for wave V to both 2000-Hz s timuli was seen in the 2000-Hz derived band. For wave Na-Pa, the maxim a in the amplitude profiles occurred in the 2000- and 1410-Hz derived bands for the exact-Blackman-and linear-gated tones. Smaller cochlear contributions to the ABR/MLR were also present at 0.5-1 octave above a nd below the nominal stimulus frequencies. The ABR/MLR to 500- and 200 0-Hz 80 dB ppe SPL tones thus shows good frequency specificity, with n o significant differences in the frequency specificity of: (1) ABR ver sus MLR; (2) these evoked potentials to 500-versus 2000-Hz tones; and (3) responses to exact-Blackman-versus linear-gated tones. (C) 1997 Ac oustical Society of America. [S0001-4966(97)06312-1].