Ontogeny of 2f1-f2 acoustic and cochlear microphonic distortion products

Abstract

The development of the acoustic distortion product (ADP) and cochlear microphonic distortion product (CMDP) 2f1-f2 was studied in pigmented rats, beginning 10 days after birth (p10). Both the ADP and CMDP were measured as a function of stimulus frequency (1.04 to 10.24 kHz with an f2/f1 ratio of 1.25) and level (20 to 80 dB SPL). The onset of the ADP occurred first at f2=5.12 kHz (p11–13), then at higher and lower frequencies. The amplitude of the ADP also matured first at f2=5.12 kHz (p17–18). This result is similar to the earlier work [S. J. Norton etal., Hear. Res. 51, 73–92 (1991); C. M. Henley etal., Hear. Res. 43, 141–148 (1989); M. Lenoir and J.-L. Puel, Hear Res. 29, 265–271 (1987)]. The onset and maturation of the DMDP was similar to ADP’s, except at lower frequencies where the CMDP developed somewhat earlier. There is a strong correlation in amplitudes of the ADPs and CMDPs across ages, consistent with the hypothesis that the ADP and CM DP may be linked to the same process [D. T. Kemp and A. M. Brown, Hear. Res. 13, 39–46 (1984)].