TY - JOUR
T1 - Phase-locked responses to tones of chinchilla auditory nerve fibers
T2 - Implications for apical cochlear mechanics
AU - Temchin, Andrei N.
AU - Ruggero, Mario A.
N1 - Funding Information:
Many thanks to Philip Joris and Nigel Cooper for their helpful comments. We were supported by Grants from the NIH (DC-000419) and the Hugh Knowles Center.
PY - 2010/6
Y1 - 2010/6
N2 - Responses to tones with frequency ≤5 kHz were recorded from auditory nerve fibers (ANFs) of anesthetized chinchillas. With increasing stimulus level, discharge rate-frequency functions shift toward higher and lower frequencies, respectively, for ANFs with characteristic frequencies (CFs) lower and higher than ∼0.9 kHz. With increasing frequency separation from CF, rate-level functions are less steep and/or saturate at lower rates than at CF, indicating a CF-specific nonlinearity. The strength of phase locking has lower high-frequency cutoffs for CFs > 4 kHz than for CFs < 3 kHz. Phase-frequency functions of ANFs with CFs lower and higher than ∼0.9 kHz have inflections, respectively, at frequencies higher and lower than CF. For CFs > 2 kHz, the inflections coincide with the tiptail transitions of threshold tuning curves. ANF responses to CF tones exhibit cumulative phase lags of 1.5 periods for CFs 0.7-3 kHz and lesser amounts for lower CFs. With increases of stimulus level, responses increasingly lag (lead) lower-level responses at frequencies lower (higher) than CF, so that group delays are maximal at, or slightly above, CF. The CF-specific magnitude and phase nonlinearities of ANFs with CFs < 2.5 kHz span their entire response bandwidths. Several properties of ANFs undergo sharp transitions in the cochlear region with CFs 2-5 kHz. Overall, the responses of chinchilla ANFs resemble those in other mammalian species but contrast with available measurements of apical cochlear vibrations in chinchilla, implying that either the latter are flawed or that a nonlinear "second filter" is interposed between vibrations and ANF excitation.
AB - Responses to tones with frequency ≤5 kHz were recorded from auditory nerve fibers (ANFs) of anesthetized chinchillas. With increasing stimulus level, discharge rate-frequency functions shift toward higher and lower frequencies, respectively, for ANFs with characteristic frequencies (CFs) lower and higher than ∼0.9 kHz. With increasing frequency separation from CF, rate-level functions are less steep and/or saturate at lower rates than at CF, indicating a CF-specific nonlinearity. The strength of phase locking has lower high-frequency cutoffs for CFs > 4 kHz than for CFs < 3 kHz. Phase-frequency functions of ANFs with CFs lower and higher than ∼0.9 kHz have inflections, respectively, at frequencies higher and lower than CF. For CFs > 2 kHz, the inflections coincide with the tiptail transitions of threshold tuning curves. ANF responses to CF tones exhibit cumulative phase lags of 1.5 periods for CFs 0.7-3 kHz and lesser amounts for lower CFs. With increases of stimulus level, responses increasingly lag (lead) lower-level responses at frequencies lower (higher) than CF, so that group delays are maximal at, or slightly above, CF. The CF-specific magnitude and phase nonlinearities of ANFs with CFs < 2.5 kHz span their entire response bandwidths. Several properties of ANFs undergo sharp transitions in the cochlear region with CFs 2-5 kHz. Overall, the responses of chinchilla ANFs resemble those in other mammalian species but contrast with available measurements of apical cochlear vibrations in chinchilla, implying that either the latter are flawed or that a nonlinear "second filter" is interposed between vibrations and ANF excitation.
KW - Basilar membrane
KW - Cochlear apex
KW - Phase-frequency functions
KW - Rate-frequency functions
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U2 - 10.1007/s10162-009-0197-4
DO - 10.1007/s10162-009-0197-4
M3 - Article
C2 - 19921334
AN - SCOPUS:77954758864
VL - 11
SP - 297
EP - 318
JO - JARO - Journal of the Association for Research in Otolaryngology
JF - JARO - Journal of the Association for Research in Otolaryngology
SN - 1525-3961
IS - 2
ER -