TY - JOUR
T1 - Paradoxical relationship between frequency selectivity and threshold sensitivity during auditory-nerve fiber development
AU - Fitzakerley, Janet L.
AU - McGee, Jo Ann
AU - Walsh, Edward J.
N1 - Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1998/6
Y1 - 1998/6
N2 - The acquisition of adultlike frequency selectivity is generally assumed to be tightly coupled to improvements in threshold sensitivity during cochlear development. In this study, frequency versus threshold (tuning) curves obtained from 1108 auditory-nerve fibers were used to investigate the relationship between tuning and threshold at characteristic frequency (CF) during postnatal development in kittens. At the earliest ages included in this study, sharpness was within the adult range, but thresholds were significantly higher than adult values. Tuning and thresholds improved along different exponential time courses that varied with CF. For units with CFs below 1 kHz, tuning curve slopes below CF matured earliest, followed by CF threshold, and then by slopes above CF. In contrast, for CFs above 1 kHz, the high-frequency slopes matured first, followed by threshold and then by slope below CF. One interpretation of these results is that tuning and thresholds are not tightly coupled in immature animals. Paradoxically, however, high- frequency slopes were correlated with threshold for individual units at all ages, suggesting that the relationship between tuning and threshold is maintained during development. This contradiction can be resolved by a developmental model that features a functional separation between cochlear nonlinearities and mechanical/electrical conversion.
AB - The acquisition of adultlike frequency selectivity is generally assumed to be tightly coupled to improvements in threshold sensitivity during cochlear development. In this study, frequency versus threshold (tuning) curves obtained from 1108 auditory-nerve fibers were used to investigate the relationship between tuning and threshold at characteristic frequency (CF) during postnatal development in kittens. At the earliest ages included in this study, sharpness was within the adult range, but thresholds were significantly higher than adult values. Tuning and thresholds improved along different exponential time courses that varied with CF. For units with CFs below 1 kHz, tuning curve slopes below CF matured earliest, followed by CF threshold, and then by slopes above CF. In contrast, for CFs above 1 kHz, the high-frequency slopes matured first, followed by threshold and then by slope below CF. One interpretation of these results is that tuning and thresholds are not tightly coupled in immature animals. Paradoxically, however, high- frequency slopes were correlated with threshold for individual units at all ages, suggesting that the relationship between tuning and threshold is maintained during development. This contradiction can be resolved by a developmental model that features a functional separation between cochlear nonlinearities and mechanical/electrical conversion.
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U2 - 10.1121/1.423055
DO - 10.1121/1.423055
M3 - Article
C2 - 9637032
AN - SCOPUS:0031801855
SN - 0001-4966
VL - 103
SP - 3464
EP - 3477
JO - Journal of the Acoustical Society of America
JF - Journal of the Acoustical Society of America
IS - 6
ER -