The Journal of Neuroscience, February 1, 2003, 23(3):1049
Seasonal Plasticity of Peripheral Auditory Frequency
Sensitivity
Joseph A.
Sisneros and
Andrew H.
Bass
Department of Neurobiology and Behavior, Cornell University,
Ithaca, New York 14853
Female midshipman fish (Porichthys notatus) use the
auditory sense to detect and locate vocalizing males during the
breeding season. Detection of conspecific vocal signals is essential to their reproductive success and can evoke strong phonotactic responses in gravid females but not in spent females that have released all of
their eggs. Here, we test the hypothesis that seasonal variation in
reproductive state affects the neurophysiological response properties
of the peripheral auditory system in female midshipman fish.
Iso-intensity responses of eighth nerve afferents from the sacculus,
the main auditory end organ of the inner ear, to individual tones were
measured for spike rate and vector strength (VS) of synchronization.
Most auditory saccular units in reproductive, summer females showed
robust temporal encoding up to 340 Hz, whereas nonreproductive winter
females showed comparable encoding only up to 100 Hz. The dramatic
upward shift in temporal encoding among summer fish was paralleled by
increases in best frequency (BF), maximum evoked spike rate at BF, VS
values at BF, and the percentage of units that showed significant VS to
iso-intensity tones >140 Hz. Reproductive summer females were best
suited to encode the higher harmonic components of male advertisement
calls. This first demonstration of a natural cyclicity in
peripheral auditory frequency sensitivity among vertebrates may
represent, in this case, an adaptive plasticity of the female
midshipman's auditory system to enhance the acquisition of auditory
information needed for mate identification and localization during the
breeding season.
Key words:
auditory plasticity; hearing; sacculus; reproduction; hair cell; vocalization
Copyright © 2003 Society for Neuroscience 0270-6474/03/2331049-10$05.00/0