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The speed of auditory low-side suppression
Marcel van der Heijden1, Philip X Joris
1Laboratory of Auditory, Neurophysiology, O. and N. Campus Gasthuisberg, Herestraat 49 - bus 801, B-3000 Leuven, Belgium. Marcel.vanderHeyden@med.kuleuven.ac.be
Journal of Neurophysiology
|September 3, 2004
Summary
Two-tone suppression in the auditory nerve is fast, but its precise timing varies with frequency. Lower frequencies show longer suppression delays than excitation delays, a difference that diminishes at higher frequencies.
Area of Science:
- Auditory Neuroscience
- Nonlinear Cochlear Mechanics
- Bioacoustics
Background:
- Two-tone suppression is a rapid nonlinear cochlear process.
- The precise timing of this auditory nerve response remains largely unquantified.
Purpose of the Study:
- To investigate the timing of low-side two-tone suppression in the auditory nerve.
- To quantify the temporal differences between excitation and suppression for auditory nerve fibers.
Main Methods:
- Utilized multitone complexes as auditory stimuli in anesthetized cats.
- Measured group delays of auditory nerve fiber responses with sub-millisecond accuracy.
- Compared delays of below-characteristic frequency (CF) tone complexes acting as exciters versus suppressors.
Main Results:
- For CFs below 10 kHz, suppression delays exceeded excitation delays by hundreds of microseconds.
- This temporal difference decreased as CF increased.
- The delay difference became negligible for CFs above 15 kHz.
Conclusions:
- Suppression timing is frequency-dependent, with lower CFs exhibiting longer delays.
- Results support a cochlear gain control mechanism for suppression.
- The integration time of this gain control is estimated to be around two cycles of the characteristic frequency.