Related Experiment Videos
Auditory nerve neurophonic produced by the frequency difference of two simultaneously presented tones
1Department of Psychology, University of California, Davis 95616-8686, USA. krhenry@ucdavis.edu
Hearing Research
|September 15, 1996
Summary
A difference tone (DT) response in gerbils originates from the auditory nerve, not the cochlea. This neural DT response is robust even at high frequencies and across varied stimulus conditions.
Area of Science:
- Auditory Neuroscience
- Otoacoustic Emissions
- Neurophysiology
Background:
- The auditory system generates complex responses to simultaneous sound stimuli.
- Difference tones (DTs) are psychoacoustic phenomena resulting from nonlinearities in the auditory system.
- The neural origin of DTs has been investigated using electrophysiological recordings.
Purpose of the Study:
- To investigate the neural origin of difference tone (DT) responses in the gerbil auditory system.
- To characterize the properties of the auditory nerve neurophonic (ANN) response to DTs.
- To determine the frequency range and robustness of DT-ANN generation.
Main Methods:
- Electrophysiological recordings from the cochlear round window (RW) in gerbils.
- Stimulation with phase-locked sinusoidal tones (F1 and F2) at various frequencies and polarities.
- Use of tetrodotoxin (TTX) to block axonal firing and isolate neural components.
- Analysis of time-averaged responses, including cochlear microphonic (CM) and auditory nerve neurophonic (ANN).
Main Results:
- A significant DT response (F2-F1) was observed in the RW electrical response.
- Tetrodotoxin (TTX) greatly attenuated the DT response, indicating a primary neural origin.
- Alternating tone polarity canceled cochlear microphonic (CM), isolating the auditory nerve neurophonic (ANN) response.
- A robust time-averaged DT-ANN was measured, even when individual tones were too high for phase-locking.
- The DT-ANN was largest for DTs between 700-1100 Hz and measurable up to F2 frequencies >30 kHz.
Conclusions:
- The difference tone (DT) response recorded at the gerbil cochlear round window is predominantly neural in origin, specifically from the auditory nerve.
- The auditory nerve neurophonic (ANN) response to DTs is robust and measurable across a wide range of stimulus frequencies and temporal/intensity variations.
- DT-ANN generation is efficient for specific difference frequencies (700-1100 Hz) and persists even at very high primary stimulus frequencies, suggesting complex neural processing.