Related Experiment Video
Updated: Jun 27, 2026
09:54
Morphological and Functional Evaluation of Ribbon Synapses at Specific Frequency Regions of the Mouse Cochlea
Published on: May 10, 2019
Sensitive response to low-frequency cochlear distortion products in the auditory midbrain
Cornelius Abel1, Manfred Kössl
1Institut für Zellbiologie und Neurowissenschaft, Siesmayerstrasse 70A, Goethe-Universität, Frankfurt/M., Germany. abel@bio.uni-frankfurt.de
Journal of Neurophysiology
|November 28, 2008
Summary
Distortion product otoacoustic emissions (DPOAEs) reflect inner ear activity. This study found that neural responses to distortion products (DPs) in the brainstem can exceed DPOAE levels, especially at low frequencies, suggesting significant intracochlear DP generation.
Area of Science:
- Auditory Neuroscience
- Cochlear Physiology
- Neuroethology
Background:
- Nonlinear cochlear amplification generates distortion products (DPs) during auditory stimulation.
- DP energy can be reemitted as distortion product otoacoustic emissions (DPOAEs) and also elicit neural responses.
- Understanding the relationship between intracochlear DPs and measurable DPOAEs is crucial for interpreting auditory processing.
Purpose of the Study:
- To investigate the relationship between simultaneously measured DPOAEs and neural responses to DPs in the inferior colliculus (IC).
- To determine if intracochlear DP levels correlate with DPOAE levels across different frequencies.
- To explore the role of intracochlear DPs in encoding pitch information from complex sounds.
Main Methods:
- Recorded inferior colliculus (IC) neuronal responses in gerbils during two-tone stimulation.
- Measured distortion product otoacoustic emissions (DPOAEs) concurrently with neuronal activity.
- Used phase-adjusted tone stimuli to verify neuronal responses to intracochlear distortion products (f2-f1 and 2f1-f2).
Main Results:
- Neuronal responses to DPs above 1.3 kHz correlated well with measured DPOAEs.
- Below 1.3 kHz, neural responses indicated significantly higher intracochlear DP levels than DPOAE levels.
- In some low-frequency neurons, DP responses occurred even below the neuron's characteristic frequency (CF) threshold.
Conclusions:
- Discrepancies between intracochlear DP levels and DPOAEs at low frequencies suggest reduced middle ear gain affects DPOAE measurement.
- High intracochlear DP levels contribute to pitch perception of complex auditory stimuli.
- Neuronal processing of distortion products may not always be directly reflected by external DPOAE measurements.
Related Concept Videos
01:13The Cochlea
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
01:15Auditory Pathway
Auditory pathways constitute the complex neural circuits responsible for transmitting and interpreting auditory information from the peripheral auditory system to the brain. Sound waves are initially captured by the outer ear, funneled through the ear canal, and reach the tympanic membrane (eardrum). These vibrations are transmitted via the middle ear's ossicles to the inner ear's cochlea.
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
01:31Hearing
When we hear a sound, our nervous system is detecting sound waves—pressure waves of mechanical energy traveling through a medium. The frequency of the wave is perceived as pitch, while the amplitude is perceived as loudness.
01:22Hair Cells
Hair cells are the sensory receptors of the auditory system—they transduce mechanical sound waves into electrical energy that the nervous system can understand. Hair cells are located in the organ of Corti within the cochlea of the inner ear, between the basilar and tectorial membranes. The actual sensory receptors are called inner hair cells. The outer hair cells serve other functions, such as sound amplification in the cochlea, and are not discussed in detail here.
01:16Anatomy of the Ear
Auditory sensation, commonly called hearing, involves the transformation of sonic waves into neural impulses facilitated by the structures of the auditory organ. The prominent, flesh-like structure on the side of the head, called the auricle, directs sound waves towards the auditory canal. The auricle is often mislabeled as the pinna, a term more aligned with mobile structures like a feline's external ear. The auditory canal penetrates the cranium via the external auditory meatus of the...
01:21Perceiving Loudness, Pitch, and Location
The human brain perceives pitch through two primary mechanisms reflected in place theory and frequency theory. Each mechanism describes how sound waves are interpreted as specific pitches by the brain, offering insights into the intricate processes of auditory perception.
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by identifying...
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by identifying...