1 / 12

The Auditory Nervous System

The Auditory Nervous System. Classical Ascending Pathway. Review: Sensory Transduction. Basilar membrane, organ of Corti, & tectorial membrane Outer hair cells: “cochlear amplifiers” Displacement of stereocilia = depolarization Excitatory neurotransmitter released onto auditory nerve fibers.

noelle
Download Presentation

The Auditory Nervous System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Auditory Nervous System Classical Ascending Pathway

  2. Review: Sensory Transduction • Basilar membrane, organ of Corti, & tectorial membrane • Outer hair cells: “cochlear amplifiers” • Displacement of stereocilia = depolarization • Excitatory neurotransmitter released onto auditory nerve fibers

  3. Outline • Properties of auditory nerve fibers • Preservation of temporal and spatial coding throughout auditory ascending pathway • Focus on determination of azimuth via ITDs and ILDs in the superior olivary complex

  4. Auditory Nerve Fibers • Receptive fields: each fiber tuned to a specific frequency • Frequency Tuning Curves • Characteristic Frequency (CF): maximal sensitivity • All CFs cover entire audible frequency range

  5. Phase Locking • Auditory nerve fibers fire preferentially during particular phases of a waveform • Do not fire every time

  6. Two-Tone Suppression • One tone lowers response to a second tone • Excitatory response areas surrounded by suppressive response areas • Micromechanical properties of the cochlea: Outer hair cells • Broad frequency range of natural sounds • Gain Control to prevent saturation

  7. Ascending Pathway

  8. Overview of Functions • Cochlear nucleus: parallel processing begins • Superior Olivary Complex (SOC): sensitive to ITDs and ILDs (azimuth) • Inferior Colliculus: convergence of lower brain stem centers • ICC: direct input from cochlear nucleus combines with input from the SOC • Medial Geniculate & Auditory Cortex

  9. Superior Olivary Complex • Medial Superior Olive (MSO): ITDs • Delay lines & coincidence detectors • Composed of neurons with low CFs • Input from spherical bushy cells: primary-like • Low jitter

  10. Giant Synaptic Terminals: Endbulbs & Calyces • Endbulbs of Held in ventral cochlear nucleus • Hundreds of synapses • Calyceal endings in medial nucleus of the trapezoid body (MNTB)

  11. Superior Olivary Complex • Lateral Superior Olive (LSO): ILDs (“sound shadow”) • Ipsilateral = excitatory (spherical bushy cells) • Contralateral = inhibitory (globular bushy cells & synapses with calyceal endings in MNTB) • Composed of neurons with high CFs

  12. Summary • Auditory nerve fibers preserve spatial and temporal coding of sensory input • ITDs for low frequency sounds and ILDs for high frequency sounds are processed in parallel • Next, focus on integration of information in the higher brain centers

More Related