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Laser stimulation of single auditory nerve fibers.

06:00 EDT 11th September 2010 | BioPortfolio

Summary of "Laser stimulation of single auditory nerve fibers."

OBJECTIVES/
HYPOTHESIS:
: One limitation with cochlear implants is the difficulty stimulating spatially discrete spiral ganglion cell groups because of electrode interactions. Multipolar electrodes have improved on this some, but also at the cost of much higher device power consumption. Recently, it has been shown that spatially selective stimulation of the auditory nerve is possible with a mid-infrared laser aimed at the spiral ganglion via the round window. However, these neurons must be driven at adequate rates for optical radiation to be useful in cochlear implants. We herein use single-fiber recordings to characterize the responses of auditory neurons to optical radiation. STUDY
DESIGN:
: In vivo study using normal-hearing adult gerbils.
METHODS:
: Two diode lasers were used for stimulation of the auditory nerve. They operated between 1.844 μm and 1.873 μm, with pulse durations of 35 μs to 1,000 μs, and at repetition rates up to 1,000 pulses per second (pps). The laser outputs were coupled to a 200-μm-diameter optical fiber placed against the round window membrane and oriented toward the spiral ganglion. The auditory nerve was exposed through a craniotomy, and recordings were taken from single fibers during acoustic and laser stimulation.
RESULTS:
: Action potentials occurred 2.5 ms to 4.0 ms after the laser pulse. The latency jitter was up to 3 ms. Maximum rates of discharge averaged 97 ± 52.5 action potentials per second. The neurons did not strictly respond to the laser at stimulation rates over 100 pps.
CONCLUSIONS:
: Auditory neurons can be stimulated by a laser beam passing through the round window membrane and driven at rates sufficient for useful auditory information. Optical stimulation and electrical stimulation have different characteristics; which could be selectively exploited in future cochlear implants. Laryngoscope, 2010.

Affiliation

Department of Surgery, ENT Section, Walter Reed Army Medical Center, Washington, DC.

Journal Details

This article was published in the following journal.

Name: The Laryngoscope
ISSN: 1531-4995
Pages:

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Medical and Biotech [MESH] Definitions

A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the unmyelinated nerve fibers are small. The axons to SCHWANN CELLS ratio is greater in the unmyelinated nerve fibers than that in the myelinated fiber (NERVE FIBERS, MYELINATED) which is 1:1. Usually several axons are surrounded by a single Schwann cell in the unmyelinated nerve fibers. Therefore, each unmyelinated fiber is not completely covered by the MYELIN SHEATH formed by the Schwann cell. Unmyelinated nerve fibers conduct impulses at low velocities. They represent the majority of peripheral sensory and autonomic fibers. They are also found in the spinal cord and brain.

A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.

The electric response evoked in the CEREBRAL CORTEX by ACOUSTIC STIMULATION or stimulation of the AUDITORY PATHWAYS.

The nerve husk. The outermost part of the MYELIN SHEATH covering a myelinated nerve fiber (NERVE FIBERS, MYELINATED) or a bundle of unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED).

Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the central nervous system.

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