Dynamical mechanisms of neural firing irregularity and modulation sensitivity with applications to cochlear implants

The degree of irregularity apparent in the discharge patterns of electrically stimulated auditory-nerve fibers depends upon the stimulation rate. Whereas fibers fire regularly at low stimulation rates, the same fibers fire irregularly at high rates. The irregularity observed at high stimulation rates has been attributed to noise caused by the random open and closing of voltage-gated ion channels. This explanation however is incomplete: an additional mechanism must be operating to account for the different effects of noise at the two stimulation rates. We have identified such an additional rate-dependent mechanism. Specifically, we show in the Fitzhugh-Nagumo (FN) model that the stability to perturbations such as noise depends upon the stimulation rate. At sufficiently high rates a dynamical instability arises that accounts for the main statistical features of the irregular discharge pattern, even in the absence of ongoing physiological noise. In addition, we show that this instability accounts for both the statistical independence exhibited by different fibers in the stimulated population and their sensitivity to amplitude modulations applied to an ongoing stimulus.

Department dc:contributor.department

Harvard University--MIT Division of Health Sciences and Technology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• O'Gorman, David E

Advisor dc:contributor.advisor

• Christopher A. Shera and John A. White.

• Harvard University--MIT Division of Health Sciences and Technology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/35513
• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Identifier URI

http://dspace.mit.edu/handle/1721.1/35513

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/35513