Laser stimulation of auditory neurons: effect of shorter pulse duration and penetration depth
Agnella D Izzo 1*, Joseph T Walsh 2, Heather Ralph 3, Jim Webb 3, Mark Bendett 3, Jonathon Wells 3 and Claus-Peter Richter 1
1 Otolaryngology, Northwestern University
2 Biomedical Engineering, Northwestern University
3 Aculight Corporation
* To whom correspondence should be addressed. E-mail: a-izzo{at}northwestern.edu.
Submitted on July 11, 2007
Revised on August 17, 2007
Accepted on 31 October 2007
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Abstract |
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We have pioneered a novel method of stimulating cochlear neurons, using pulsed infrared radiation, based on the hypothesis that optical radiation can provide more spatially selective stimulation of the cochlea than electric current. Very little of the available optical parameter space has been used for optical stimulation of neurons. Here, we use a pulsed diode laser (1.94 µm) to stimulate auditory neurons of the gerbil. Radiant exposures measured at CAP threshold are similar for pulse durations of 5, 10, 30, and 100 µs, but greater for 300-µs-long pulses. There is evidence that water absorption of optical radiation is a significant factor in optical stimulation. Heat-transfer-based analysis of the data indicates that potential structures involved in optical stimulation of cochlear neurons have a dimension on the order of ~5 µm. The implications of these data could direct further research and design of an optical cochlear implant.
Key Words:
cochlear implant, optical stimulation, selectivity, spiral ganglion cell
