Laser stimulation of auditory neurons: effect of shorter pulse duration and penetration depth.
We have pioneered what we believe is 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 microm) to stimulate auditory neurons of the gerbil. Radiant exposures measured at CAP threshold are similar for pulse durations of 5, 10, 30, and 100 micros, but greater for 300-micros-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 approximately 10 microm. The implications of these data could direct further research and design of an optical cochlear implant.
Izzo
Agnella D
AD
Department of Otolaryngology, Northwestern University, Chicago, Illinois 60611, USA. a-izzo@northwestern.edu
Walsh
Joseph T
JT
Ralph
Heather
H
Webb
Jim
J
Bendett
Mark
M
Wells
Jonathon
J
Richter
Claus-Peter
CP
D000200:Action Potentials / Q000502:physiology* / Q000528:radiation effects; D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005072:Evoked Potentials, Auditory / Q000502:physiology* / Q000528:radiation effects; D005849:Gerbillinae; D007834:Lasers; D009475:Neurons, Afferent / Q000502:physiology* / Q000528:radiation effects; D010775:Photic Stimulation / Q000379:methods*; D011829:Radiation Dosage; D013136:Spiral Ganglion / Q000502:physiology*