Effects of chronic high-rate electrical stimulation on the cochlea and eighth nerve in the deafened guinea pig.
This study was undertaken to examine the effects of chronic high-rate stimulation on the eighth nerve and cochlea. Fifty-four male pigmented guinea pigs were deafened and implanted with single ball electrodes in scala tympani. Four groups of animals received chronic electrical stimulation at a level of 5 microCol/cm2/ph for 1000 h as follows: Group A: 1000 Hz, 100 microseconds/ph duration, 100 microA peak; Group B: 250 Hz, 100 microseconds/ph duration, 100 microA peak; Group C: 2750 Hz, 36 microseconds/ph duration, 250 microA peak; Group D: 250 Hz, 400 microseconds/ph duration, 25 microA peak. Also, two control groups received 20 min stimulation during weekly electrically evoked auditory brainstem response (eABR) measurement (Group E) and about 5 s stimulation (Group F) during a brief eABR 3 day postimplantation and at perfusion. On Day 50, animals were perfused, midmodiolar sections cut and a quantitative assessment of spiral ganglion cells (SGC) performed. All stimulated subjects showed a similar decrease in eABR thresholds and dynamic range over time. No stimulation conditions induced pathology. All stimulation conditions enhanced survival of SGCs compared to unimplanted ears and implanted non-stimulated ears (Group F). There were no statistically significant differences in SGC survival between any stimulated groups, including Group E stimulated once a week. In conclusion, high-rate stimulation, under the conditions of this study, provides no additional risks and the same benefits to SGC survival as low-rate stimulation.
Mitchell
A
A
Kresge Hearing Research Institute, University of Michigan, Ann Arbor 48109-0506, USA.
Miller
J M
JM
Finger
P A
PA
Heller
J W
JW
Raphael
Y
Y
Altschuler
R A
RA
D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D003051:Cochlea / Q000294:innervation / Q000502:physiology*; D003054:Cochlear Implants / Q000592:standards; D003638:Deafness / Q000139:chemically induced / Q000503:physiopathology* / Q000601:surgery; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004594:Electrophysiology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000166:cytology / Q000473:pathology; D018072:Hair Cells, Auditory, Outer / Q000166:cytology / Q000473:pathology; D008297:Male; D012533:Scala Tympani / Q000502:physiology; D013136:Spiral Ganglion / Q000166:cytology / Q000473:pathology / Q000502:physiology; D013680:Tectorial Membrane / Q000473:pathology; D000159:Vestibulocochlear Nerve / Q000502:physiology*