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Cochlea – 2; Auditory nerve. Dr. Duck O. Kim. Salamanca, Spain May, 2010. Purves, Fig 12-8; adapted from Lewis & Hudspeth, 1983. innervation of IHCs and OHCs by cochlear ganglion neurons. adapted from Spoendlin, 1972. frequency tuning curves of single cochlear nerve fibers.
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Cochlea – 2; Auditory nerve Dr. Duck O. Kim Salamanca, Spain May, 2010
Purves, Fig 12-8; adapted from Lewis & Hudspeth, 1983
innervation of IHCs and OHCs by cochlear ganglion neurons adapted from Spoendlin, 1972
frequency tuning curves of single cochlear nerve fibers (1972) level (dB SPL) 0.1 1 10 40 frequency (kHz)
Auditory nerve fibers exhibit phase locking for low stimulus frequencies (< a few kilohertz). stimulus: 300 Hz pure tone Evans, 1975
Inter-spike interval histogram Number of observations Rose, 1967; Yost Fig 9-8
Phase locking of auditory nerve fibers lead to neural coding of inter-aural time difference (ITD), a cue for sound location. Phase locking may also contribute to coding of sound frequency.
two codes of frequency in auditory nerve fibers val
Thresholds of low & medium spontaneous- rate auditory nerve fibers are higher. Liberman, 1978; Yost, Fig 9-1
population responses of low-SR auditory nerve fibers discharge rate (spikes/s) increase of sound intensity -> (1) increase of discharge rates of auditory nerve fibers (with low spontaneous rates); (2) increase of number of excited auditory nerve fibers Kim et al., 1991 distance along cochlea
olivocochlear neurons LOC: lateral olivocochlear MOC: medial olivocochlear Warr et al., 2002
hearing loss examples_____ conductive hearing loss otosclerosis otitis media impaction of ear canal sensorineural hearing loss acoustic trauma ototoxic drugs Meniere’s disease mixed hearing loss presbycusis