title: Type II Cochlear Ganglion Neurons Do Not Drive the Olivocochlear Reflex: Re-Examination of the Cochlear Phenotype in Peripherin Knock-Out Mice.
abstract: The cochlear nerve includes a small population of unmyelinated sensory fibers connecting outer hair cells to the brain. The functional role of these type II afferent neurons is controversial, because neurophysiological data are sparse. A recent study (Froud et al., 2015) reported that targeted deletion of peripherin, a type of neurofilament, eliminated type II afferents and inactivated efferent feedback to the outer hair cells, thereby suggesting that type II afferents were the sensory drive to this sound-evoked, negative-feedback reflex, the olivocochlear pathway. Here, we re-evaluated the cochlear phenotype in mice from the peripherin knock-out line and show that (1) type II afferent terminals are present in normal number and (2) olivocochlear suppression of cochlear responses is absent even when this efferent pathway is directly activated by shocks. We conclude that type II neurons are not the sensory drive for the efferent reflex and that peripherin deletion likely causes dysfunction of synaptic transmission between olivocochlear terminals and their peripheral targets.
authors: Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts 02115; Eaton-Peabody Laboratories, Massachusetts Eye & Ear Infirmary, Boston, Massachusetts 02114-3096.
authors: Stéphane
authors: 0000-0003-2813-6439
authors: S
authors: Maison
authors: Eaton-Peabody Laboratories, Massachusetts Eye & Ear Infirmary , Boston, Massachusetts 02114-3096.
authors: Leslie D
authors: 0000-0002-1973-1730
authors: LD
authors: Liberman
authors: Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts 02115; Eaton-Peabody Laboratories, Massachusetts Eye & Ear Infirmary, Boston, Massachusetts 02114-3096.
authors: M Charles
authors: 0000-0002-1973-1730
authors: MC
authors: Liberman
mesh_terms: D000818:Animals; D003051:Cochlea / Q000378:metabolism* / Q000473:pathology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D056228:Feedback, Sensory / Q000502:physiology; D018345:Mice, Knockout; D009434:Neural Pathways / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D009847:Olivary Nucleus / Q000378:metabolism* / Q000473:pathology; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology; D064531:Peripherins / Q000172:deficiency* / Q000235:genetics; D012018:Reflex / Q000502:physiology*
chemical_list: D064531:Peripherins; C579005:Prph protein, mouse
keywords: cochlea; feedback; hair cells; olivocochlear reflex; peripherin