The common marmoset (Callithrix jacchus) as a model for research in age-related hearing loss

dc.contributor.advisorRatnam, Rama
dc.contributor.authorValero, Michelle Denise
dc.contributor.committeeMemberWilson, Charles
dc.contributor.committeeMemberWicha, Nicole
dc.contributor.committeeMemberTroyer, Todd
dc.contributor.committeeMemberMcFadden, Dennis
dc.contributor.committeeMemberTardif, Suzette
dc.descriptionThis item is available only to currently enrolled UTSA students, faculty or staff. To download, navigate to Log In in the top right-hand corner of this screen, then select Log in with my UTSA ID.
dc.description.abstractThis thesis describes the results from projects that investigated auditory function in the common marmoset (Callithrix jacchus) with the goal of developing this species as a model for studying human age-related hearing loss. The auditory brainstem response (ABR) was used to estimate hearing thresholds, and suprathreshold ABRs were measured to assess neural function. Distortion-product otoacoustic emissions (DPOAEs) were used to assess cochlear function. As the first to measure DPOAEs in marmosets, I first examined the reliability of DPOAE measurements in marmosets (Chapter 2) in different test/retest conditions. The general findings were in agreement with previous reports of reliability in DPOAEs measured from humans: reliability was best at high stimulus levels and lower frequencies, and refitting the probe tended to reduce the reliability of high-frequency DPOAEs. Furthermore, long-term repeatability was better in males than females. The poorest reliability was observed in the same-day condition that involved a 10-minute wait-period between test and retest (the short-term interval). I proposed that this poor reliability may have been due to the use of ketamine, an injectable anesthetic, which cannot be maintained at a constant circulating concentration throughout the procedure. I tested this by assessing reliability in a subset of the same marmosets under isoflurane, an inhalation anesthetic, which can be maintained at a constant level throughout the procedure (Chapter 3), and I found that repeatability in the short-term interval was improved under the isoflurane protocol, demonstrating one strength of isoflurane over ketamine anesthesia. Finally, ABRs and DPOAEs were measured in marmosets ranging from 1-12 years of age (Chapter 4). By comparing the individual ABR thresholds of marmosets older than 6 years of age, I demonstrated that marmosets exhibit variability in the age of onset, severity, and pattern of hearing loss. Subjects older than 6 years with high-frequency hearing loss exhibited changes in DPOAE levels and in waves I and II of the ABR, which represent peripheral and cochlear nucleus function, respectively. Central deficits such as increases in the wave I-V and II-V interpeak intervals were observed in older subjects regardless of their ABR thresholds. The results of Chapter 4 suggest that the common marmoset may be a valuable model system for research in presbycusis.
dc.description.departmentIntegrative Biology
dc.format.extent167 pages
dc.subjectAuditory Brainstem Response
dc.subjectDistortion-product otoacoustic emissions
dc.subjectNon-human primate
dc.titleThe common marmoset (Callithrix jacchus) as a model for research in age-related hearing loss
dcterms.accessRightspq_closed Biology of Texas at San Antonio of Philosophy


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