“…In summary, the number of PV-ir neurons increased with age in the CIC in the Long Evans strain, whereas in the with Long Evans rats, resulting in larger hearing threshold shifts, a decrease in the amplitude of click-evoked auditory brainstem responses, a diminution of distortion product otoacoustic emissions and a decrease in middle-ear compliance (Popelar et al 2003(Popelar et al , 2006. Age-related…”
Section: Discussionmentioning
confidence: 88%
“…In many tasks, a tone stimulus was used for fear conditioning (Oler and Markus, 1998;Villareal et al, 2004). Since old Fischer 344 rats are hearing-impaired with large hearing losses (Popelar et al, 2003(Popelar et al, , 2006Buckiova 2007), the results of those experiments may also have been influenced by the limited hearing abilities of the aged animals. The relationship ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T 16 between a decline in hippocampal PV-ir neuronal networks and cognitive deficits in the same strain may suggest that the large decline in the number of PV-ir neurons in the auditory cortex in Fischer 344 rats could contribute to the deterioration of hearing function in these animals.…”
To cite this version:Ladislav Ouda, Rastislav Druga, Josef Syka. Changes in parvalbumin immunoreactivity with aging in the central auditory system of the rat. Experimental Gerontology, Elsevier, 2008, 43 (8)
“…In summary, the number of PV-ir neurons increased with age in the CIC in the Long Evans strain, whereas in the with Long Evans rats, resulting in larger hearing threshold shifts, a decrease in the amplitude of click-evoked auditory brainstem responses, a diminution of distortion product otoacoustic emissions and a decrease in middle-ear compliance (Popelar et al 2003(Popelar et al , 2006. Age-related…”
Section: Discussionmentioning
confidence: 88%
“…In many tasks, a tone stimulus was used for fear conditioning (Oler and Markus, 1998;Villareal et al, 2004). Since old Fischer 344 rats are hearing-impaired with large hearing losses (Popelar et al, 2003(Popelar et al, , 2006Buckiova 2007), the results of those experiments may also have been influenced by the limited hearing abilities of the aged animals. The relationship ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T 16 between a decline in hippocampal PV-ir neuronal networks and cognitive deficits in the same strain may suggest that the large decline in the number of PV-ir neurons in the auditory cortex in Fischer 344 rats could contribute to the deterioration of hearing function in these animals.…”
To cite this version:Ladislav Ouda, Rastislav Druga, Josef Syka. Changes in parvalbumin immunoreactivity with aging in the central auditory system of the rat. Experimental Gerontology, Elsevier, 2008, 43 (8)
“…At the repetition rate of 26.6 Hz, there are no differential age-related decrements in ABR amplitudes (Burkard and Sims 2001). The 0.1-ms click duration was chosen to be consistent with other animal and human studies (Rowe 1978;Sand 1991;Backoff and Caspary 1994;Popelar et al 2006;Parthasarathy et al 2010). Though the exact spectral content of the 0.1-ms clicks and sAM noise are different, both are broadband stimuli, and the correlations observed likely measure the relationship between the phasic synchrony of the ABRs and the sustained temporal processing of the EFRs.…”
Hearing thresholds and wave amplitudes measured using auditory brainstem responses (ABRs) to brief sounds are the predominantly used clinical measures to objectively assess auditory function. However, frequency-following responses (FFRs) to tonal carriers and to the modulation envelope (envelope-following responses or EFRs) to longer and spectro-temporally modulated stimuli are rapidly gaining prominence as a measure of complex sound processing in the brainstem and midbrain. In spite of numerous studies reporting changes in hearing thresholds, ABR wave amplitudes, and the FFRs and EFRs under neurodegenerative conditions, including aging, the relationships between these metrics are not clearly understood. In this study, the relationships between ABR thresholds, ABR wave amplitudes, and EFRs are explored in a rodent model of aging. ABRs to broadband click stimuli and EFRs to sinusoidally amplitude-modulated noise carriers were measured in young (3-6 months) and aged (22-25 months) Fischer-344 rats. ABR thresholds and amplitudes of the different waves as well as phase-locking amplitudes of EFRs were calculated. Age-related differences were observed in all these measures, primarily as increases in ABR thresholds and decreases in ABR wave amplitudes and EFR phaselocking capacity. There were no observed correlations between the ABR thresholds and the ABR wave amplitudes. Significant correlations between the EFR amplitudes and ABR wave amplitudes were observed across a range of modulation frequencies in the young. However, no such significant correlations were found in the aged. The aged click ABR amplitudes were found to be lower than would be predicted using a linear regression model of the young, suggesting altered gain mechanisms in the relationship between ABRs and FFRs with age. These results suggest that ABR thresholds, ABR wave amplitudes, and EFRs measure complementary aspects of overlapping neurophysiological processes and the relationships between these measurements changes asymmetrically with age. Hence, measuring all three metrics provides a more complete assessment of auditory function, especially under pathological conditions like aging.
“…Peak pressure provides a measure of the pressure in the middle ear space. Middle ear infections often manifest with negative middle ear pressures, as seen in Popelar et al (2006). Compliance provides an index of the tympanic membranes mobility.…”
Studies of the F344 rat have shown a variety of age-related auditory anatomy and physiology changes. The current study was undertaken to clarify the ARHL in the F344 rat, by examining the auditory pathway of the F344/NHsd substrain that is distributed by Harlan Laboratories for research in the United States. The F344/NHsd rat begins to lose its hearing at about 12 months, and by 24 months, there are 50-60 dB auditory brainstem response threshold shifts at 20 and 40 kHz and 20 dB losses at 5-10 kHz. Distortion product otoacoustic emissions (DPOAE) amplitudes at 1.8 to 12 kHz stimuli were depressed in the older (18-24 months) rats. Amplitude input-output functions of the compound action potential (CAP) were also depressed across frequency. The endocochlear potential (EP) was 90-100 mV in the 3 month old rats. All but one of the 24 month old rats' EPs were in the +75-85 mV range. Tympanometry revealed no differences in middle ear function between the young and older rats. Collectively, these findings suggest damage to the outer hair cells, but anatomical examination of the outer hair cells revealed a relative lack of cell loss compared to the magnitude of the hearing and DPOAE loss.
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