Masked auditory thresholds in three species of birds, as measured by the auditory brainstem response (L).
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ABSTRACT:
SUBMITTER: Noirot IC
PROVIDER: S-EPMC3135144 | biostudies-other | 2011 Jun
REPOSITORIES: biostudies-other
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Project description:This cross-sectional study had two goals: (1) Identify and quantify the effects of aging on the auditory brainstem response (ABR); (2) Describe how click rate and hearing impairment modify effects of aging. RESEARCH DESIGN AND ANALYSIS: ABR measures were obtained from 131 predominately male Veteran participants aged 26 to 71 yr. Metrics analyzed include amplitude and latency for waves I, III, and V, and the I-V interpeak latency interval (IPI) at three repetition rates (11, 51, and 71 clicks/sec) using both polarities. In order to avoid confounding from missing data due to hearing impairment, participants had hearing thresholds <40 dB HL at 2 kHz and 70 dB HL at 4 kHz in at least one ear. Additionally, the median 2, 3, and 4 kHz pure tone threshold average (PTA2,3,4) for the sample, ∼17 dB HL, was used to delineate subgroups of better and worse hearing ears, and only the better hearing sample was modeled statistically. We modeled ABR responses using age, repetition rate, and PTA2,3,4 as covariates. Random effects were used to model correlation between the two ears of a subject and across repetition rates. Inferences regarding effects of aging on ABR measures at each rate were derived from the fitted model. Results were compared to data from subjects with poorer hearing.Aging substantially diminished amplitudes of all of the principal ABR peaks, largely independent of any threshold differences within the group. For waves I and III, age-related amplitude decrements were greatest at a low (11/sec) click rate. At the 11/sec rate, the model-based mean wave III amplitude was significantly smaller in older compared with younger subjects even after adjusting for wave I amplitude. Aging also increased ABR peak latencies, with significant shifts limited to early waves. The I-V IPI did not change with age. For both younger and older subjects, increasing click presentation rate significantly decreased amplitudes of early peaks and prolonged latencies of later peaks, resulting in increased IPIs. Advanced age did not enhance effects of rate. Instead, the rate effect on wave I and III amplitudes was attenuated for the older subjects due to reduced peak amplitudes at lower click rates. Compared with model predictions from the sample of better hearing subjects, mean ABR amplitudes were diminished in the group with poorer hearing, and wave V latencies were prolonged.In a sample of veterans, aging substantially reduced amplitudes of all principal ABR peaks, with significant latency shifts limited to waves I and III. Aging did not influence the I-V IPI even at high click rates, suggesting that the observed absolute latency changes associated with aging can be attributed to changes in auditory nerve input. In contrast, ABR amplitude changes with age are not adequately explained by changes in wave I. Results suggest that aging reduces the numbers and/or synchrony of contributing auditory nerve units. Results also support the concept that aging reduces the numbers, though perhaps not the synchrony, of central ABR generators.
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Project description:Genome-wide gene expression was obtained in three auditory brainstem nuclei (defined below), at two different ages in mice, postnatal day (P)3 and P14. The primary aim was to identify genes which are differentially expressed between the medial nucleus of the trapezoid body (MNTB) and the superior olive (LSO), at both age groups. Tissue samples from the ventral cochlear nucleus (VCN), the medial nucleus of the trapezoid body (MNTB) and the lateral superior olive (LSO) were collected from 200 μm thick fresh transverse mouse brainstem slices prepared with a vibratome tissue slicer. Individual brainstem nuclei were dissected out with fine forceps under optical control with a binocular. For each nucleus (VCN, MNTB, and LSO), the tissue from six male C57Bl6 mice at postnatal day (P) 3, and from three male C57Bl6 mice at P14 was pooled. The RNA was isolated with the RNeasy Micro kit (Qiagen); RNA samples were amplified using a WT ovation Pico RNA amplification (Nugen, CA, USA). The cDNA was hybridized onto mouse Affymetrix microarrays 430 2.0 (Affymetrix, Santa Clara, USA).
2013-05-01 | E-GEOD-46500 | biostudies-arrayexpress
Project description:Genome-wide gene expression was obtained in three auditory brainstem nuclei (defined below), at two different ages in mice, postnatal day (P)3 and P14. The primary aim was to identify genes which are differentially expressed between the medial nucleus of the trapezoid body (MNTB) and the superior olive (LSO), at both age groups.
2013-05-01 | GSE46500 | GEO