Estimates of compression at low and high frequencies using masking additivity in normal and impaired ears.
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ABSTRACT:
SUBMITTER: Plack CJ
PROVIDER: S-EPMC2680663 | biostudies-other | 2008 Jun
REPOSITORIES: biostudies-other
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Project description:Cochlear hearing loss is often associated with a loss of basilar-membrane (BM) compression, which in turn may contribute to degraded processing of suprathreshold stimuli. Behavioral estimates of compression may therefore be useful as long as they are valid over a wide range of levels and frequencies. Additivity of forward masking (AFM) may provide such a measure, but research to date lacks normative data from normal-hearing (NH) listeners at high sound levels, which is necessary to evaluate data from hearing-impaired (HI) listeners. The present study measured AFM in six NH listeners for signal frequencies of 500, 1500, and 4000 Hz in the presence of background noise, designed to elevate signal thresholds to levels similar to those experienced by HI listeners. Results consistent with compressive BM responses were found for all six listeners at 500 Hz, five listeners at 1500 Hz, but only two listeners at 4000 Hz. Further measurements in the absence of background noise also indicated a lack of consistent compression at 4000 Hz at higher signal levels, in contrast to earlier results collected at lower levels. A better understanding of this issue will be required before AFM can be used as a general behavioral estimate of BM compression.
| S-EPMC3248057 | biostudies-other
Project description:ObjectivesThis study aimed to evaluate the informational component of speech-on-speech masking. Speech perception in the presence of a competing talker involves not only informational masking (IM) but also a number of masking processes involving interaction of masker and target energy in the auditory periphery. Such peripherally generated masking can be eliminated by presenting the target and masker in opposite ears (dichotically). However, this also reduces IM by providing listeners with lateralization cues that support spatial release from masking (SRM). In tonal sequences, IM can be isolated by rapidly switching the lateralization of dichotic target and masker streams across the ears, presumably producing ambiguous spatial percepts that interfere with SRM. However, it is not clear whether this technique works with speech materials.DesignSpeech reception thresholds (SRTs) were measured in 17 young normal-hearing adults for sentences produced by a female talker in the presence of a competing male talker under three different conditions: diotic (target and masker in both ears), dichotic, and dichotic but switching the target and masker streams across the ears. Because switching rate and signal coherence were expected to influence the amount of IM observed, these two factors varied across conditions. When switches occurred, they were either at word boundaries or periodically (every 116 msec) and either with or without a brief gap (84 msec) at every switch point. In addition, SRTs were measured in a quiet condition to rule out audibility as a limiting factor.ResultsSRTs were poorer for the four switching dichotic conditions than for the nonswitching dichotic condition, but better than for the diotic condition. Periodic switches without gaps resulted in the worst SRTs compared to the other switch conditions, thus maximizing IM.ConclusionsThese findings suggest that periodically switching the target and masker streams across the ears (without gaps) was the most efficient in disrupting SRM. Thus, this approach can be used in experiments that seek a relatively pure measure of IM, and could be readily extended to translational research.
| S-EPMC6856419 | biostudies-literature
Project description:Non-additive gene regulation has been recently suggested as an important factor promoting phenotypic variation and plasticity. In order to obtain a description of gene expression status at an early stage of ear development in a maize (Zea mays L.) F1 hybrid as relative to its parental inbreds, we compared gene expression profiles in immature ears of elite inbred lines B73 and H99 to one of their F1 hybrids (B73xH99) using cDNA microarray technology. Results show several genes expressed at a significantly different level between both inbred lines and their hybrid. In addition, gene expression non-additivity in the hybrid was detected on a broad scale, consisting of both dominance and over-dominance components, indicating that complex non-additive interactions at the molecular level exist in the developing ear of the studied maize hybrid. Non-additively regulated genes belong to a wide range of molecular functions, indicating that several regulatory and metabolic patterns are possibly affected during ear development in the investigated hybrid. We discuss the possibility that observed gene expression non-additivity in immature ear might be an early molecular manifestation of hybrid vigor, the most exploited factor for maize agronomic improvement.
2007-10-01 | GSE2771 | GEO
Project description:Experiment 1 examined comodulation masking release (CMR) for a 700-Hz tonal signal under conditions of N(o)S(o) (noise and signal interaurally in phase) and N(o)S(π) (noise in phase, signal out of phase) stimulation. The baseline stimulus for CMR was either a single 24-Hz wide narrowband noise centered on the signal frequency [on-signal band (OSB)] or the OSB plus, a set of flanking noise bands having random envelopes. Masking noise was either gated or continuous. The CMR, defined with respect to either the OSB or the random noise baseline, was smaller for N(o)S(π) than N(o)S(o) stimulation, particularly when the masker was continuous. Experiment 2 examined whether the same pattern of results would be obtained for a 2000-Hz signal frequency; the number of flanking bands was also manipulated (two versus eight). Results again showed smaller CMR for N(o)S(π) than N(o)S(o) stimulation for both continuous and gated masking noise. The CMR was larger with eight than with two flanking bands, and this difference was greater for N(o)S(o) than N(o)S(π). The results of this study are compatible with serial mechanisms of binaural and monaural masking release, but they indicate that the combined masking release (binaural masking-level difference and CMR) falls short of being additive.
| S-EPMC3087389 | biostudies-other
Project description:Non-additive gene regulation has been recently suggested as an important factor promoting phenotypic variation and plasticity. In order to obtain a description of gene expression status at an early stage of ear development in a maize (Zea mays L.) F1 hybrid as relative to its parental inbreds, we compared gene expression profiles in immature ears of elite inbred lines B73 and H99 to one of their F1 hybrids (B73xH99) using cDNA microarray technology. Results show several genes expressed at a significantly different level between both inbred lines and their hybrid. In addition, gene expression non-additivity in the hybrid was detected on a broad scale, consisting of both dominance and over-dominance components, indicating that complex non-additive interactions at the molecular level exist in the developing ear of the studied maize hybrid. Non-additively regulated genes belong to a wide range of molecular functions, indicating that several regulatory and metabolic patterns are possibly affected during ear development in the investigated hybrid. We discuss the possibility that observed gene expression non-additivity in immature ear might be an early molecular manifestation of hybrid vigor, the most exploited factor for maize agronomic improvement. We directly contrasted both B73 and H99 inbred lines vs. their F1 heterotic hybrid transcriptomes in immature ear. Our experimental design consisted of 10 cDNA microarray hybridizations, 5 for each combination of hybrid vs. inbred genotypes, involving 20 separate labeling reactions. Labeling dyes were swapped in two of the five replicates for each combination. In each hybridization, control channel was assigned to the F1 hybrid, and differences in transcriptional levels between B73 and H99 were inferred using the hybrid as a common reference sample in an indirect experimental design. To take in account variability in transcript population among individuals, total RNA coming from different isolations, each collected on multiple individuals, were mixed before poly(A+) RNA purification. All hybridizations on microarray slides were then performed using cDNA independently labeled from the poly(A+) RNA purification product for each genotype. Base-two logarithms of expression ratios were subjected to one-class response significance analysis in SAM v. 2.20 software [Tusher et al. 2001]. For each EST the estimates of additive parameter "a" and dominance parameter "d" (middle-parent heterosis) were obtained as a = (L2 – L1)/2 d = (L1 + L2)/2 (where L1 and L2 are mean base-two logarithms of expression ratios of F1 vs. B73 and F1 vs. H99, respectively). Positive values of "a" indicate expression values bigger in B73 than in H99. The dominance/additivity ratio (d/|a|) was also calculated [Falconer 1989]. Evaluation of statistical significance of parameters was done by calculating standard errors of the estimates "a" and "d" as standard errors of linear functions of the means. Significance testing was done correspondingly, using an F-test for linear contrasts. P-values for the families of tests corresponding to each parameter were subjected to global error analyses using a method based on fitting mixture distribution [Allison et al. 2002], allowing to estimate the false discovery rates (FDR) and false negative rates (FNR). Confidence intervals for d/|a| ratios were obtained by Fieller’s method [Piepho and Emrich 2005], allowing to classify the genes into different dominance type classes.
2007-10-01 | E-GEOD-2771 | biostudies-arrayexpress
Project description:Simultaneous, on-frequency masking is commonly assumed to be linear with increasing noise intensity. However, some evidence suggests that, expressed in terms of signal-to-noise ratio changes with background level changes, masking slopes can vary from 0 dB/dB. These results and evidence from a large sample of subjects with normal and impaired hearing demonstrate level-dependent changes in masking, large individual differences in masking among subjects with similar thresholds in quiet, and significant correlations of masking slope with other estimates of auditory function measured in the same backgrounds.
| S-EPMC3324301 | biostudies-other
Project description:ObjectivesTo determine whether suprathreshold measures of auditory function, such as distortion-product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs), are correlated with noise exposure history in normal-hearing human ears. Recent data from animal studies have revealed significant deafferentation of auditory nerve fibers after full recovery from temporary noise-induced hearing loss. Furthermore, these data report smaller ABR wave I amplitudes in noise-exposed animal ears when compared with non-noise-exposed control animals or prenoise exposure amplitudes in the same animal. It is unknown whether a similar phenomenon exists in the normal-hearing, noise-exposed human ear.DesignThirty normal-hearing human subjects with a range of noise exposure backgrounds (NEBs) participated in this study. NEB was quantified by the use of a noise exposure questionnaire that extensively queried loud sound exposure during the previous 12 months. DPOAEs were collected at three f2s (1, 2, and 4 kHz) over a range of L2s. DPOAE stimulus level began at 80 dB forward-pressure level and decreased in 10 dB steps. Two-channel ABRs were collected in response to click stimuli and 4 kHz tone bursts; one channel used an ipsilateral mastoid electrode and the other an ipsilateral tympanic membrane electrode. ABR stimulus level began at 90 dB nHL and was decreased in 10 dB steps. Amplitudes of waves I and V of the ABR were analyzed.ResultsA statistically significant relationship between ABR wave I amplitude and NEB was found for clicked-evoked ABRs recorded at a stimulus level of 90 dB nHL using a mastoid recording electrode. For this condition, ABR wave I amplitudes decreased as a function of NEB. Similar systematic trends were present for ABRs collected in response to clicks and 4 kHz tone bursts at additional suprathreshold stimulation levels (≥70 dB nHL). The relationship weakened and disappeared with decreases in stimulation level (≤60 dB nHL). Similar patterns were present for ABRs collected using a tympanic membrane electrode. However, these relationships were not statistically significant and were weaker and more variable than those collected using a mastoid electrode. In contrast to the findings for ABR wave I, wave V amplitude was not significantly related to NEB. Furthermore, there was no evidence of a systematic relationship between suprathreshold DPOAEs and NEB.ConclusionsA systematic trend of smaller ABR wave I amplitudes was found in normal-hearing human ears with greater amounts of voluntary NEB in response to suprathreshold clicks and 4 kHz tone bursts. These findings are consistent with the data from previous work completed in animals, where the reduction in suprathreshold responses was a result of deafferentation of high-threshold/low-spontaneous rate auditory nerve fibers. These data suggest that a similar mechanism might be operating in human ears after exposure to high sound levels. However, evidence of this damage is only apparent when examining suprathreshold wave I amplitude of the ABR. In contrast, suprathreshold DPOAE level was not significantly related to NEB. This was expected, given noise-induced auditory damage findings in animal ears did not extend to the outer hair cells, the generator for the DPOAE response.
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Project description:Hearing-impaired (HI) listeners often show less masking release (MR) than normal-hearing listeners when temporal fluctuations are imposed on a steady-state masker, even when accounting for overall audibility differences. This difference may be related to a loss of cochlear compression in HI listeners. Behavioral estimates of compression, using temporal masking curves (TMCs), were compared with MR for band-limited (500-4000 Hz) speech and pure tones in HI listeners and age-matched, noise-masked normal-hearing (NMNH) listeners. Compression and pure-tone MR estimates were made at 500, 1500, and 4000 Hz. The amount of MR was defined as the difference in performance between steady-state and 10-Hz square-wave-gated speech-shaped noise. In addition, temporal resolution was estimated from the slope of the off-frequency TMC. No significant relationship was found between estimated cochlear compression and MR for either speech or pure tones. NMNH listeners had significantly steeper off-frequency temporal masking recovery slopes than did HI listeners, and a small but significant correlation was observed between poorer temporal resolution and reduced MR for speech. The results suggest either that the effects of hearing impairment on MR are not determined primarily by changes in peripheral compression, or that the TMC does not provide a sufficiently reliable measure of cochlear compression.
| S-EPMC3799689 | biostudies-other
Project description:Hearing loss and auditory prostheses can alter auditory processing by inducing large pitch mismatches and broad pitch fusion between the two ears. Similar to integration of incongruent inputs in other sensory modalities, the mismatched, fused pitches are often averaged across ears for simple stimuli. Here, we measured parallel effects on complex stimulus integration using a new technique based on vowel classification in five bilateral hearing aid users and eight bimodal cochlear implant users. Continua between five pairs of synthetic vowels were created by varying the first formant spectral peak while keeping the second formant constant. Comparison of binaural and monaural vowel classification functions for each vowel pair continuum enabled visualization of the following frequency-dependent integration trends: (1) similar monaural and binaural functions, (2) ear dominance, (3) binaural averaging, and (4) binaural interference. Hearing aid users showed all trends, while bimodal cochlear implant users showed mostly ear dominance or interference. Interaural pitch mismatches, frequency ranges of binaural pitch fusion, and the relative weightings of pitch averaging across ears were also measured using tone and/or electrode stimulation. The presence of both large interaural pitch mismatches and broad pitch fusion was not sufficient to predict vowel integration trends such as binaural averaging or interference. The way that pitch averaging was weighted between ears also appears to be important for determining binaural vowel integration trends. Abnormally broad spectral fusion and the associated phoneme fusion across mismatched ears may underlie binaural speech perception interference observed in hearing aid and cochlear implant users.
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Project description:Sensory losses or reductions are frequently attributed to relaxed selection. However, anuran species have lost tympanic middle ears many times, despite anurans' use of acoustic communication and the benefit of middle ears for hearing airborne sound. Here we determine whether pre-existing alternative sensory pathways enable anurans lacking tympanic middle ears (termed earless anurans) to hear airborne sound as well as eared species or to better sense vibrations in the environment. We used auditory brainstem recordings to compare hearing and vibrational sensitivity among 10 species (six eared, four earless) within the Neotropical true toad family (Bufonidae). We found that species lacking middle ears are less sensitive to high-frequency sounds, however, low-frequency hearing and vibrational sensitivity are equivalent between eared and earless species. Furthermore, extratympanic hearing sensitivity varies among earless species, highlighting potential species differences in extratympanic hearing mechanisms. We argue that ancestral bufonids may have sufficient extratympanic hearing and vibrational sensitivity such that earless lineages tolerated the loss of high frequency hearing sensitivity by adopting species-specific behavioural strategies to detect conspecifics, predators and prey.
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