Abstract:BackgroundRodent studies indicate that noise exposure can cause permanent damage to synapses between inner hair cells and high-threshold auditory nerve fibers, without permanently altering threshold sensitivity. These demonstrations of what is commonly known as hidden hearing loss have been confirmed in several rodent species, but the implications for human hearing are unclear.ObjectiveOur Medical Research Council–funded program aims to address this unanswered question, by investigating functional consequences… Show more
“…This article reports the first investigation of cumulative lifetime noise exposure on ascending auditory pathway function in audiometrically normal adults, as measured by the sustained and transient fMRI response and associated ABR in the same participants. Our primary hypothesis, informed by (Gu et al., 2010) and as pre-registered in Dewey et al. (2018a) was that higher lifetime noise exposure would lead to increased fMRI and ABR responses in central auditory regions compared to lower noise exposure, consistent with central gain enhancement (Gu et al., 2010, 2012; Auerbach et al., 2014) as a consequence of cochlear synaptopathy.…”
Section: Introductionmentioning
confidence: 83%
“…A protocol for this study has been published in (Dewey et al., 2018a), as recommended by The Organization for Human Brain Mapping (OHBM) Committee on Best Practice in Data Analysis and Sharing (COBIDAS; Nichols et al., 2017).…”
Section: Methodsmentioning
confidence: 99%
“…Participants aged 25–40 years, and with self-reported normal hearing, were recruited by advertisment across the University, social media and online message boards. A sample size of 60 participants was pre-defined to differentiate fMRI-related activity between noise exposure groups (n = 30 per group), with 80% power (Dewey et al., 2018a). Fig.…”
In animal models, exposure to high noise levels can cause permanent damage to hair-cell synapses (cochlear synaptopathy) for high-threshold auditory nerve fibers without affecting sensitivity to quiet sounds. This has been confirmed in several mammalian species, but the hypothesis that lifetime noise exposure affects auditory function in humans with normal audiometric thresholds remains unconfirmed and current evidence from human electrophysiology is contradictory. Here we report the auditory brainstem response (ABR), and both transient (stimulus onset and offset) and sustained functional magnetic resonance imaging (fMRI) responses throughout the human central auditory pathway across lifetime noise exposure. Healthy young individuals aged 25–40 years were recruited into high (n = 32) and low (n = 30) lifetime noise exposure groups, stratified for age, and balanced for audiometric threshold up to 16 kHz fMRI demonstrated robust broadband noise-related activity throughout the auditory pathway (cochlear nucleus, superior olivary complex, nucleus of the lateral lemniscus, inferior colliculus, medial geniculate body and auditory cortex). fMRI responses in the auditory pathway to broadband noise onset were significantly enhanced in the high noise exposure group relative to the low exposure group, differences in sustained fMRI responses did not reach significance, and no significant group differences were found in the click-evoked ABR. Exploratory analyses found no significant relationships between the neural responses and self-reported tinnitus or reduced sound-level tolerance (symptoms associated with synaptopathy). In summary, although a small effect, these fMRI results suggest that lifetime noise exposure may be associated with central hyperactivity in young adults with normal hearing thresholds.
“…This article reports the first investigation of cumulative lifetime noise exposure on ascending auditory pathway function in audiometrically normal adults, as measured by the sustained and transient fMRI response and associated ABR in the same participants. Our primary hypothesis, informed by (Gu et al., 2010) and as pre-registered in Dewey et al. (2018a) was that higher lifetime noise exposure would lead to increased fMRI and ABR responses in central auditory regions compared to lower noise exposure, consistent with central gain enhancement (Gu et al., 2010, 2012; Auerbach et al., 2014) as a consequence of cochlear synaptopathy.…”
Section: Introductionmentioning
confidence: 83%
“…A protocol for this study has been published in (Dewey et al., 2018a), as recommended by The Organization for Human Brain Mapping (OHBM) Committee on Best Practice in Data Analysis and Sharing (COBIDAS; Nichols et al., 2017).…”
Section: Methodsmentioning
confidence: 99%
“…Participants aged 25–40 years, and with self-reported normal hearing, were recruited by advertisment across the University, social media and online message boards. A sample size of 60 participants was pre-defined to differentiate fMRI-related activity between noise exposure groups (n = 30 per group), with 80% power (Dewey et al., 2018a). Fig.…”
In animal models, exposure to high noise levels can cause permanent damage to hair-cell synapses (cochlear synaptopathy) for high-threshold auditory nerve fibers without affecting sensitivity to quiet sounds. This has been confirmed in several mammalian species, but the hypothesis that lifetime noise exposure affects auditory function in humans with normal audiometric thresholds remains unconfirmed and current evidence from human electrophysiology is contradictory. Here we report the auditory brainstem response (ABR), and both transient (stimulus onset and offset) and sustained functional magnetic resonance imaging (fMRI) responses throughout the human central auditory pathway across lifetime noise exposure. Healthy young individuals aged 25–40 years were recruited into high (n = 32) and low (n = 30) lifetime noise exposure groups, stratified for age, and balanced for audiometric threshold up to 16 kHz fMRI demonstrated robust broadband noise-related activity throughout the auditory pathway (cochlear nucleus, superior olivary complex, nucleus of the lateral lemniscus, inferior colliculus, medial geniculate body and auditory cortex). fMRI responses in the auditory pathway to broadband noise onset were significantly enhanced in the high noise exposure group relative to the low exposure group, differences in sustained fMRI responses did not reach significance, and no significant group differences were found in the click-evoked ABR. Exploratory analyses found no significant relationships between the neural responses and self-reported tinnitus or reduced sound-level tolerance (symptoms associated with synaptopathy). In summary, although a small effect, these fMRI results suggest that lifetime noise exposure may be associated with central hyperactivity in young adults with normal hearing thresholds.
“… Figure 2. Noise exposure data from a cohort of 62 preliminary NESI respondents, obtained using a beta version of the NESI ( Dewey et al., 2018 ). Nineteen were classed as music-industry workers, the remaining 43 were not.…”
Lifetime noise exposure is generally quantified by self-report. The accuracy of
retrospective self-report is limited by respondent recall but is also bound to
be influenced by reporting procedures. Such procedures are of variable quality
in current measures of lifetime noise exposure, and off-the-shelf instruments
are not readily available. The Noise Exposure Structured Interview (NESI)
represents an attempt to draw together some of the stronger elements of existing
procedures and to provide solutions to their outstanding limitations. Reporting
is not restricted to prespecified exposure activities and instead encompasses
all activities that the respondent has experienced as noisy (defined based on
sound level estimated from vocal effort). Changing exposure habits over time are
reported by dividing the lifespan into discrete periods in which exposure habits
were approximately stable, with life milestones used to aid recall. Exposure
duration, sound level, and use of hearing protection are reported for each life
period separately. Simple-to-follow methods are provided for the estimation of
free-field sound level, the sound level emitted by personal listening devices,
and the attenuation provided by hearing protective equipment. An energy-based
means of combining the resulting data is supplied, along with a primarily
energy-based method for incorporating firearm-noise exposure. Finally, the NESI
acknowledges the need of some users to tailor the procedures; this flexibility
is afforded, and reasonable modifications are described. Competency needs of new
users are addressed through detailed interview instructions (including
troubleshooting tips) and a demonstration video. Limited evaluation data are
available, and future efforts at evaluation are proposed.
“…Cabe ressaltar que diversas mudanças na organização neuronal podem decorrer da exposição prolongada e danosa ao ruído, promovendo uma série de alterações no processamento sonoro, trazendo os referidos efeitos à tona, como a sensação de zumbido (Muca et al, 2018), ou, promovendo alterações centrais que desfavorecem as habilidades auditivas dos indivíduos expostos (Dewey, 2018).…”
Section: Efeitos Do Ruído Sobre a Saúde E Medidas De Proteçãounclassified
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