Polyphenols From Grape and Blueberry Improve Episodic Memory in Healthy Elderly with Lower Level of Memory Performance: A Bicentric Double-Blind, Randomized, Placebo-Controlled Clinical Study.

Polyphenols are promising nutritional bioactives exhibiting beneficial effect on age-related cognitive decline. This study evaluated the effect of a polyphenol-rich extract from grape and blueberry (PEGB) on memory of healthy elderly subjects (60-70 years-old). A bicentric, randomized, double-blind, placebo-controlled trial was conducted with 215 volunteers receiving 600 mg/day of PEGB (containing 258 mg flavonoids) or a placebo for 6 months. The primary outcome was the CANTAB Paired Associate Learning (PAL), a visuospatial learning and episodic memory test. Secondary outcomes included verbal episodic and recognition memory (VRM) and working memory (SSP). There was no significant effect of PEGB on the PAL on the whole cohort. Yet, PEGB supplementation improved VRM-free recall. Stratifying the cohort in quartiles based on PAL at baseline revealed a subgroup with advanced cognitive decline (decliners) who responded positively to the PEGB. In this group, PEGB consumption was also associated with a better VRM-delayed recognition. In addition to a lower polyphenol consumption, the urine metabolomic profile of decliners revealed that they excreted more metabolites. Urinary concentrations of specific flavan-3-ols metabolites were associated, at the end of the intervention, with the memory improvements. Our study demonstrates that PEGB improves age-related episodic memory decline in individuals with the highest cognitive impairments.

Cognitive Function Prediction of Performance During Dual-Tasks Across Adults With and Without Hearing Loss.

BACKGROUND: Dual-task procedures are commonly implemented to examine cognitive load and listening effort as individual differences in cognition often determine successful listening. However, which methods are most efficacious is unclear. Specifically, standardized, targeted assessment procedures for establishing cognitive function, and age-related changes that might account for changes in dual-task performance have yet to be established. Additional data are needed across aging populations, including middle-aged adults and older adults to establish the trend of performance changes throughout the aging process. Investigations of the relationship between cognitive function and dual-task performance may better inform clinical decisions. OBJECTIVE: The purpose of this study was to investigate if cognitive function predicts dual-task performance across adults with and without hearing loss. METHODS: Participants were divided into two groups based on age. Group 1: 14 listeners (Female = 11), 30-50 years old, with normal hearing. Group 2: 12 listeners (Female = 9), 60-80 years old, with normal hearing to near-normal hearing, including typical age-related hearing loss. Participants were administered four of the Woodcock-Johnson III cognitive subtests and standard hearing threshold procedures. All participants were tested in each of three experimental conditions, including two perceptual-cognitive dual-tasks: (1) Auditory word recognition + visual processing, (2) Auditory working memory (sentence) + visual processing in noise, and (3) Auditory working memory (word) + visual processing. RESULTS: Results indicated that cognitive function does predict dual-task performance regardless of age and hearing function. CONCLUSION: Cognitive function may predict dual-task performance during speech-in-noise tasks. Further research investigating the predictive value of related cognitive subtests to listening effort is warranted.

The impact of hearing aids and age-related hearing loss on auditory plasticity across three months - An electrical neuroimaging study.

The present study investigates behavioral and electrophysiological auditory and cognitive-related plasticity in three groups of healthy older adults (60-77 years). Group 1 was moderately hearing-impaired, experienced hearing aid users, and fitted with new hearing aids using non-linear frequency compression (NLFC on); Group 2, also moderately hearing-impaired, used the same type of hearing aids but NLFC was switched off during the entire period of study duration (NLFC off); Group 3 represented individuals with age-appropriate hearing (NHO) as controls, who were not different in IQ, gender, or age from Group 1 and 2. At five measurement time points (M1-M5) across three months, a series of active oddball tasks were administered while EEG was recorded. The stimuli comprised syllables consisting of naturally high-pitched fricatives (/sh/, /s/, and /f/), which are hard to distinguish for individuals with presbycusis. By applying a data-driven microstate approach to obtain global field power (GFP) as a measure of processing effort, the modulations of perceptual (P50, N1, P2) and cognitive-related (N2b, P3b) auditory evoked potentials were calculated and subsequently related to behavioral changes (accuracy and reaction time) across time. All groups improved their performance across time, but NHO showed consistently higher accuracy and faster reaction times than the hearing-impaired groups, especially under difficult conditions. Electrophysiological results complemented this finding by demonstrating longer latencies in the P50 and the N1 peak in hearing aid users. Furthermore, the GFP of cognitive-related evoked potentials decreased from M1 to M2 in the NHO group, while a comparable decrease in the hearing-impaired group was only evident at M5. After twelve weeks of hearing aid use of eight hours each day, we found a significantly lower GFP in the P3b of the group with NLFC on as compared to the group with NLFC off. These findings suggest higher processing effort, as evidenced by higher GFP, in hearing-impaired individuals when compared to those with normal hearing, although the hearing-impaired show a decrease of processing effort after repeated stimulus exposure. In addition, our findings indicate that the acclimatization to a new hearing aid algorithm may take several weeks.

Effect of age-related hearing loss on the click-rate-induced facilitation of acoustic reflex thresholds.

OBJECTIVE: This investigation was designed to evaluate the effect of age-related hearing loss on the click-rate-induced improvement in the acoustic reflex thresholds. DESIGN: Case-control study. STUDY SAMPLE: Data from five different adults ear-groups (15 ears each) were included in the study: 1. Younger with normal hearing. 2. Older with normal hearing. 3. Older with mild high-frequency loss. 4. Older with moderate high-frequency loss. 5. Older with low- and high-frequency loss. Ipsilateral acoustic reflex thresholds were obtained from the left and/or right ear/s by presenting clicks at the repetition rates of 50, 100, 150, 200 and 300 clicks/s. The rate-induced facilitation (RIF) was calculated by subtracting the lowest acoustic reflex threshold from the highest reflex threshold obtained across the various click-rates. RESULTS: The click-RIF is significantly reduced in older individuals compared to younger adults. There is no significant difference in RIF across the four older adult groups suggesting that an age-related, mild to moderate hearing loss has no significant effect on the click RIF of the acoustic reflex thresholds. CONCLUSIONS: Click-RIF may allow us to document the effect of ageing on temporal processing within the auditory brainstem area, in a time-efficient and objective manner using commercially available equipment.

Extension and evaluation of a near-end listening enhancement algorithm for listeners with normal and impaired hearing.

In many applications in which speech is played back via a sound reinforcement system such as public address systems and mobile phones, speech intelligibility is degraded by additive environmental noise. A possible solution to maintain high intelligibility in noise is to pre-process the speech signal based on the estimated noise power at the position of the listener. The previously proposed AdaptDRC algorithm [Schepker, Rennies, and Doclo (2015). J. Acoust. Soc. Am. 138, 2692-2706] applies both frequency shaping and dynamic range compression under an equal-power constraint, where the processing is adaptively controlled by short-term estimates of the speech intelligibility index. Previous evaluations of the algorithm have focused on normal-hearing listeners. In this study, the algorithm was extended with an adaptive gain stage under an equal-peak-power constraint, and evaluated with eleven normal-hearing and ten mildly to moderately hearing-impaired listeners. For normal-hearing listeners, average improvements in speech reception thresholds of about 4 and 8 dB compared to the unprocessed reference condition were measured for the original algorithm and its extension, respectively. For hearing-impaired listeners, the average improvements were about 2 and 6 dB, indicating that the relative improvement due to the proposed adaptive gain stage was larger for these listeners than the benefit of the original processing stages.

Hyperexcitability of inferior colliculus and acoustic startle reflex with age-related hearing loss.

Chronic tinnitus and hyperacusis often develop with age-related hearing loss presumably due to aberrant neural activity in the central auditory system (CAS) induced by cochlear pathologies. However, the full spectrum of physiological changes that occur in the CAS as a result age-related hearing loss are still poorly understood. To address this issue, neurophysiological measures were obtained from the cochlea and the inferior colliculus (IC) of 2, 6 and 12 month old C57BL/6J mice, a mouse model for early age-related hearing loss. Thresholds of the compound action potentials (CAP) in 6 and 12 month old mice were significantly higher than in 2 month old mice. The sound driven and spontaneous firing rates of IC neurons, recorded with 16 channel electrodes, revealed mean IC thresholds of 22.8 ± 6.5 dB (n = 167) at 2 months, 37.9 ± 6.2 dB (n = 132) at 6 months and 47.1 ± 15.3 dB (n = 151) at 12 months of age consistent with the rise in CAP thresholds. The characteristic frequencies (CF) of IC neurons ranged from 3 to 32 kHz in 2 month old mice; the upper CF ranged decreased to 26 kHz and 16 kHz in 6 and 12 month old mice respectively. The percentage of IC neurons with CFs between 8 and 12 kHz increased from 36.5% in 2 month old mice, to 48.8% and 76.2% in 6 and 12 month old mice, respectively, suggesting a downshift of IC CFs due to the high-frequency hearing loss. The average spontaneous firing rate (SFRs) of all recorded neurons in 2 month old mice was 3.2 ± 2.5 Hz (n = 167). For 6 and 12 month old mice, the SFRs of low CF neurons (<8 kHz) was maintained at 3-6 spikes/s; whereas SFRs of IC neurons with CFs > 8 kHz increased to 13.0 ± 15.4 (n = 68) Hz at 6 months of age and then declined to 4.8 ± 7.4 (n = 110) spikes/s at 12 months of age. In addition, sound-evoked activity at suprathreshold levels at 6 months of age was much higher than at 2 and 12 months of age. To evaluate the behavioral consequences of sound evoked hyperactivity in the IC, the amplitude of the acoustic startle reflex was measured at 4, 8 and 16 kHz using narrow band noise bursts. Acoustic startle reflex amplitudes in 6 and 12 month old mice (n = 4) were significantly larger than 2 month old mice (n = 4) at 4 and 8 kHz, but not 16 kHz. The enhanced reflex amplitudes suggest that high-intensity, low-frequency sounds are perceived as louder than normal in 6 and 12 month old mice compared to 2 month olds. The increased spontaneous activity, particularly at 6 months, may be related to tinnitus whereas the increase in sound-evoked activity and startle reflex amplitudes may be related to hyperacusis.

Speech based transmission index for all: An intelligibility metric for variable hearing ability.

A method to measure the speech intelligibility in public address systems for normal hearing and hearing impaired persons is presented. The proposed metric is an extension of the speech based Speech Transmission Index to account for accurate perceptual masking and variable hearing ability: The sound excitation pattern generated at the ear is accurately computed using an auditory filter model, and its shapes depend on frequency, sound level, and hearing impairment. This extension yields a better prediction of the intensity of auditory masking which is used to rectify the modulation transfer function and thus to objectively assess the speech intelligibility experienced by hearing impaired as well as by normal hearing persons in public spaces. The proposed metric was developed within the framework of the European Active and Assisted Living research program, and was labeled "SB-STI for All." Extensive subjective in-Lab and in vivo tests have been conducted and the proposed metric proved to have a good correlation with subjective intelligibility scores.

Association Between HbA1c Level and Hearing Impairment in a Nondiabetic Adult Population.

BACKGROUND: The aim of this study was to investigate whether glycosylated hemoglobin (HbA1c) level in nondiabetic patients is associated with hearing impairment in the general Korean population. PATIENTS AND METHODS: Data from the Korean National Health and Nutrition Examination Survey 2011-2013 were used in the analyses. Participants were excluded from this study for the following reasons: they could not provide data regarding pure tone audiometry, they had ear disease, they had brain disorders, asymmetric sensory neural hearing loss (HL), or they were younger than 40 years or had diabetes mellitus. Finally, 7449 participants were included in this study. RESULTS: The mean HbA1c levels in the low, middle, and high tertiles were 5.3% ± 0.2%, 5.7% ± 0.1%, and 6.1% ± 0.2%, respectively. The numbers of participants in the low, middle, and high tertiles were 2808, 2509, and 2132, respectively. The low-frequency, mid-frequency, high-frequency, and average hearing thresholds were significantly increased with increasing HbA1c tertile. Linear regression analyses showed that HbA1c level in the nondiabetic participants was associated with components of metabolic syndrome. The mean numbers of metabolic syndrome components in the low, middle, and high HbA1c tertiles were 1.22, 1.53, and 2.02, respectively. The participants in the middle and high HbA1c tertiles had a 1.239- and 1.253-fold increased risk of HL, respectively, compared with those in the low HbA1c tertile. CONCLUSION: HbA1c level was associated with hearing impairment in the nondiabetic participants of this study. Therefore, the participants with high HbA1c levels should be closely monitored for hearing impairment.

Sentence intelligibility during segmental interruption and masking by speech-modulated noise: Effects of age and hearing loss.

This study investigated how single-talker modulated noise impacts consonant and vowel cues to sentence intelligibility. Younger normal-hearing, older normal-hearing, and older hearing-impaired listeners completed speech recognition tests. All listeners received spectrally shaped speech matched to their individual audiometric thresholds to ensure sufficient audibility with the exception of a second younger listener group who received spectral shaping that matched the mean audiogram of the hearing-impaired listeners. Results demonstrated minimal declines in intelligibility for older listeners with normal hearing and more evident declines for older hearing-impaired listeners, possibly related to impaired temporal processing. A correlational analysis suggests a common underlying ability to process information during vowels that is predictive of speech-in-modulated noise abilities. Whereas, the ability to use consonant cues appears specific to the particular characteristics of the noise and interruption. Performance declines for older listeners were mostly confined to consonant conditions. Spectral shaping accounted for the primary contributions of audibility. However, comparison with the young spectral controls who received identical spectral shaping suggests that this procedure may reduce wideband temporal modulation cues due to frequency-specific amplification that affected high-frequency consonants more than low-frequency vowels. These spectral changes may impact speech intelligibility in certain modulation masking conditions.

Effects of age and hearing loss on the intelligibility of interrupted speech.

How age and hearing loss affect the perception of interrupted speech may vary based on both the physical properties of preserved or obliterated speech fragments and individual listener characteristics. To investigate perceptual processes and interruption parameters influencing intelligibility across interruption rates, participants of different age and hearing status heard sentences interrupted by silence at either a single primary rate (0.5-8 Hz; 25%, 50%, 75% duty cycle) or at an additional concurrent secondary rate (24 Hz; 50% duty cycle). Although age and hearing loss significantly affected intelligibility, the ability to integrate sub-phonemic speech fragments produced by the fast secondary rate was similar in all listener groups. Age and hearing loss interacted with rate with smallest group differences observed at the lowest and highest interruption rates of 0.5 and 24 Hz. Furthermore, intelligibility of dual-rate gated sentences was higher than single-rate gated sentences with the same proportion of retained speech. Correlations of intelligibility of interrupted speech to pure-tone thresholds, age, or measures of working memory and auditory spectro-temporal pattern discrimination were generally low-to-moderate and mostly nonsignificant. These findings demonstrate rate-dependent effects of age and hearing loss on the perception of interrupted speech, suggesting complex interactions of perceptual processes across different time scales.

Effects of age and hearing loss on recognition of unaccented and accented multisyllabic words.

The effects of age and hearing loss on recognition of unaccented and accented words of varying syllable length were investigated. It was hypothesized that with increments in length of syllables, there would be atypical alterations in syllable stress in accented compared to native English, and that these altered stress patterns would be sensitive to auditory temporal processing deficits with aging. Sets of one-, two-, three-, and four-syllable words with the same initial syllable were recorded by one native English and two Spanish-accented talkers. Lists of these words were presented in isolation and in sentence contexts to younger and older normal-hearing listeners and to older hearing-impaired listeners. Hearing loss effects were apparent for unaccented and accented monosyllabic words, whereas age effects were observed for recognition of accented multisyllabic words, consistent with the notion that altered syllable stress patterns with accent are sensitive for revealing effects of age. Older listeners also exhibited lower recognition scores for moderately accented words in sentence contexts than in isolation, suggesting that the added demands on working memory for words in sentence contexts impact recognition of accented speech. The general pattern of results suggests that hearing loss, age, and cognitive factors limit the ability to recognize Spanish-accented speech.

Age effects in discrimination of intervals within rhythmic tone sequences.

This study measured listener sensitivity to increments of a target inter-onset interval (IOI) embedded within tone sequences that featured different rhythmic patterns. The sequences consisted of six 50-ms 1000-Hz tone bursts separated by silent intervals that were adjusted to create different timing patterns. Control sequences were isochronous, with all tonal IOIs fixed at either 200 or 400 ms, while other patterns featured combinations of the two IOIs arranged to create different sequential tonal groupings. Duration difference limens in milliseconds for increments of a single sequence IOI were measured adaptively by adjusting the duration of an inter-tone silent interval. Specific target IOIs within sequences differed across discrimination conditions. Listeners included younger normal-hearing adults and groups of older adults with and without hearing loss. Discrimination performance measured for each of the older groups of listeners was observed to be equivalent, with each group exhibiting significantly poorer discrimination performance than the younger listeners in each sequence condition. Additionally, the specific influence of variable rhythmic grouping on temporal sensitivity was found to be greatest among older listeners.

Evaluation of serum antioxidants in age-related hearing loss.

BACKGROUND: Age-related hearing loss (ARHL) has been linked to the shift in the pro-oxidant/antioxidant ratio. Our objectives were to assess serum levels of retinol and zinc among the elderly individuals and to correlate the levels with hearing threshold. METHODS: Prospective study of apparently healthy individuals aged ≥60 years of age. Participants had complete clinical history, physical examination and pure tone average conducted. Blood samples were collected for determination of serum levels of retinol and zinc. Mann-Whitney U test was used to compare retinol and zinc values. Pearson's correlation test was used to determine the relationship between hearing threshold and serum levels of retinol and zinc. RESULTS: Among 126 elderly participants with mean age 67 ± 2.7 years; the mean pure tone average for air conduction was 29.3 ± 1.6 dBHL while the mean bone conduction was 36.5 ± 1.8 dBHL. The median values of serum retinol and zinc levels in the elderly participants who had hearing loss in the speech frequencies were 52 and 83.3 µg/L, respectively, while among participants with normal hearing threshold, values were 50 and 89.9 µg/L, respectively (p = 0.59 and 0.99, respectively). For the high frequencies, the median value of serum retinol and zinc levels among the elderly participants with normal hearing threshold was 70.3 and 99.9 µg/L, while among those with hearing loss, it was 46.9 and 83.2 µg/L, respectively (p = 0.000 and 0.005, respectively). CONCLUSION: Serum retinol and zinc levels were significantly lower among elderly with hearing loss involving the high frequencies. This is added evidence to extant literature on the possible role of antioxidants in the development of ARHL and suggests further study on the effect of antioxidants supplementation in the control of ARHL which is presently controversial and inconclusive.

The neurobiology of speech perception decline in aging.

Speech perception difficulties are common among elderlies; yet the underlying neural mechanisms are still poorly understood. New empirical evidence suggesting that brain senescence may be an important contributor to these difficulties has challenged the traditional view that peripheral hearing loss was the main factor in the etiology of these difficulties. Here, we investigated the relationship between structural and functional brain senescence and speech perception skills in aging. Following audiometric evaluations, participants underwent MRI while performing a speech perception task at different intelligibility levels. As expected, with age speech perception declined, even after controlling for hearing sensitivity using an audiological measure (pure tone averages), and a bioacoustical measure (DPOAEs recordings). Our results reveal that the core speech network, centered on the supratemporal cortex and ventral motor areas bilaterally, decreased in spatial extent in older adults. Importantly, our results also show that speech skills in aging are affected by changes in cortical thickness and in brain functioning. Age-independent intelligibility effects were found in several motor and premotor areas, including the left ventral premotor cortex and the right supplementary motor area (SMA). Age-dependent intelligibility effects were also found, mainly in sensorimotor cortical areas, and in the left dorsal anterior insula. In this region, changes in BOLD signal modulated the relationship between age and speech perception skills suggesting a role for this region in maintaining speech perception in older ages. These results provide important new insights into the neurobiology of speech perception in aging.

The role of stimulus complexity, spectral overlap, and pitch for gap-detection thresholds in young and old listeners.

Thresholds for detecting a gap between two complex tones were determined for young listeners with normal hearing and old listeners with mild age-related hearing loss. The leading tonal marker was always a 20-ms, 250-Hz complex tone with energy at 250, 500, 750, and 1000 Hz. The lagging marker, also tonal, could differ from the leading marker with respect to fundamental frequency (f0), the presence versus absence of energy at f0, and the degree to which it overlapped spectrally with the leading marker. All stimuli were presented with steeper (1 ms) and less steep (4 ms) envelope rise and fall times. F0 differences, decreases in the degree of spectral overlap between the markers, and shallower envelope shape all contributed to increases in gap-detection thresholds. Age differences for gap detection of complex sounds were generally small and constant when gap-detection thresholds were measured on a log scale. When comparing the results for complex sounds to thresholds obtained for pure-tones in a previous study by Heinrich and Schneider [(2006). J. Acoust. Soc. Am. 119, 2316-2326], thresholds increased in an orderly fashion from markers with identical (within-channel) pure tones to different (between-channel) pure tones to complex sounds. This pattern of results was true for listeners of both ages although younger listeners had smaller thresholds overall.

Effects of age and hearing loss on stream segregation based on interaural time differences.

The effect of interaural time differences (ITDs) on obligatory stream segregation for successive tone bursts was investigated for older listeners with normal hearing (ONH) and hearing loss (OHL), by measuring the threshold for detecting a rhythmic irregularity in an otherwise isochronous sequence of interleaved "A" and "B" tones. The A and B tones had equal but opposite ITDs from 0 to 0.5 ms. For some of the ONH listeners, the threshold increased with increasing ITD, but no OHL listener showed an effect of ITD. It is concluded that hearing loss reduces the potency of ITDs in inducing obligatory stream segregation.

Noise and age-related hearing loss: a study of 40 123 gold miners in South Africa.

OBJECTIVE AND DESIGN: This retrospective cohort study aimed to describe the differential effect of noise exposure and age-related hearing loss in a large sample of gold miners in South Africa. STUDY SAMPLE: Audiological data of 40 123 South African mine workers were investigated. Data of a non-noise-exposed control group (n = 6162) and group exposed to underground noise (≥ 85 dB A (TWA) (n = 33 961) were included. Within these two larger noise-exposed groups two homogenous exposure groups (HEG) were also selected for analyses, namely the driller group (n = 4399) and the administration group (administrative workers) (n = 2211). Participants were categorized in terms of noise exposure, age, and race. RESULTS: Significantly different thresholds (worse for underground noise group) with respect to the median for all frequencies after adjusting for age was evident between the noise-exposed and control groups (ANCOVA). The largest differences in hearing thresholds between the noise-exposed and control groups were observed at 3 and 4 kHz in the age group 36 to 45 years. Administration and driller group differed significantly (driller group worse results) with respect to the mean LFA512 and HFA346 after adjusting for age (ANCOVA). Black males had significantly better high-frequency hearing compared with white male counterparts but significantly worse low-frequency hearing. CONCLUSION: Age was the most important influence on hearing thresholds for the noise and control groups. Race was shown to be a very significant factor determining susceptibility to NIHL and ARHL.

Auditory and cognitive effects of aging on perception of environmental sounds in natural auditory scenes.

PURPOSE: Previously, Gygi and Shafiro (2011) found that when environmental sounds are semantically incongruent with the background scene (e.g., horse galloping in a restaurant), they can be identified more accurately by young normal-hearing listeners (YNH) than sounds congruent with the scene (e.g., horse galloping at a racetrack). This study investigated how age and high-frequency audibility affect this Incongruency Advantage (IA) effect. METHOD: In Experiments 1a and 1b, elderly listeners ( N = 18 for 1a; N = 10 for 1b) with age-appropriate hearing (EAH) were tested on target sounds and auditory scenes in 5 sound-to-scene ratios (So/Sc) between -3 and -18 dB. Experiment 2 tested 11 YNH on the same sound-scene pairings lowpass-filtered at 4 kHz (YNH-4k). RESULTS: The EAH and YNH-4k groups exhibited an almost identical pattern of significant IA effects, but both were at approximately 3.9 dB higher So/Sc than the previously tested YNH listeners. However, the psychometric functions revealed a shallower slope for EAH listeners compared with YNH listeners for the congruent stimuli only, suggesting a greater difficulty for the EAH listeners in attending to sounds expected to occur in a scene. CONCLUSIONS: These findings indicate that semantic relationships between environmental sounds in soundscapes are mediated by both audibility and cognitive factors and suggest a method for dissociating these factors.

Progressive hereditary hearing impairment caused by a MYO6 mutation resembles presbyacusis.

Since deafness is the most common sensorineural disorder in humans, better understanding of the underlying causes is necessary to improve counseling and rehabilitation. A Dutch family with autosomal dominantly inherited sensorineural hearing loss was clinically and genetically assessed. The MYO6 gene was selected to be sequenced because of similarities with other, previously described DFNA22 phenotypes and a pathogenic c.3610C > T (p.R1204W) mutation was found to co-segregate with the disease. This missense mutation results in a flat configured audiogram with a mild hearing loss, which becomes severe to profound and gently to steeply downsloping later in life. The age-related typical audiograms (ARTA) constructed for this family resemble presbyacusis. Speech audiometry and results of loudness scaling support the hypothesis that the phenotype of this specific MYO6 mutation mimics presbyacusis.

Age-related changes in the acoustic startle reflex in Fischer 344 and Long Evans rats.

The behavioral consequences of age-related changes in the auditory system were studied in Fischer 344 (F344) rats as a model of fast aging and in Long Evans (LE) rats as a model of normal aging. Hearing thresholds, the strength of the acoustic startle responses (ASRs) to noise and tonal stimuli, and the efficiency of the prepulse inhibition (PPI) of ASR were assessed in young-adult, middle-aged, and aged rats of both strains. Compared with LE rats, F344 rats showed larger age-related hearing threshold shifts, and the amplitudes of their startle responses were mostly lower. Both rat strains demonstrated a significant decrease of startle reactivity during aging. For tonal stimuli, this decrease occurred at an earlier age in the F344 rats: middle-aged F344 animals expressed similar startle reactivity as aged F344 animals, whereas middle-aged LE animals had similar startle reactivity as young-adult LE animals. For noise stimuli, on the other hand, a similar progression of age-related ASR changes was found in both strains. No significant relationship between the hearing thresholds and the ASR amplitudes was found within any age group. Auditory PPI was less efficient in F344 rats than in LE rats. An age-related reduction of the PPI of ASR was observed in rats of both strains; however, a significant reduction of PPI occurred only in aged rats. The results indicate that the ASR may serve as an indicator of central presbycusis.