Non-flat audiograms in sensorineural hearing loss and speech perception

Congenital olfactory impairment is linked to cortical changes in prefrontal and limbic brain regions

The human sense of smell is closely associated with morphological differences of the fronto-limbic system, specifically the piriform cortex and medial orbitofrontal cortex (mOFC). Still it is unclear whether cortical volume in the core olfactory areas and connected brain regions are shaped differently in individuals who suffer from lifelong olfactory deprivation relative to healthy normosmic individuals. To address this question, we examined if regional variations in gray matter volume were associated with smell ability in seventeen individuals with isolated congenital olfactory impairment (COI) matched with sixteen normosmic controls. All subjects underwent whole-brain magnetic resonance imaging, and voxel-based morphometry was used to estimate regional variations in grey matter volume. The analyses showed that relative to controls, COI subjects had significantly larger grey matter volumes in left middle frontal gyrus and right superior frontal sulcus (SFS). COI subjects with severe olfactory impairment (anosmia) had reduced grey matter volume in the left mOFC and increased volume in right piriform cortex and SFS. Within the COI group olfactory ability, measured with the "Sniffin' Sticks" test, was positively associated with larger grey matter volume in right posterior cingulate and parahippocampal cortices whereas the opposite relationship was observed in controls. Across COI subjects and controls, better olfactory detection threshold was associated with smaller volume in right piriform cortex, while olfactory identification was negatively associated with right SFS volume. Our findings suggest that lifelong olfactory deprivation trigger changes in the cortical volume of prefrontal and limbic brain regions previously linked to olfactory memory.

Effects of Various Extents of High-Frequency Hearing Loss on Speech Recognition and Gap Detection at Low Frequencies in Patients with Sensorineural Hearing Loss

This study explored whether the time-compressed speech perception varied with the degree of hearing loss in high-frequency sensorineural hearing loss (HF SNHL) individuals. 65 HF SNHL individuals with different cutoff frequencies were recruited and further divided into mildly, moderately, and/or severely affected subgroups in terms of the averaged thresholds of all frequencies exhibiting hearing loss. Time-compressed speech recognition scores under both quiet and noisy conditions and gap detection thresholds within low frequencies that had normal thresholds were obtained from all patients and compared with data from 11 age-matched individuals with normal hearing threshold at all frequencies. Correlations of the time-compressed speech recognition scores with the extents of HF SNHL and with the 1 kHz gap detection thresholds were studied across all participants. We found that the time-compressed speech recognition scores were significantly affected by and correlated with the extents of HF SNHL. The time-compressed speech recognition scores also correlated with the 1 kHz gap detection thresholds except when the compression ratio of speech was 0.8 under quiet condition. Above all, the extents of HF SNHL were significantly correlated with the 1 kHz gap thresholds.

[Decline of speech understanding in the hearing impaired elderly listeners who visited our hearing aid clinic]

The aim of this study was to investigate distinctive change in the hearing impaired elderly listeners, especially about speech recognition. Subjects were 525 patients (235 males, 290 females), from 60 to 98 years of age who had visited the Hearing Aid Clinic of Otorhinolaryngology, National Center for Geriatrics and Gerontology Hospital, between June 2001 and December 2012. Pure-tone air conduction threshold determination was administered to each subject. The speech audiometry materials used to define speech discrimination ability were Japanese monosyllabic word lists, 67S word lists. Sex- and age-specific trends in maximum discrimination score (MDS) and rollover index (RI) were shown in this study. RI was computed by the formula (PBmax-PBmin)/PBmax. PBmax has almost the same meaning as MDS in Japan. PBmin represented the lowest PB score above the test intensity level of PBmax. Mean MDSs were 80.8% in their sixties, 75.3% in their seventies, 60.7% in their eighties, and 45.5% in their nineties. The rate of decrease in mean MDS per decade accelerated in the older generation. Mean RIs were 0.18 in patients in their sixties, 0.24 in their seventies, 0.30 in their eighties, and 0.30 in their nineties. It increased until the age of eighties. In the model 1, multiple logistic analyses were performed to examine the effect of age (in 10-year increments), sex and mean hearing levels in pure tone average of values at 500, 1000, 2000, 4000 Hz (in 10 dB increments) on the MDS < 60%. Significant associations were observed between MDS < 60% and age (odds ratio, 3.03; 95% confidence interval, 2.38 to 3.85), and mean hearing levels in pure tone average of values at 500, 1000, 2000, 4000 Hz (2.33; 2.03 to 2.68). Sex was not associated with MDS < 60%. In the model 2, multiple logistic analyses adjusted for age and sex were performed to examine the effect of hearing level at test frequencies of 125, 250, 500, 1000, 2000, 4000, and 8000 Hz (in 10 dB increments)on the MDS < 60%. Significant associations were observed between MDS < 60% and hearing level at 250 Hz (2.04; 1.44 to 2.89), and 2000 Hz (1.46; 1.16 to 1.83), and 4000 Hz(1.24; 1.02 to 1.50). These outcomes suggest that the important point in qualifying the fitting of hearing aid is to present the list words at an adequate sound pressure level for evaluation of speech understanding especially in the hearing impaired elderly listeners.