Exploring the Influence of Extended High-Frequency Hearing on Cochlear Functioning at Lower Frequencies.

PURPOSE: Diminished basal cochlear function, as indicated by elevated hearing thresholds in the extended high frequencies (EHFs), has been associated with lower levels of click-evoked and distortion-product otoacoustic emissions measured at lower frequencies. However, stimulus-frequency otoacoustic emissions (SFOAEs) at low-probe levels are reflection-source emissions that do not share the same generation mechanism as distortion-source emissions. The primary objective of the present study was to examine the influence of hearing thresholds in the EHFs on SFOAEs measured at lower frequencies. METHOD: SFOAEs were recorded from both ears in 45 individuals with normal hearing thresholds in the conventional audiometric frequencies (0.25-8 kHz). Hearing thresholds were also measured at EHFs (10, 12.5, and 16 kHz). SFOAE magnitudes and signal-to-noise ratios (SNRs) were averaged across 1, 2, and 4 kHz probe frequencies and also averaged for high-probe frequencies (2 and 4 kHz). RESULTS: SFOAE magnitudes and SNRs were significantly higher for ears with better EHF hearing relative to poorer EHF hearing, categorized based on the median split. In addition, hearing in the EHFs significantly contributed to the variance in all SFOAE measures, except for the high-frequency SFOAE magnitudes model. However, hearing thresholds at the probe frequencies did not significantly contribute to the variance in SFOAEs. CONCLUSIONS: The study findings suggest that alterations in the basal cochlea, as revealed by EHF hearing thresholds, could be associated with diminished cochlear functioning in relatively apical regions, shown by SFOAEs at lower frequencies, in individuals with normal audiograms. These findings underscore the significance of considering EHF thresholds in audiological evaluations, as alterations in these frequencies may reflect broader cochlear health status.

Explainable machine learning reveals the relationship between hearing thresholds and speech-in-noise recognition in listeners with normal audiograms.

Some individuals complain of listening-in-noise difficulty despite having a normal audiogram. In this study, machine learning is applied to examine the extent to which hearing thresholds can predict speech-in-noise recognition among normal-hearing individuals. The specific goals were to (1) compare the performance of one standard (GAM, generalized additive model) and four machine learning models (ANN, artificial neural network; DNN, deep neural network; RF, random forest; XGBoost; eXtreme gradient boosting), and (2) examine the relative contribution of individual audiometric frequencies and demographic variables in predicting speech-in-noise recognition. Archival data included thresholds (0.25-16 kHz) and speech recognition thresholds (SRTs) from listeners with clinically normal audiograms (n = 764 participants or 1528 ears; age, 4-38 years old). Among the machine learning models, XGBoost performed significantly better than other methods (mean absolute error; MAE = 1.62 dB). ANN and RF yielded similar performances (MAE = 1.68 and 1.67 dB, respectively), whereas, surprisingly, DNN showed relatively poorer performance (MAE = 1.94 dB). The MAE for GAM was 1.61 dB. SHapley Additive exPlanations revealed that age, thresholds at 16 kHz, 12.5 kHz, etc., on the order of importance, contributed to SRT. These results suggest the importance of hearing in the extended high frequencies for predicting speech-in-noise recognition in listeners with normal audiograms.

Effect of Sensory Modality on Reaction Time in Individuals with Auditory Neuropathy Spectrum Disorder.

PURPOSE: To investigate and compare the reaction time of individuals with auditory neuropathy in three modalities, auditory, visual, and audio-visual. The reaction time of individuals with auditory neuropathy was also compared with those with normal hearing. The relationship between reaction time across modalities and the duration of hearing loss in auditory neuropathy was also investigated. METHODS AND MATERIALS: The reaction time of adults with auditory neuropathy and those with normal hearing was measured in the three modalities using the Choice reaction time task. RESULTS: The auditory neuropathy group significantly had a longer reaction time than the normal hearing in all modalities. The trend of the mean reaction time differed across groups. Further, a significant difference in reaction time of the auditory neuropathy group was noted between auditory and visual mode, auditory and audio-visual mode. However, no significant difference between visual and audio-visual modalities was noted in reaction time. CONCLUSION: Significantly longer reaction time in auditory neuropathy is presumed to have resulted from neural conduction delay and impaired processing. The auditory neuropathy group can utilize visual cues for faster processing, and the study recommends an audio-visual mode for their management. In addition, the duration of hearing loss in auditory neuropathy had no relationship with reaction time across all modalities.

The Genome of the Mimosoid Legume Prosopis cineraria, a Desert Tree.

The mimosoid legumes are a clade of ~40 genera in the Caesalpinioideae subfamily of the Fabaceae that grow in tropical and subtropical regions. Unlike the better studied Papilionoideae, there are few genomic resources within this legume group. The tree Prosopis cineraria is native to the Near East and Indian subcontinent, where it thrives in very hot desert environments. To develop a tool to better understand desert plant adaptation mechanisms, we sequenced the P. cineraria genome to near-chromosomal assembly, with a total sequence length of ~691 Mb. We predicted 77,579 gene models (76,554 CDS, 361 rRNAs and 664 tRNAs) from the assembled genome, among them 55,325 (~72%) protein-coding genes that were functionally annotated. This genome was found to consist of over 58% repeat sequences, primarily long terminal repeats (LTR-)-retrotransposons. We find an expansion of terpenoid metabolism genes in P. cineraria and its relative Prosopis alba, but not in other legumes. We also observed an amplification of NBS-LRR disease-resistance genes correlated with LTR-associated retrotransposition, and identified 410 retrogenes with an active burst of chimeric retrogene creation that approximately occurred at the same time of divergence of P. cineraria from a common lineage with P. alba~23 Mya. These retrogenes include many biotic defense responses and abiotic stress stimulus responses, as well as the early Nodulin 93 gene. Nodulin 93 gene amplification is consistent with an adaptive response of the species to the low nitrogen in arid desert soil. Consistent with these results, our differentially expressed genes show a tissue specific expression of isoprenoid pathways in shoots, but not in roots, as well as important genes involved in abiotic salt stress in both tissues. Overall, the genome sequence of P. cineraria enriches our understanding of the genomic mechanisms of its disease resistance and abiotic stress tolerance. Thus, it is a very important step in crop and legume improvement.

Salt flat microbial diversity and dynamics across salinity gradient.

Sabkhas are hypersaline, mineral-rich, supratidal mudflats that harbor microbes that are adapted to high salt concentration. Sabkha microbial diversity is generally studied for their community composition, but less is known about their genetic structure and heterogeneity. In this study, we analyzed a coastal sabkha for its microbial composition using 16S rDNA and whole metagenome, as well as for its population genetic structure. Our 16S rDNA analysis show high alpha diversity in both inner and edge sabkha than outer sabkha. Beta diversity result showed similar kind of microbial composition between inner and edge sabkha, while outer sabkha samples show different microbial composition. At phylum level, Bacteroidetes (~ 22 to 34%), Euryarchaeota (~ 18 to ~ 30%), unclassified bacteria (~ 24 to ~ 35%), Actinobacteria (~ 0.01 to ~ 11%) and Cyanobacteria (less than 1%) are predominantly found in both inside and edge sabkha regions, whereas Proteobacteria (~ 92 to ~ 97%) and Parcubacteria (~ 1 to ~ 2%) are predominately found in outer sabkha. Our 225 metagenomes assembly from this study showed similar bacterial community profile as observed in 16S rDNA-based analysis. From the assembled genomes, we found important genes that are involved in biogeochemical cycles and secondary metabolite biosynthesis. We observed a dynamic, thriving ecosystem that engages in metabolic activity that shapes biogeochemical structure via carbon fixation, nitrogen, and sulfur cycling. Our results show varying degrees of horizontal gene transfers (HGT) and homologous recombination, which correlates with the observed high diversity for these populations. Moreover, our pairwise population differentiation (Fst) for the abundance of species across the salinity gradient of sabkhas identified genes with strong allelic differentiation, lower diversity and elevated nonsynonymous to synonymous ratio of variants, which suggest selective sweeps for those gene variants. We conclude that the process of HGT, combined with recombination and gene specific selection, constitute the driver of genetic variation in bacterial population along a salinity gradient in the unique sabkha ecosystem.

Transcriptome Profiling and Functional Validation of RING-Type E3 Ligases in Halophyte Sesuvium verrucosum under Salinity Stress.

Owing to their sessile nature, plants have developed a tapestry of molecular and physiological mechanisms to overcome diverse environmental challenges, including abiotic stresses. Adaptive radiation in certain lineages, such as Aizoaceae, enable their success in colonizing arid regions and is driven by evolutionary selection. Sesuvium verrucosum (commonly known as Western sea-purslane) is a highly salt-tolerant succulent halophyte belonging to the Aizoaceae family; thus, it provides us with the model-platform for studying plant adaptation to salt stress. Various transcriptional and translational mechanisms are employed by plants to cope with salt stress. One of the systems, namely, ubiquitin-mediated post-translational modification, plays a vital role in plant tolerance to abiotic stress and other biological process. E3 ligase plays a central role in target recognition and protein specificity in ubiquitin-mediated protein degradation. Here, we characterize E3 ligases in Sesuvium verrucosum from transcriptome analysis of roots in response to salinity stress. Our de novo transcriptome assembly results in 131,454 transcripts, and the completeness of transcriptome was confirmed by BUSCO analysis (99.3% of predicted plant-specific ortholog genes). Positive selection analysis shows 101 gene families under selection; these families are enriched for abiotic stress (e.g., osmotic and salt) responses and proteasomal ubiquitin-dependent protein catabolic processes. In total, 433 E3 ligase transcripts were identified in S. verrucosum; among these transcripts, single RING-type classes were more abundant compared to multi-subunit RING-type E3 ligases. Additionally, we compared the number of single RING-finger E3 ligases with ten different plant species, which confirmed the abundance of single RING-type E3 ligases in different plant species. In addition, differential expression analysis showed significant changes in 13 single RING-type E3 ligases (p-value < 0.05) under salinity stress. Furthermore, the functions of the selected E3 ligases genes (12 genes) were confirmed by yeast assay. Among them, nine genes conferred salt tolerance in transgenic yeast. This functional assay supports the possible involvement of these E3 ligase in salinity stress. Our results lay a foundation for translational research in glycophytes to develop stress tolerant crops.

Benefit on daily listening with technological advancements: comparison of basic and premium category hearing aids.

PURPOSE: The aim of the study was to compare the user-rated benefit of two categories of hearing aids, mainly the basic and premium categories of hearing aids. METHODS: A questionnaire was administered on 102 hearing aids users (47 basic and 55 premium category users) with severity of hearing loss ranging from mild to moderately severe sensorineural hearing loss. The questionnaire administered was divided into mainly seven subscales which included speech intelligibility in quiet and in noise, ease of communication, the efficiency of noise reduction, localization, quality of music perception and cost effectiveness. The effect of duration of daily usage of hearing aids on performance among these different subscales was also assessed. RESULTS: Ease of communication was rated better by premium hearing aid users, whereas the cost effectiveness was rated to be better by basic users. There was no significant difference observed between performances of basic versus premium category of hearing aids in other listening domains assessed. There was no significant difference in any of the listening domains with daily usage duration for both categories of hearing aid users. CONCLUSION: The users of premium category devices revealed better ease of communication in daily environments, whereas performance of these devices on other listening domains remains questionable. Cost effectiveness was reported to be better by the users of basic hearing aids. A prospective and controlled paired series comparison of hearing aid performance needs to be performed to confirm these findings.

Dynamics of Speech Perception in the Auditory-Visual Mode: An Empirical Evidence for the Management of Auditory Neuropathy Spectrum Disorders.

BACKGROUND AND OBJECTIVES: The present study probed into the relative and combined contribution of auditory and visual modalities in the speech perception of individuals with auditory neuropathy spectrum disorders (ANSD). Specifically, the identification scores of consonantvowel (CV) syllables, visual enhancement (VE), and auditory enhancement in different signal to noise ratios (SNRs) were compared with that of the control group. Subjects and. METHODS: The study used a repeated measure standard group comparison research design. Two groups of individuals in the age range of 16 to 35 years participated in the study. The clinical group included 35 participants diagnosed as ANSD, while the control group had 35 age and gender matched individuals with typical auditory abilities. The participants were assessed for CV syllable identification in auditory only (A), visual only (V), and auditory-visual (AV) modalities. The syllables were presented in quiet and at 0 dB SNR. RESULTS: The speech identification score was maximum in AV condition followed by A-condition and least in V condition. This was true in both the groups. The individuals with ANSD were able to make better use of visual cues than the control group, as evident in the VE score. CONCLUSIONS: The dynamics of speech perception in the AV mode is different between ANSD and control. There is definite benefit of auditory as well as visual cues to individuals with ANSD, suggesting the need to facilitate both the modalities as part of the audiological rehabilitation. Future studies can focus on independently facilitating the two modalities and testing the benefits in the AV mode of speech perception in individuals with ANSD.