Middle Ear Muscle Reflex in Normal-Hearing Individuals with Occupational Noise Exposure.

Objectives: Noise-induced cochlear synaptopathy is studied extensively in animal models. The diagnosis of synaptopathy in humans is challenging and the roles of many noninvasive measures in identifying synaptopathy are being explored. The acoustic middle ear muscle reflex (MEMR) can be considered as a vital tool since noise exposure affects the low-spontaneous rate fibers that play an important role in elicitation of MEMR. The present study aimed at measuring MEMR threshold and MEMR strength. Design: The study participants were divided into two groups. All the participants had normal-hearing thresholds. The control group consisted of 25 individuals with no occupational noise exposure whereas noise exposure group had 25 individuals who were exposed to occupational noise of 85 dBA for a minimum period of 1 year. MEMR threshold and strength was assessed for pure tones (500 Hz and 1000 Hz) and broadband noise. Results: The results showed that the MEMR threshold was similar in both the groups. MEMR strength was reduced in noise exposure group compared to control group. Conclusions: The results of the study suggest that MEMR strength could be used as a sensitive measure in identifying cochlear synaptopathy with careful consideration of the stimulus characteristics.

Effect of Quiet and Noise on P300 Response in Individuals with Auditory Neuropathy Spectrum Disorder

Abstract Introduction Auditory neuropathy spectrum disorder (ANSD) is a clinical condition in which individuals have normal cochlear responses and abnormal neural responses. There is a lack of evidence in the literature regarding the neural discrimination skill in individuals with ANSD, especially when the signal is presented in the presence of noise. Objectives The present study was performed with the aim to investigate auditory discrimination skill, in quiet and in the presence of noise, in individuals with ANSD and to compare the findings with normal-hearing individuals. Methods A total of 30 individuals with normal hearing sensitivity and 30 individuals with ANSD in the age range of 15 to 55 years old, with the mean age of 27.86 years old, were the participants. P300 response was recorded from both groups using syllable pairs /ba/-/da/ in oddball paradigm and the syllable /da/ in repetitive paradigm in quiet and at +10 dB signal-to-noise ratio (SNR). Results There was significant prolongation in latency and reaction time, and reduction in amplitude of P300 response and sensitivity in both groups with the addition of noise. The topographic pattern analysis showed activation of the central-parietal-occipital region of the brain in individuals with ANSD, whereas activation of the central-parietal region was observed in individuals with normal hearing. The activation was more diffused in individuals with ANSD compared with that of individuals with normal hearing. Conclusion The individuals with ANSD showed a significantly more adverse effect of noise on the neural discrimination skill than the normal counterpart.

Effect of Quiet and Noise on P300 Response in Individuals with Auditory Neuropathy Spectrum Disorder.

Introduction Auditory neuropathy spectrum disorder (ANSD) is a clinical condition in which individuals have normal cochlear responses and abnormal neural responses. There is a lack of evidence in the literature regarding the neural discrimination skill in individuals with ANSD, especially when the signal is presented in the presence of noise. Objectives The present study was performed with the aim to investigate auditory discrimination skill, in quiet and in the presence of noise, in individuals with ANSD and to compare the findings with normal-hearing individuals. Methods A total of 30 individuals with normal hearing sensitivity and 30 individuals with ANSD in the age range of 15 to 55 years old, with the mean age of 27.86 years old, were the participants. P300 response was recorded from both groups using syllable pairs /ba/-/da/ in oddball paradigm and the syllable /da/ in repetitive paradigm in quiet and at +10 dB signal-to-noise ratio (SNR). Results There was significant prolongation in latency and reaction time, and reduction in amplitude of P300 response and sensitivity in both groups with the addition of noise. The topographic pattern analysis showed activation of the central-parietal-occipital region of the brain in individuals with ANSD, whereas activation of the central-parietal region was observed in individuals with normal hearing. The activation was more diffused in individuals with ANSD compared with that of individuals with normal hearing. Conclusion The individuals with ANSD showed a significantly more adverse effect of noise on the neural discrimination skill than the normal counterpart.

Detection of Gap and Modulations: Auditory Temporal Resolution Deficits in Adults Who Stutter.

BACKGROUND: Recent models of speech production suggest a link between speech production and perception. Persons with stuttering are known to have deficits in sensorimotor timing and exhibit auditory processing problems. Most of the earlier studies have focused on assessing temporal ordering in adults who stutter (AWS), but limited attempts have been made to document temporal resolution abilities in AWS. METHODS: A group of 16 AWS and 16 age- and gender-matched adults who do not stutter (AWNS) were recruited for the study. Temporal resolution abilities were assessed using the Gap Detection Test and temporal modulation transfer function (TMTF). RESULTS: The results revealed significant differences in TMTF between AWS and AWNS, but no differences were found in the gap detection thresholds. CONCLUSIONS: Results suggest that the sensory representations of the temporal modulations are compromised in AWS, which may contribute to the programming of rhythmic movements during speech planning.

Speech Perception in Quiet and in Noise Condition in Individuals with Auditory Neuropathy Spectrum Disorder.

OBJECTIVE: The study investigated the effect of noise on syllable perception in individuals with Auditory Neuropathy Spectrum Disorder (ANSD) and compared that with the normal hearing individuals. MATERIALS AND METHODS: A total of 54 participants were considered, out of which 26 individuals were diagnosed with ANSD and 28 with normal hearing sensitivity. Syllable identification and discrimination were assessed in both the groups in quiet as well as +10 dB SNR. RESULTS: All the individuals with ANSD performed poorer on syllable identification and syllable discrimination tasks compared to individuals with normal hearing. Information transfer and d-prime analyses revealed that noise affects the perception of voicing information in individuals with ANSD compared to place and manner information. Among the consonants tested, /pa/ was more resistant to noise. CONCLUSION: Noise had deleterious effects on speech perception in individuals with ANSD. Low-frequency information appears to be more susceptible to the effects of noise in individuals with ANSD.

The Effect of Short-Term Musical Training on Speech Perception in Noise.

The aim of the study was to assess the effect of short-term musical training on speech perception in noise. In the present study speech perception in noise was measured pre- and post- short-term musical training. The musical training involved auditory perceptual training for raga identification of two Carnatic ragas. The training was given for eight sessions. A total of 18 normal hearing adults in the age range of 18-25 years participated in the study wherein group 1 consisted of ten individuals who underwent musical training and group 2 consisted of eight individuals who did not undergo any training. Results revealed that post training, speech perception in noise improved significantly in group 1, whereas group 2 did not show any changes in speech perception scores. Thus, short-term musical training shows an enhancement of speech perception in the presence of noise. However, generalization and long-term maintenance of these benefits needs to be evaluated.

Short-Term Musical Training and Pyschoacoustical Abilities.

The aim of the study was to assess the effect of short-term perceptual training of music on some psycho-acoustical measures. The study was carried out in three phases. In first the phase pre-training evaluation was done which included raga identification and various psycho acoustical tests. Psycho-acoustical tests included measurement of differential limen of frequency and intensity, duration discrimination, gap detection, modulation detection, backward masking and duration pattern test. In the second phase, auditory perceptual training was given for raga identification and in the third phase post- training evaluation was done though same tests as mentioned in pre-training phase. A total of 10 normal hearing adults (7 males, 3 females) in the age range of 18-25 years participated in the study. The results revealed that all the subjects performed significantly better on raga identification after training. However; there was no significant difference in psycho-acoustical measures in pre and post-training.

Temporal processing abilities across different age groups.

BACKGROUND: Psychophysical evidence indicates age-related decline over a broad range of auditory abilities. Thus, age-related deterioration in temporal processing abilities also may be expected. At issue is whether the various dimensions of temporal processing decline at the same or at different rates across age. PURPOSE: To determine whether various temporal processes decline with aging and whether some are more resistant to the effects of aging than others. STUDY SAMPLE: A total of 176 subjects in the age range from 20 to 85 yr participated in this research. Subjects were divided into six cross-sectional age groups. There were 30 subjects per age decade up to 70 yr and 26 subjects in the age group >70 yr. DATA COLLECTION AND ANALYSIS: Temporal processing was evaluated using gap detection, duration discrimination, modulation detection, and duration pattern. RESULTS: Individuals in the 20-30 and 30-40 yr groups performed significantly better in all the psychoacoustic measures in comparison to other age groups. Deterioration in temporal processing began after the fourth decade of life. Deterioration accelerated after 70 yr of age. CONCLUSIONS: There is a systematic, age-related decline in temporal processing starting from the fourth decade of life. The deficits in temporal processing observed in the present study may be related in part to the difficulties that elderly persons encounter in noisy listening situations.

Perceptual learning of non-native speech contrast and functioning of the olivocochlear bundle.

The purpose of this study was to investigate the relationship between perceptual learning of non-native speech sounds and strength of feedback in the medial olivocochlear bundle (MOCB). Discrimination abilities of non-native speech sounds (Malayalam) from its native counterparts (Hindi) were monitored during 12 days of training. Contralateral inhibition of otoacoustic emissions were measured on the first and twelfth day of training. Results suggested that training significantly improved reaction time and accuracy of identification of non-native speech sounds. There was a significant positive correlation between the slope (linear) of identification scores and change in distortion product otoacoustic emission inhibition at 3000 Hz. Findings suggest that during perceptual learning feedback from the MOCB may fine tune the brain stem and/or cochlea. However, such a change, isolated to a narrow frequency region, represents a limited effect and needs further exploration to confirm and/or extend any generalization of findings.

Auditory processing in individuals with auditory neuropathy.

BACKGROUND: Auditory neuropathy is a disorder characterized by no or severely impaired auditory brainstem responses in presence of normal otoacoustic emissions and/or cochlear microphonics. Speech perception abilities in these individuals are disproportionate to their hearing sensitivity and reported to be dependent on cortical evoked potentials and temporal processing abilities. The disproportionate loss of auditory percept in presence of normal cochlear function is suggestive of impairment of auditory neural synchrony. METHODS: We studied the auditory evoked potentials and psychophysical abilities in 14 adults with auditory neuropathy to characterize their perceptual capabilities. Psychophysical tests included measurement of open set speech identification scores, just noticeable difference for transition duration of syllable /da/ and temporal modulation transfer function. Auditory evoked potentials measures were, recording of P1/N1, P2/N2 complex and mismatch negativity (MMN). RESULTS: Results revealed a significant correlation between temporal processing deficits and speech perception abilities. In majority of individuals with auditory neuropathy P1/N1, P2/N2 complex and mismatch negativity could be elicited with normal amplitude and latency. None of the measured evoked potential parameters correlated with the speech perception scores. Many of the subjects with auditory neuropathy showed normal MMN even though they could not discriminate the stimulus contrast behaviorally. CONCLUSION: Conclusions drawn from the study are: 1. Individuals with auditory neuropathy have severely affected temporal processing. 2. The presence of MMN may not be directly linked to presence of behavioral discrimination and to speech perception capabilities at least in adults with auditory neuropathy.