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.

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.

The efferent auditory pathway is known to alter the cochlear electrical properties, at low stimulus levels. This study aims to identify the effect of activation of the efferent auditory pathway through contralateral wide- and narrow-band noise at high sound levels. Acoustical reflex threshold and acoustical reflex amplitude (at ART + 10 dB) were obtained at three frequencies (500 Hz, 1 kHz, 2 kHz) in 60 normally hearing subjects, in the presence and absence of contralateral wide-and narrow-band noise (centred around reflex activating stimuli) at 30 dB SL. Results showed a consistent reduction in amplitude, and an increase in threshold, for 1- and 2-kHz tones in the presence of contralateral wideband but not narrow-band noise. Results are discussed with reference to the electrical properties of the cochlea, and the response properties of the efferent auditory pathway and cochlear nucleus.

<b><i>Background:</i></b> 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. <b><i>Methods:</i></b> 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). <b><i>Results:</i></b> The results revealed significant differences in TMTF between AWS and AWNS, but no differences were found in the gap detection thresholds. <b><i>Conclusions:</i></b> 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.

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.