Neurophysiological aspects of brainstem processing of speech stimuli in audiometric-normal geriatric population.

OBJECTIVE: Poor auditory speech perception in geriatrics is attributable to neural de-synchronisation due to structural and degenerative changes of ageing auditory pathways. The speech-evoked auditory brainstem response may be useful for detecting alterations that cause loss of speech discrimination. Therefore, this study aimed to compare the speech-evoked auditory brainstem response in adult and geriatric populations with normal hearing. METHODS: The auditory brainstem responses to click sounds and to a 40 ms speech sound (the Hindi phoneme |da|) were compared in 25 young adults and 25 geriatric people with normal hearing. The latencies and amplitudes of transient peaks representing neural responses to the onset, offset and sustained portions of the speech stimulus in quiet and noisy conditions were recorded. RESULTS: The older group had significantly smaller amplitudes and longer latencies for the onset and offset responses to |da| in noisy conditions. Stimulus-to-response times were longer and the spectral amplitude of the sustained portion of the stimulus was reduced. The overall stimulus level caused significant shifts in latency across the entire speech-evoked auditory brainstem response in the older group. CONCLUSION: The reduction in neural speech processing in older adults suggests diminished subcortical responsiveness to acoustically dynamic spectral cues. However, further investigations are needed to encode temporal cues at the brainstem level and determine their relationship to speech perception for developing a routine tool for clinical decision-making.

Construction of Hindi Speech Stimuli for Eliciting Auditory Brainstem Responses.

Speech-evoked auditory brainstem responses (spABRs) provide considerable information of clinical relevance to describe auditory processing of complex stimuli at the sub cortical level. The substantial research data have suggested faithful representation of temporal and spectral characteristics of speech sounds. However, the spABR are known to be affected by acoustic properties of speech, language experiences and training. Hence, there exists indecisive literature with regards to brainstem speech processing. This warrants establishment of language specific speech stimulus to describe the brainstem processing in specific oral language user. The objective of current study is to develop Hindi speech stimuli for recording auditory brainstem responses. The Hindi stop speech of 40 ms containing five formants was constructed. Brainstem evoked responses to speech sound |da| were gained from 25 normal hearing (NH) adults having mean age of 20.9 years (SD = 2.7) in the age range of 18-25 years and ten subjects (HI) with mild SNHL of mean 21.3 years (SD = 3.2) in the age range of 18-25 years. The statistically significant differences in the mean identification scores of synthesized for speech stimuli |da| and |ga| between NH and HI were obtained. The mean, median, standard deviation, minimum, maximum and 95 % confidence interval for the discrete peaks and V-A complex values of electrophysiological responses to speech stimulus were measured and compared between NH and HI population. This paper delineates a comprehensive methodological approach for development of Hindi speech stimuli and recording of ABR to speech. The acoustic characteristic of stimulus |da| was faithfully represented at brainstem level in normal hearing adults. There was statistically significance difference between NH and HI individuals. This suggests that spABR offers an opportunity to segregate normal speech encoding from abnormal speech processing at sub cortical level, which implies that alterations in brainstem responses have clinical significance to identify the subjects with possible processing disorders.

Acoustic analysis of speech of cochlear implantees and its implications.

OBJECTIVES: Cochlear implantees have improved speech production skills compared with those using hearing aids, as reflected in their acoustic measures. When compared to normal hearing controls, implanted children had fronted vowel space and their /s/ and /∫/ noise frequencies overlapped. Acoustic analysis of speech provides an objective index of perceived differences in speech production which can be precursory in planning therapy. The objective of this study was to compare acoustic characteristics of speech in cochlear implantees with those of normal hearing age matched peers to understand implications. METHODS: Group 1 consisted of 15 children with prelingual bilateral severe-profound hearing loss (age, 5-11 years; implanted between 4-10 years). Prior to an implant behind the ear, hearing aids were used; prior & post implantation subjects received at least 1 year of aural intervention. Group 2 consisted of 15 normal hearing age matched peers. Sustained productions of vowels and words with selected consonants were recorded. Using Praat software for acoustic analysis, digitized speech tokens were measured for F1, F2, and F3 of vowels; centre frequency (Hz) and energy concentration (dB) in burst; voice onset time (VOT in ms) for stops; centre frequency (Hz) of noise in /s/; rise time (ms) for affricates. A t-test was used to find significant differences between groups. RESULTS: Significant differences were found in VOT for /b/, F1 and F2 of /e/, and F3 of /u/. No significant differences were found for centre frequency of burst, energy concentration for stops, centre frequency of noise in /s/, or rise time for affricates. These findings suggest that auditory feedback provided by cochlear implants enable subjects to monitor production of speech sounds. CONCLUSION: Acoustic analysis of speech is an essential method for discerning characteristics which have or have not been improved by cochlear implantation and thus for planning intervention.

Age of identification of hearing impairment in Mumbai--a trend analysis.

UNLABELLED: Implementation of Universal Newborn Hearing Screening (UNHS) has led to lowering the age of identification of congenital hearing loss in children. In the absence of UNHS in Mumbai (India), it is pertinent to establish a data base on the age of identification of permanent hearing loss in children to facilitate affirmative action. OBJECTIVE: To study the trend in age of identification (AOI) of hearing impairment in children studying in special schools. METHODS: This retrospective study was a survey conducted on a convenient sample. The authentic data about date of birth and age of identification (AOI) of 510 children were collected through parental interview, and scrutiny of documents like birth certificates, first audiological report maintained in special schools/institutes/hospitals. RESULTS: Time series analysis of the data concluded that from 1989 to 2008, AOI has reduced by 9.59 months. AOI has not reached one year even by 2008 and is much below the target of three months of age as per the recommendation of Joint Committee on Infant Hearing (2007). CONCLUSION: In absence of Universal Newborn Hearing Screening (UNHS) in Mumbai (India) the present efforts do not seem to be enough in lowering the age of identification of hearing loss and policy decision is warranted.

Studying tinnitus in the ICF framework.

Activity limitation and participation restriction (AL/PR) on account of tinnitus was studied in the ICF framework in order to understand how tinnitus restricts individuals from fulfilling social and economic obligations. The objective of the study was to study the impact of tinnitus in the framework of ICF. Twenty-one adults in the age range of 20-60 years with chronic tinnitus (>3 months) and with normal hearing sensitivity were included in the study. THI was mapped to the framework of ICF. Twenty out of twenty-five items belonged to the domains under body function and five items addressed AL/PR. Five more AL/PR items applicable to tinnitus were added to THI. The THI+ICF questionnaire tested well on test reliability (0.987) and internal consistency (0.873). Body function was significantly more affected than AL/PR (P = 0.0005). These results suggest that tinnitus does not result in significant AL/PR from the ICF perspective. Further, psycho-acoustic characteristics such as intensity, frequency of tinnitus, and time since onset of tinnitus have only minimal if any impact on AL/PR.

A novel locus DFNA59 for autosomal dominant nonsyndromic hearing loss maps at chromosome 11p14.2-q12.3.

Autosomal dominant nonsyndromic hearing loss (ADNSHL) accounts for about one-fifth of hereditary hearing loss in humans. In the present study, we have analyzed a three-generation family with 14 of its members manifesting ADNSHL, using a genome-wide linkage mapping approach. We found a novel locus DFNA59 between the D11S929 and D11S480 markers in the chromosome location 11p14.2-q12.3. The highest two-point lod score of 5.72 at recombination fraction = 0 was obtained for D11S4152, D11S4154, D11S1301, D11S905 and D11S1344. The critical genomic region comprising about 37 megabases of DNA is proposed to carry a gene for ADNSHL in the family. About 50 cochlear-expressed genes mapping to the region are strong candidates which we propose to examine to identify the gene responsible for the hearing impairment.

Implications in disclosing auditory genetic mutation to a family: a case study.

The aim of the study is to understand the implications of disclosing the results of connexin26 (Cx26) gene testing to the concerned family with hearing impaired individuals. The department of biotechnology is funding a multicentric multidisciplinary team from Jawaharlal Nehru Center for Advanced Scientific Research (Bangalore), AYJNIHH (Mumbai), PGIBMS (Chennai), and MAMC (New Delhi) to profile mutations of deafness genes in India. Under this program, blood samples were taken from various centers and were sent to JNCASR for genetic analysis (screening for Cx26 mutations). This case study is an attempt to bring out issues encountered when disclosing the implications of genetic diagnosis to the concerned family.