Ravi Sockalingam

Automatic auditory processing of English words as indexed by the mismatch negativity, using a multiple deviant paradigm

Objective: The aim of this study was to investigate mismatch negativity (MMN) responses to a variety of speech stimuli (/de:/, /ge:/, /deI/ “day”, and /geI/ “gay”) in a multiple deviant paradigm. It was hypothesized that all speech stimulus contrasts in the multiple deviant paradigm, including the fine acoustic speech contrast [d/g], would elicit robust MMN responses and that consonant vowel (CV) real word deviants (e.g., “day” and “gay”) would elicit larger MMN responses than CV nonword deviants (e.g., “de” and “ge”) within and across experimental contrasts. Design: Ten healthy, right-handed, native English–speaking adults (23.4 ± 2.27 yr) with normal hearing were presented with 12 blocks of stimuli, using a multiple deviant oddball paradigm. Each of the four speech stimuli were presented as standards (p = 0.7) in three blocks, with the remaining stimuli acting as deviants (p = 0.1 each). Subjects were also presented with the same stimuli in a behavioral discrimination task. Results: MMN responses to the fine acoustic speech contrast [d/g] (e.g., “de” versus “ge”, “day” versus “gay”) did not reach significance. However, a significant and larger MMN response was obtained at an earlier latency to the real word deviants among nonword standards with the same initial consonant (i.e., de→day, ge→gay) when compared with the responses to nonword deviants among word standards (day→de, gay→ge). Conclusions: The results showed that MMN responses could be elicited by speech stimuli with large, single acoustic deviances, within a multiple deviant paradigm design. This result has positive clinical implications for the testing of subjects who may only tolerate short testing sessions (e.g., pathological populations) in that responses to a wider range of speech stimuli may be recorded without necessarily having to increase session length. The results also demonstrated that MMN responses were elicited by large, single acoustic deviances but not fine acoustic deviances within the speech stimuli. The poor results for the fine acoustic deviances support previous studies that have used single contrast paradigms and found that when carefully controlled methodological designs and strict methods of analysis are applied, robust responses to fine-grained CV syllable contrasts may be difficult to obtain. The enhanced MMN observed in response to the real word deviants among nonword standards may provide further evidence for the presence of long-term neural traces for words in the brain, however possible contextual effects limit the interpretation of these data. Further research is needed to investigate the ability of the MMN response to accurately reflect speech sounds with fine acoustic contrasts, as well as the ability of the MMN to reflect neural traces for words in the brain, before it can be reliably used as a clinical tool in the investigation of spoken word processing in pathological populations.

Cisplatin-Induced Ototoxicity and Pharmacokinetics: Preliminary Findings in a Dog Model

The early effects of a clinical dose of cisplatin (100 mg/m2) on distortion-product otoacoustic emissions (DPOAE) thresholds and the relationship between DPOAE threshold shifts and changes in plasma concentrations of filterable and total platinum (Pt) following infusion of cisplatin in a dog model were investigated. The DPOAE thresholds (based on input-output function) were measured 2 days before a single high dose of cisplatin administration, and compared with measurements recorded 2 and 4 days after infusion. The results revealed DPOAE thresholds to be elevated by 4 days after the administration of cisplatin. However, this elevation could not be correlated with plasma concentrations of filterable and total Pt, which showed little variation over the 48-hour postinfusion period between animals. The present study demonstrated that DPOAE thresholds have the potential to be used as an indicator of cisplatin-induced ototoxicity, and cisplatin-induced ototoxicity could not be explained by plasma Pt kinetics in individual animals.

Transient-Evoked and 2F1-F2 Distortion Product Oto-Acoustic Emissions in Dogs:Preliminary Findings

Transient (click)-evoked oto-acoustic emissions (TEOAEs) and distortion product oto-acoustic emissions (DPOAEs) were recorded in a feasibility study in 7 healthy mixed-breed dogs using the ILO 92 OAE analyser (Otodynamics, Hartfield, UK). Five dogs were found to have normal hearing in both ears and 2 dogs in the left ear only following otoscopy, tympanometry and auditory brainstem response audiometry. Twelve sets of TEOAEs (click-evoked) to 80 dB peSPL click stimulus and 9 sets of DPOAEs (2F1-F2) to 8 different stimulus levels of the primary tones (L1/L2) were collected at 11 test frequencies (F2) in these normal-hearing dogs. TEOAEs were successfully recorded in 11 of the 12 ears using the default user setting and in all 12 ears using the quickscreen program. DPOAEs were successfully recorded in all 9 ears tested. While the TEOAEs parameters matched those for humans, the average signal-to-noise ratio of DPOAEs was considerably higher in the dogs. Stimulus levels at 55/55, 55/45 and 55/35 dB SPL were demonstrated to produce DPOAEs that seem to reflect the active dynamic status of the outer hair cell system. Postmortem DPOAEs at these stimulus levels and TEOAEs at 80 Db peSPL could not be elicited 5 min following euthanasia of dogs. However, DPOAEs could still be recorded albeit with reduced amplitude at stimulus levels where L1 > 55 dB SPL. The results suggest that TEOAEs and DPOAEs in dogs have the potential to provide valuable insights into their mechanisms of generation, and the specific role and behaviour of outer hair cells of the cochlea in certain pathological conditions, particularly in drug-induced ototoxicity, in humans.

Test-retest reliability of distortion-product otoacoustic emissions in children with normal hearing: a preliminary study.

The test-retest reliability of DPOAEs was investigated in 24 children (43 ears) with normal hearing at five F2 frequencies (2530, 3561, 5014, 7029, and 10 028 Hz). Two DPOAE recordings were performed on the same subjects in the same location using the same equipment. The second recordings were made 13 to 15 days after the first recording. The DPOAE level recorded in the subjects ranged between -13.10 and 20.20 dB for all the five frequencies. The variation in DPOAE level was greater at 10 028 Hz than at other frequencies. The mean difference between the test and retest recordings was 0.52±2.87, −1.57±4.62, 0.01±3.38, −0.55±2.85, and −0.56±5.57dB at 2530, 3561, 5014, 7029, and 10 028 Hz, respectively. The intra-correlation coefficients for DPOAE level at each of the five (F2) frequencies were 0.85, 0.68, 0.62, 0.89, and 0.64 respectively. Calculations of mean +2SD showed that retest recordings greater than 6.26, 7.67, 6.81, 5.15, and 10.58 dB SPL at 2530, 3561, 5014, 7029, and 10 028 Hz respectively could possibly be interpreted as a significant change in status of the ear.

Effectiveness of frequency-matched masking and residual inhibition in tinnitus therapy: A preliminary study

Various methods have been used to treat tinnitus, which is a perceived sound in one or both ears, or in the head. The present study investigates residual inhibition, which is the reduction or elimination of tinnitus perception, by employing a commercially available software package designed to precisely match various sounds to a persons tinnitus. The purpose of the present study was to identify what type of sound, if any, will reduce or eliminate the tinnitus. In addition, an attempt was made to investigate the effect of stimulus duration on residual inhibition duration. Ten patients who had had tinnitus for longer than a year were recruited for the study. Six (60%) of these patients reported a mild handicap from their tinnitus on the Tinnitus Handicap Inventory. All ten patients matched their tinnitus to a frequency-matched stimulus. Descriptive analyses indicated that frequency-matched stimuli elicited longer residual inhibition duration than did non-frequency-matched stimuli. Additionally, more patients responded with residual inhibition to frequency-matched stimuli than to non-frequency-matched. Finally, partial inhibition was elicited more often than complete inhibition, regardless of stimulus type. Results suggested that the closer a stimulus can be matched to the patients own tinnitus the more likely it is that a patient can get relief from listening to it.

Feasibility of establishing an early indicator for ototoxicity in children using otoacoustic emissions

Abstract The present study aimed to investigate the feasibility of establishing an early indicator for ototoxicity in children using OAEs. The participants included an experimental group of four pediatric oncology patients (aged 4 to 7 years) undergoing chemotherapy. Participants were tested at least, twice (the first test being the baseline) using pure-tone audiometry, tympanometry, distortion product otoacoustic emissions (DPOAEs) (with stimulus intensity levels of 65/55 and 50/40 dB SPL), and transient evoked otoacoustic emissions (TEOAEs). The difference in OAE measures between two tests were recorded and compared with the results obtained from a control group of 10 normal hearing children (mean age = 7.7 years, SD = 3.3 years) using the same test battery, which provided the test–retest reliability data. A change in OAEs between two consecutive tests for the four pediatric oncology patients was considered significant if it exceeded the mean plus 2 SD of that of the control group. The results indicated that depending on the type of OAE procedure used, the pattern of OAE changes due to ototoxicity could possibly exhibit either one, or both, of the following characteristics: an increase in low-to mid-frequency emissions and a decrease in high-frequency emissions. This pattern of OAE changes may serve as an early indicator for ototoxicity in children. The DP-gram (65/55) was found to be the most sensitive tool to detect early changes of the cochlea due to ototoxicity. However, these conclusions are tentative given the small sample size of the study.

Test-retest reliability of distortion-product otoacoustic emissions in children with normal hearing: A preliminary study(vol 46:7 (351-354) 2007)

Due to an oversight the article entitled “Test-Retest Reliability of Distortion-Product Otoacoustic Emissions in Children with Normal Hearing: A Preliminary Study” in the International Journal of Audiology Volume 46, Issue 7, pp. 351–354, was published with an incorrect author line up and affiliations. The correct author line up and affiliations is below. Ravi Sockalingam1, Juyoune Lee Choi2, Daeho Choi2, and Joseph Kei3. 1. Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand 2. Dalhousie University, Halifax, Nova Scotia, Canada 3. Division of Audiology, The University of Queensland, Brisbane, Australia

Effectiveness of Frequency-Matched Masking and Residual Inhibition in Tinnitus Therapy

Abstract The present study investigates residual inhibition, which is the reduction or elimination of tinnitus perception, by employing a commercially available software package designed to precisely match various sounds to a persons tinnitus. In addition, distortion product otoacoustic emissions (DPOAEs) were recorded to determine outer hair cell function at the frequency at which a persons tinnitus is matched. Results showed that (1) residual inhibition occurred more often for frequency-matched stimuli than nonfrequency-matched stimuli, (2) the mean duration of residual inhibition was not significantly higher for frequency-matched stimuli compared to nonfrequency-matched stimuli, (3) residual inhibition duration was the greatest with the longest listening duration for both frequency-matched and nonfrequency-matched stimuli, and (4) there was no evidence of absent DPAOEs in the matched-frequency region of tinnitus. An interview of the participants approximately 3 to 5 weeks after completing the study revealed that none of them actually used the residual inhibition technique employed in the present study consistently at home to gain relief from their tinnitus. Results suggest that residual inhibition provides a very temporary relief of tinnitus for some patients.

Benefits of Sound-Field Amplification for Elementary School Children With and Without Hearing Loss: A Review

Abstract Research has shown that typical classrooms are often too noisy and reverberant to provide an adequate learning environment for students (Crandell & Smaldino, 1994; Sanders, 1965). In fact, they offer a less than optimal learning environment for students with normal hearing sensitivity and an unacceptable learning environment for students suffering from a hearing loss (Crandell et al., 1995). Collectively, results of sound-field amplification research suggest significant benefits in academics, and attendstiming and learning behaviors for children with normal hearing sensitivity in elementary school. However, there is a dearth of information regarding the effects of amplification use on children with hearing loss secondary to otitis media. Future studies should expand the existing body of research by demonstrating the effects of sound-field amplification use on the classroom performance of elementary school children of varying ages with and without hearing loss secondary to middle ear pathology.