Chairperson: Andrea Kelly

Tuesday 25th June 2013

1.45pm Professor Dirk De Ridder

An integrative model of auditory phantom perception: tinnitus as a unified percept of interacting separable subnetworks

Tinnitus is a considered to be an auditory phantom phenomenon, a persistent conscious percept of a salient memory trace, externally attributed, in the absence of a sound source. It is perceived as a phenomenologically unified coherent percept, binding multiple separable clinical characteristics, such as its loudness, the sidedness, the type (pure tone, noise), the associated distress and so on. A theoretical pathophysiological framework capable of explaining all these aspects in one model is highly needed. The model must incorporate both the deafferentation based neurophysiological models and the dysfunctional noise cancelling model, and propose a ‘tinnitus core’ subnetwork. The tinnitus core can be defined as the minimal set of brain areas that needs to be jointly activated (=subnetwork) for tinnitus to be consciously perceived, devoid of its affective components. The brain areas involved in the other separable characteristics of tinnitus can be retrieved by studies on spontaneous resting state magnetic and electrical activity in people with tinnitus, evaluated for the specific aspect investigated and controlled for other factors. By combining these functional imaging studies with neuromodulation techniques some of the correlations are turned into causal relationships. Thereof, a heuristic pathophysiological framework is constructed, integrating the tinnitus perceptual core with the other tinnitus related aspects. The phenomenologically unified percept of tinnitus can be considered an emergent property of multiple, parallel, dynamically changing and partially overlapping subnetworks, each with a specific spontaneous oscillatory pattern and functional connectivity signature. Communication between these different subnetworks is proposed to occur at hubs, brain areas that are involved in multiple subnetworks simultaneously. These hubs can take part in each separable subnetwork at different frequencies. Communication between the subnetworks is proposed to occur at discrete oscillatory frequencies. As such, the brain uses multiple nonspecific networks in parallel, each with their own oscillatory signature, that adapt to the context to construct a unified percept possibly by synchronized activation integrated at hubs at discrete oscillatory frequencies.

2.30pm Giriraj Shekhawat A double blind, sham-controlled, randomised clinical trial of transcranial direct current stimulation (tDCS) and Hearing Aid for the Management of Tinnitus G.S.Shekhawat, G.D.Searchfield, C.M.Stinear Section of Audiology, School of Population Health, Tamaki Innovation Campus, University of Auckland, New Zealand.

Background/Aims –The aim of this study was to investigate the role of multi-session anodal tDCS of the Left Temporoparietal Area (LTA) in combination with hearing aid use on tinnitus. Methods - Forty participants (mean 54 years) suffering from chronic tinnitus (minimum 2 years) completed a seven month long clinical trial. Participants were randomized in to two groups (each n=20): control (sham tDCS) and experimental (tDCS: five consecutive sessions of anodal tDCS [2mA intensity and 20 minutes duration] of LTA) followed by hearing aid use for six months. The impact of tDCS and hearing aid fitting on tinnitus was measured with questionnaires (THQ, TFI, HADS, TSNS, HHI, CGI, and VAS) and Minimum Masking Levels before, immediately after the stimulation, 3rd and 6th months after hearing aid use. Results – Hearing aid use lead to a significant improvement in most outcome measures. Preliminary evidence suggests that tDCS may have reduced the time to maximum hearing aid benefit. Duration of hearing aid use correlated with degree of improvement. Conclusion – Hearing aids resulted in significant improvement in tinnitus after 3 and 6 months of use, independent of use of tDCS. Further investigations of tDCS or other neuromodulators may prove that priming the auditory system for amplification is beneficial for tinnitus and hearing outcomes. ------3.30pm Professor Ruth Bentler

Frequency compression hearing aids: Impact on speech and language development

Abstract: Signal-processing options such as nonlinear frequency compression (NLFC) have been introduced to expand the potential for communication success for adults and children with measureable hearing loss. Due to the limited bandwidth of current transducers, development of a strategy that provides access to frequencies above 6000 Hz has been encouraged by previous research (e.g., Stelmachowicz et al, 2001 & 2007). As a result, this and similar processing schemes are now the default in many hearing aids. In this study, we were able to assess speech and language outcomes for a subset of children who are participating in a large multi-site observational study of outcomes with children with hearing loss (OCHL; NIH RO1 DC009560). Subjects at ages 3, 4, and 5 comprised the data pool; half of the subjects were fitted with NLFC and half were fit with more conventional signal processing schemes. None of the demographic variables between the groups, including age of diagnosis, age of fit, use time, SES, etc., were significantly different. Results indicated no differences in speech and language outcomes for the two groups at any of the three age levels. Further research is needed to determine the likelihood of improving these critical areas of development with alternative fitting and processing schemes.

Stelmachowicz, P. G., Lewis, D. E., Choi, S., et al. (2007). Effect of stimulus bandwidth on auditory skills in normal-hearing and hearing-impaired children. Ear Hear, 28, 483-494.

Stelmachowicz, P. G., Pittman, A. L., Hoover, B. M., et al. (2001). Effect of stimulus bandwidth on the perception of /s/ in normal-and hearing-impaired children and adults. J Acoust Soc Am, 110, 2183-2190.

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4.00pm Jan Pollard, Chief Audiologist, Sonic

Clinical Applications using the Chirp Stimulus in Auditory Evoked Response Assessment

Click and Tone Burst stimuli are routinely used in ABR assessment. The development of the Chirp stimulus now provides the clinician with the ability to identify auditory responses faster and more easily. Responses are larger due to the time-based frequency spectra of the stimulus that stimulates and synchronises responses along the entire cochlea. Ongoing research into its use for the The use of a Chirp instead of routine clicks and tone bursts is beginning to be seen in clinics but also in equipment used for Automated ABR in Infant Hearing Screening programs including New Zealand.

The MB11 Beraphone uses an improved Chirp stimulus and detection algorithm. Comparative studies have shown high sensitivity and specificity for hearing loss detection. Studies have shown that this minimal consumables ( gel only) device is comparable to other commonly used devices. This presentation discusses the use of the Chirp stimulus in AEP testing and recent studies in neonatal populations.

Cebulla M, Shehatta-Dieller W. (2012) “ABR-based Newborn Hearing Screening with MB11 BERAphone using an optimized Chirp for acoustical stimulation” Int. J Pediatr. Otorinolaryngol. 76, 536- 543. van den Berg E, Deiman C, van Straatan HLM (2010) “MB 11 Beraphone hearing screening compared to ALGO portable in Dutch NICU: A Pilot Study” ” Int. J Pediatr. Otorinolaryngol. 74, 1189- 1192 Sturzebecker E, Cebulla M, Elberling C, and Berger T (2006) “New Efficient Stimuli for Evoking Frequency-specific Auditory Seady-state responses” J.Am.Acad.Audiol. 17, 448- 461

------4.30pm David Welch , University of Auckland Dunedin Longitudinal Study

The Dunedin Multidisciplinary Health and Development Study began with 1037 people born in Dunedin between April 1972 and March 1973 and has followed their lives in broad and in-depth ways through to their late 30s (so far). It is a unique study, and the people who make up the birth cohort continue to return to be tested and interviewed each assessment. The assessments combine interviews and objective measurements, and the study has information about most important aspects of life in its database. The unusual nature of the study has allowed interesting questions about ears and hearing to be answered. Findings relating to hearing have been based mostly on otological and audiological assessments performed throughout childhood. These findings were influential in developing understanding of the epidemiology of Otitis Media with Effusion. Later hearing research from the study has looked at psychosocial and developmental factors associated with natural variation in normal sensorineural hearing, and investigated associations between adult tinnitus with childhood hearing, and with personality.