AHH seminar: Debi Vickers & John Deeks

Speakers: Professor Associate Professor Debi Vickers & John Deeks
Date: Thursday 16 November
Time: 10.00am – 12.30pm
Location: Australian Hearing Hub, Level 1, Lecture Theatre 

10.00am – 10.05am – Welcome
10.05am – 10.45am – Optimizing outcomes for hearing impaired listeners – Debi Vickers
10.45am – 11.00am – Q & A
11.00am – 11.45am – Temporal pitch perception by cochlear implant users – John Deeks
11.45am – 12.00pm – Q & A
12.00pm – 12.30pm – Light lunch & Networking
Please see below the abstracts and biographies 

Who should come:  hearing, speech and language researchers and clinicians, cochlear implant researchers and clinicians, cognitive scientists, psychologists, people interested in objective measures, paediatric deafness and speech perception.
Learn from one another and see what collaboration opportunities are available.
Entry is free and open to the public.
Please register by Monday 13 November 2017 to louise.dodd@mq.edu.au

Funding acknowledgements: John Deeks trip has been funded by a Macquarie University Visiting Fellow grant and Debi Vickers trip has been funded by the Cochlear Macquarie University Partnership.


Optimizing outcomes for hearing impaired listeners – Debi Vickers

This research is concerned with interventions and assessments that can support optimization of speech perception outcomes for hearing-impaired listeners.
The first study concerns the detection of hearing problems in babies, and looked at the impact of introducing the measurement of cortical responses, using HearLab, into the newborn hearing screening pathway. A retrospective analysis of two consecutive cohorts (2008-2011 and 2011-2015) was conducted. The first cohort was prior to the introduction of cortical measurements and the second cohort underwent the cortical measurement protocol as part of their audiological management. This showed that the introduction of HearLab resulted in an earlier average hearing aid fitting age for babies with mild-moderate losses. When reviewing the reasons it showed that the use of unaided and aided cortical measurements for speech sounds helped parents to have a better understanding of the speech detection abilities of their children and also it gave audiologists greater confidence for prescribing hearing aids.
The second study examined development of cortical responses to sound following cochlear implant activation, using the electrically evoked auditory change complex (eACC). A significant relationship was found between the emergence of the eACC to changes in electrode stimulation, behavioural electrode discrimination and speech understanding. Such a measure could be helpful in informing clinical fitting and training interventions, particularly important for adults with early onset of deafness and late implantation.
The final study developed and assessed a spatial speech in noise measure for evaluating ‘real-world’ hearing with bilateral cochlear implants using a more challenging assessment than currently used clinically. The ‘spatial speech test’ was developed to simultaneously assess speech perception and the perception of relative location of a target sound in the presence of noise. We have shown with our latest implementation that bilateral cochlear implant users were able to perform above chance in both speech perception and relative localization judgements in the presence of noise, although they did not demonstrate spatial release from masking they demonstrated benefit from the second side implant for relative localization judgements.

Debi Vickers is an Associate Professor of Speech and Hearing Sciences at University College London (UCL). Her doctoral work looked at optimizing the delivery of fricatives in hearing aids for profoundly deaf adults and her post-doctoral research was in psychophysics, speech perception and dead regions, based in the Hearing Laboratory at the University of Cambridge. The majority of her research over the past decade at UCL has looked at optimizing outcomes for cochlear implant users, more recently focusing on electrode selection, plasticity, training and bilateral implants. Debi is a sub-theme (‘Transforming Hearing Devices’) lead for the UCL Biomedical Research Centre in Deafness.

Current projects in her research group look at ‘brain changes following implantation’, ‘maximising binaural processing’, ‘optimising cochlear implant fitting parameters’, ‘music training to improve listening skills’, ‘the development of real-life listening assessments’, ‘candidacy criteria for cochlear implants’, ‘maximizing outcomes for babies and infants with hearing impairment’ and ‘the impact of classroom acoustics on speech understanding’.


Temporal pitch perception by cochlear implant users – John Deeks
Cochlear implant (CI) users can derive a musical pitch from the temporal pattern of pulses delivered to one or more electrodes. However, this temporal pitch perception deteriorates with increasing pulse rate, and most listeners cannot detect increases in pulse rate beyond about 300 pps. This upper limit differs markedly between CI users, and between different electrodes within the same user, suggesting a peripheral origin to the limit. But, the upper limit is immune to several manipulations that we expect to substantially alter the pattern of neural firing on auditory nerve (AN) fibres. Three studies are described, aimed at further understanding the neural basis of temporal pitch processing in CI users. In the first, we measured rate discrimination and AN activity (using the electrically evoked compound action potential (ECAP)) in the same subjects and with the same stimuli. Results show that important aspects of temporal pitch perception cannot be explained in terms of the AN response, at least as measured by ECAPs. In the second, we investigated whether the upper limit increased in CI users following activation of their implant. We tested CI users on the day of activation (“switch on”) and at two and six months later. The upper limit increased significantly between but not within sessions. Performance on a low-rate discrimination task improved significantly between sessions, but the effect size was significantly less than for the upper limit. Findings are consistent with an effect of neural plasticity on temporal coding at high rates. Lastly, we report results of a double-blind placebo-controlled trial of a drug, AUT0063, on three temporal processing tasks in CI users. Kv3.1 is a fast acting potassium channel important for returning the cell membrane to a resting state, allowing the neuron to fire in a sustained and temporally accurate manner in response to high-rate pulse trains. Kv3.1a channels are susceptible to auditory deprivation, the effects of which can be partially reversed in animal models using AUT0063. Despite good test-re-test reliability (correlations of at least 0.89), no effect of the drug was found.

John Deeks, PhD is a Senior Research Scientist at the MRC Cognition and Brain Sciences Unit, University of Cambridge. His research focuses on hearing mechanisms in both normal-hearing listeners and people fit with a cochlear implant. In Cambridge, he is part of the Speech and Hearing Group, headed by Bob Carlyon. He obtained a BSc in Experimental Psychology from the University of Sussex, an MSc in Audiology from the University of Southampton, and PhD – concerned with pitch and timbre perception by profoundly hearing impaired listeners – from the Department of Phonetics and Linguistics, UCL.