Monday 24 June am
Chair: Ingrid Dekker
9.00am Professor Dirk De Ridder
Phantom Perceptions
Bio-DIRKDE RIDDER
The 2013 conference committee is pleased to announce that Prof Dirk De Ridder has also agreed to attend as a guest speaker. Prof De Ridder is a neurosurgeon and currently holds the position of visiting professor at the Department of Neurosurgery, University Hospital Antwerp, Belgium. He is the author or co-author of over 140 academic publications as well as sitting on the review board for a number of prominent journals. Prof De Ridder is a founder and director of the Tinnitus Research Initiative and one of his primary interests is in surgical treatment of tinnitus. He was the first person to surgically implant an electrode into the auditory cortex for treatment of chronic tinnitus. From February 2013 Prof De Ridder will take up the newly created position of Neurological Foundation Chair of Neurosurgery at OtagoUniversity.
2. Phantom Perceptions
Phantom perceptions arise almost universally in people who sustain sensory deafferentation, and in multiple sensory domains. The question arises ‘why’ the brain creates these false percepts in the absence of an external stimulus ?
An explanation can be provided by the Bayesian brain model. The Bayesian brain can be conceptualized as a probability machine that constantly makes predictions about the world and then updates them based on what it receives from the senses.
The brain’s main function is to reduce environmental uncertainty, as posited by the free-energy principle, which has been proposed as a universal principle governing adaptive brain function and structure.
The free-energy principle states that the brain must minimize its Shannonian (informational) free-energy, i.e. must reduce by the process of perception itsuncertainty (its prediction errors) about its environment. As completely predictable stimuli do not reduce uncertainty, they are not worthwhile of conscious processing. Unpredictable things on the other hand are not to be ignored, because it is crucial to experience them to update our understanding of the environment.
Deafferentation leads to topographically restricted prediction errors based on temporal or spatial incongruity. This leads to an increase in topographically restricted uncertainty, which should be adaptively addressed by plastic repair mechanisms in the respective sensory cortex, or via (para)hippocampal involvement if the sensory cortex plasticity changes cannot provide the missing input.
Neuroanatomically, filling in as a compensation for missing information also activates the anterior cingulate and insula, areas also involved in salience, stress and essential for stimulus detection. Associated with sensory cortex hyperactivity and decreased inhibition or map plasticity this will result in the perception of the false information created by the deafferented sensory areas, as a way to reduce increased topographically restricted uncertainty associated with the deafferentation.
In conclusion, the Bayesian updating of knowledge via active sensory exploration of the environment, driven by the Shannonian free-energy principle, provides an explanation for the generation of phantom percepts, as a way to reduce uncertainty, to make sense of the world.
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PLEASE NOTE CHANGE FROM
9.40am Moira McLeod
New Born Hearing Screening Programme Update
APOLOGIES
9.40am Jan Pollard
NEED TO CONFIRM WHICH TALK SHE IS DOING
Verifying Hearing Aid Output- Is there a right way?
Jan Pollard (Presenter)
Chief Audiologist
Sonic
The ability to use more complex stimuli in the verification of modern hearing aids has provided greater insight into their performance. Real Ear Insertion Gain was developed in the late sixties for use with analog aids with few adaptive features. There is still a place for its use in today’s clincics. However, current hearing aids have highly adaptive feature and program sets and provide the user with better outcomes in a variety of noise environments. Measuring hearing aid performance using speech (Speech Mapping), which is what the user is listening to, allows us to view the abilities of the compressors to cope with highly modulated and varying inputs. Multiple adaptive features interact with each other and effect output. Further developments such as Percentile Analysis provide us with a more three-dimensional view of the processed signal rather than a single intensity (LTASS) measure. The flexibility of using a real-time analysis process in output measurement allows for a more comprehensive view of output. Counselling avenues through the use of Live Speech Mapping also has its place in the fitting process. This presentation reviews each of the methods and how each fits together in the clincian’s repertoire of the fitting and verification process.
Clinical Applications Using the Chirp Stimulus in Auditory Evoked Response Assessment
30 Mins
Jan Pollard (Presenter)
Chief Audiologist
Sonic
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
30 mins
10.30am Morning Tea & Trade Display Viewing Time
11.00am Professor Louise Hickson
Evidence-Based Practice in Audiology: Rehabilitation Outcomes for Adults with Hearing Impairment
Bio-LOUISE HICKSON
Louise Hickson is Professor of Audiology and Head of the School of Health and Rehabilitation Sciences at The University of Queensland. She is also Co-Director of the Communication Disability Centre at that University. Prof Hickson has published over 170 research articles, books and book chapters with her main focus on the effects of hearing impairment on the lives of older people, how to measure outcomes in that population and the development of strategies and interventions that improve the uptake and outcomes of audiological rehabilitation. She is an elected Fellow and President of the International Collegium of Rehabilitative Audiology and a Fellow of the Audiological Society of Australia.
Evidence-based practice in audiology: Rehabilitation Options for Adults with Hearing Impairment
Prof Louise Hickson, Communication Disability Centre, School of Health and Rehabilitation Sciences
The University of Queensland, Australia
Hearing impairment has pervasive negative effects on the communication and quality of life of people with the impairment and on those around them. Adults with hearing impairment have a number of options that they can pursue to alleviate these negative effects and, in the current era of evidence-based practice (EBP), it is argued that shared decision making is essential so that patients can make an informed choice based on the evidence. This presentation will begin with an overview of the 5 steps in the EBP process: 1) Ask a question, 2) Access the information, 3) Appraise the articles, 4) Apply the information, and 5) Audit the outcomes. Secondly, a summary of the evidence about two of the most common intervention options for this population (hearing aid fitting and communication programs) will be presented. Finally, research that has examined the choices made by 153 new adult patients when presented with these options using a tool that helps facilitate shared decision making (i.e., a decision aid) will be outlined. Almost half (46%) of the patients opted for hearing aid fitting, 18% for communication programs and 18% chose to take no action at this point in time. The implications of these findings for hearing rehabilitation programs for adults will be discussed.
Timing: 30 - 45 minutes
11.30am Professor Suzanne Purdy
Is a Quiet Brain or a Busy Brain More Efficient at Hearing Quiet Stimuli?
Is a quiet brain or a busy brain more efficient at hearing quiet stimuli?
Suzanne C Purdy1, Susan Pockett1 and Barry Brennan2
School of Psychology1 and Department of Physics2, University of Auckland.
Audiologists spend their days asking people to respond when they detect very soft sounds and generally pay little heed to the processes that underlie this task. The characteristics of ongoing EEG alpha waves in the period immediately before a visual stimulus have been reported to affect whether or not the stimulus is consciously detected. However, different groups report opposite results. Most say more alpha predicts less detection[1-6]. One says more alpha predicts more detection[7]. We compare the characteristics of ongoing alpha during the 500 ms before threshold-strength auditory stimuli that are detected or not detected by normal adult participants.
The main finding is that different participants produce opposite results. Some people have significantly lower alpha power at central and parietal electrodes before stimuli that are heard than stimuli that are not heard. Others have significantly higher alpha power at electrodes in the same region before stimuli that are heard than stimuli that are not heard. Non-directive questioning after the experiment reveals that participants in whom lower alpha power predicted stimulus detection had adopted a strategy of clearing their mind and listening for clicks. Those in whom higher alpha power predicted stimulus detection had adopted a strategy of actively keeping the memory of a click in mind and comparing their ongoing auditory experience with that memory. Thus the answer to the question in the title apparently depends on the individual subject’s habitual thinking style.
These data from a normal population may be relevant to studies investigating causes of auditory processing disorder.
[1] T. Ergonglu, T. Demiralp, Z.Bayraktaroglu, M. Ergen, H. Beydagi, Y. Uresin, Alpha rhythm of the EEG modulates visual detection performance in humans, Brain Res. Cogn. Brain Res. 20 (2004) 376-383.
[2] G.Thut, A. Neitzel, S.A.Brandt, A. Pascual-Leone, Alpha-band electroencephalographic activity over occipital cortex indexes visuospatial attention bias and predicts visual target detection, J.Neurosci. 26 (2006) 9494-9502.
New[3] S. Hanslmayr, A. Aslan, T. Staudigl, W. Klimesch, C.S. Herrman, K.H. Bäuml, Prestimulus oscillations predict visual perception performance between and within subjects, Neuroimage 37 (2007) 1465-1473.
[4] V. Romei, V. Brodbeck, C. Michel, A. Amedi, A. Pascual-Leone, G. Thut, Spontaneous fluctuations in posterior alpha-band EEG activity reflect variability in excitability of human visual areas, Cereb. Cortex 18 (2008) 2012-2018.
[5] H. van Dijk, J.M. Schoffelen, R. Oostenveld, O. Jensen, Prestimulus oscillatory activity in the alpha band predicts visual discrimination ability, J. Neurosci. 28 (2008) 1816-1823.
[6] A.N. Busch, J. Dubois, R. VanRullen, The phase of ongoing EEG oscillations predicts visual perception, J. Neurosci. 29 (2009) 7869-7876.
[7] C. Babiloni, F. Vecchio, A. Bultrini, G.L. Romani, P.M. Rossini, Pre- and poststimulus alpha rhythms are related to conscious visual perception: a high-resolution EEG study, Cereb. Cortex 16 (2006) 1690-1700.
15 mins
11.45am Sue Pockett
Is Prefrontal Cortex a Necessary Part of the Auditory NCC?
Is prefrontal cortex a necessary part of the auditory NCC ?
Susan Pockett1, Suzanne C Purdy1 and Barry Brennan2
School of Psychology1 and Department of Physics2 University of Auckland
Several existing theories of consciousness suggest that neural activity in the prefrontal cortex is a crucial part of the neural correlate of consciousness (NCC) for sensations[1-4]. We investigate this hypothesis by comparing ERPs evoked by threshold-strength click stimuli that are heard with ERPs evoked by objectively identical stimuli that are not heard. Superficially, our data appear strongly to confirm the hypothesis. Stimuli that are heard evoke large ERPs over the prefrontal cortex, while stimuli that are not heard do not.
However, there are several possible confounds in these data. For the experimenter to know which threshold-strength stimuli are heard and which not, participants must press one of two buttons in response to a question displayed on a screen at a random time after each stimulus. When the requirements to (1) voluntarily attend to the stimuli, (2) decide whether or not a click was heard and (3) press a button to report this decision are removed (by turning up the stimulus strength to a point where all stimuli are heard and asking the participant not to attend or respond) most if not all of the ERP activity recorded over prefrontal regions disappears. In part because of the intrinsic limitations of scalp EEG, questions about whether all prefrontal activity disappears and whether any that remains is related to conscious click perception or some other factor remain open to debate. ECoG recordings, which are not contaminated by either scalp muscle activity or spatial blurring due to remote recording, may help resolve the issue.
[1] Dehaene, S. Naccache, L. Towards a cognitive neuroscience of consciousness: basic evidence and a workspace framework, Cognition 79 (2001) 1-37.
[2] Crick, F. and Koch, C.,A framework for consciousness. Nat. Neurosci. 6, (2003) 119–126
[3] Lau, H.C., Passingham, R.E., Relative blindsight in normal observers and the neural correlate of visual consciousness. Proc. Natl. Acad. Sci. U.S.A. 103, (2006) 18763–18768.
[4] Dehaene, S., Changeux, J.P., Experimental and theoretical approaches to conscious processing. Neuron 70 (2011), 200–227.
15 Mins
12.00pm Melissa Baily
Update from Accessable Hearing Advisor about Funding Criteria
Update from accessable Hearing Advisor about funding criteria
Melissa Baily MNZAS
Professional Advisor- Hearing, accessable
This talk will present an overview of Ministry of Health eligibility criteria for hearing aid funding, subsidies and repairs, including recent criteria clarification, and guidelines for making applications for accessories and FM systems. It will also provide a summary of some interesting facts and figures about the services provided since it commenced 1 July 2011. There will also be a presentation about making applications online with accessable’s Online Catalogue Ordering system (OCO).
45-60 minutes
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12.30pm Lunch & Trade Display Viewing Time