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  1. Evaluating speech detection in aided infants and estimating pure tone thresholds in unresponsive adults: Auditory-evoked cortical potentials Harvey Dillon, Bram Van Dun, Lyndal Carter, Kirsty Gardner-Berry HEARing CRC National Acoustic Laboratories (NAL) ASA, Audiology Now! With thanks to John Seymour, Suzanne Purdy, Maryanne Golding www.hearingcrc.org NAL: Dillon, Van Dun, Carter, Gardner-Berry

  2. The need for a new measurement tool NAL: Dillon, Van Dun, Carter, Gardner-Berry

  3. Cochlear implant needed Confirmation of fitting Fine-tuning needed Evaluation of aided functioning in infants Universal new born screening Early fitting of hearing aids Need for an evaluation method NAL: Dillon, Van Dun, Carter, Gardner-Berry

  4. So baby, how does it sound? Objective hearing aid evaluation for: • young infants • difficult-to-test people NAL: Dillon, Van Dun, Carter, Gardner-Berry

  5. Why the rush?Language ability 6 months after implantation NAL: Dillon, Van Dun, Carter, Gardner-Berry

  6. Early intervention leads to better language development at 6 months after fitting (n=90) Significant effect of age of fitting: p = 0.001* NAL: Dillon, Van Dun, Carter, Gardner-Berry

  7. Early intervention leads to better language development at 6 months after fitting (n=90) Significant effect of age of fitting: p = 0.001* NAL: Dillon, Van Dun, Carter, Gardner-Berry

  8. Why use cortical responses? NAL: Dillon, Van Dun, Carter, Gardner-Berry

  9. Why cortical responses to evaluate hearing aid fitting in infants? • Reliably present in awake young infants • More likely to correlate well with perception • Can be elicited by a range of speech phonemes – close to desired outcomes • Stimuli handled reasonably by hearing aids • Can be very frequency specific if needed NAL: Dillon, Van Dun, Carter, Gardner-Berry

  10. Cortical responses – Where from Development with age Typical waveforms Measuring infant cortical responses – video Research results Effect of auditory experience Cortical responses to different stimuli Automatic detection of cortical responses Sensation level, hearing loss, and noise Relationship to functional hearing ability Clinical applications Estimating hearing thresholds in adults – live demo Assessing speech audibility for infants Case studies Future possibilities Overview of Learning Lab NAL: Dillon, Van Dun, Carter, Gardner-Berry

  11. FUNDAMENTALS OF CORTICAL RESPONSES NAL: Dillon, Van Dun, Carter, Gardner-Berry

  12. Corpus callosum Plastic, e.g following cochlear ablation Cortex: Complex detection Perception Medial geniculate nucleus Thalamus: Auditory and visual map integrated, relayed to cortex SC: Visual spatial map IC: Form full spatial map, Parallel processing paths join, History dependent Lateral lemnisci VNLL: Fed by contralateral CN Sorting, comparing and categorizing MSO: Detect interaural time LSO: Detect interaural level AVCN: Frequency analysis, PVCN: Timing well preserved DCN: Inhibitory circuits, pinna cue detection? Parallel processing Needs to be fed to develop & maintain NAL: Dillon, Van Dun, Carter, Gardner-Berry

  13. Corpus callosum Plastic, e.g following cochlear ablation Cortex: Complex detection Perception Medial geniculate nucleus Thalamus: Auditory and visual map integrated, relayed to cortex SC: Visual spatial map IC: Form full spatial map, Parallel processing paths join, History dependent Lateral lemnisci VNLL: Fed by contralateral CN Sorting, comparing and categorizing MSO: Detect interaural time LSO: Detect interaural level AVCN: Frequency analysis, PVCN: Timing well preserved DCN: Inhibitory circuits, pinna cue detection? Parallel processing Needs to be fed to develop & maintain NAL: Dillon, Van Dun, Carter, Gardner-Berry

  14. The end of the road NAL: Dillon, Van Dun, Carter, Gardner-Berry

  15. Auditory cortex orientation NAL: Dillon, Van Dun, Carter, Gardner-Berry

  16. Auditory cortex orientation NAL: Dillon, Van Dun, Carter, Gardner-Berry

  17. Auditory cortex orientation NAL: Dillon, Van Dun, Carter, Gardner-Berry

  18. - + + Hudson, 2009 NAL: Dillon, Van Dun, Carter, Gardner-Berry

  19. Auditory cortex and current sources Sussman et al (2008) NAL: Dillon, Van Dun, Carter, Gardner-Berry

  20. Cortical responses in adults with normal hearing NAL: Dillon, Van Dun, Carter, Gardner-Berry

  21. P2 N1 5.0 P1 2.5 µV 0.0 -2.5 100 200 300 400 600 0 500 Adult NAL: Dillon, Van Dun, Carter, Gardner-Berry

  22. Adult grand mean waveforms at Cz Speech Tones NAL: Dillon, Van Dun, Carter, Gardner-Berry

  23. Development of cortical responses with age NAL: Dillon, Van Dun, Carter, Gardner-Berry

  24. Infants P 10 µV 5 N 0 -5 -100 0 100 200 300 400 500 600 ms NAL: Dillon, Van Dun, Carter, Gardner-Berry

  25. Maturational effects on cortical evoked response morphology Ponton et al (2000) • N=8-16 per grand mean • Cz site • stimulus = 10 click train, 2 ms ISI @ 65 dB SL • rate = 1.3/s NAL: Dillon, Van Dun, Carter, Gardner-Berry

  26. 2 years 12 years I  II Fewer neuro-filaments in young children, especially in more superficial cortical layers thought to generate N1 (Ponton, Moore & Eggermont 1999) III IV V Axonal neuro- filaments Axonal neuro- filaments VI Cell bodies Cell bodies NAL: Dillon, Van Dun, Carter, Gardner-Berry

  27. NAL data Sharma et al Latency versus age NAL: Dillon, Van Dun, Carter, Gardner-Berry

  28. MEASURING CORTICAL RESPONSES NAL: Dillon, Van Dun, Carter, Gardner-Berry

  29. Practical demonstration (by video):speech sounds and infants Set-up – equipment diagram Video of infant being tested NAL: Dillon, Van Dun, Carter, Gardner-Berry

  30. Practical implementation of cortical testing: HearLab Disclosure: NAL will get a royalty for each unit sold. Thank you: The HearLab development team – Teck Loi, Barry Clinch, Isabella Tan, Ben Rudzyn, Lyndal Carter, Dan Zhou, Scott Brewer NAL: Dillon, Van Dun, Carter, Gardner-Berry

  31. NAL: Dillon, Van Dun, Carter, Gardner-Berry

  32. Equipment configuration NAL: Dillon, Van Dun, Carter, Gardner-Berry

  33. CAEP room set-up at the National Acoustic Laboratories Baby sits on parent’s lap in the centre of the room or in a high chair. Free Field Speaker NAL: Dillon, Van Dun, Carter, Gardner-Berry

  34. Electrode equipment NAL: Dillon, Van Dun, Carter, Gardner-Berry

  35. Videos Attaching electrodes 01:00 2.30  end Headband usage Putting in hearing aids Keeping alert carousel NAL: Dillon, Van Dun, Carter, Gardner-Berry

  36. NAL: Dillon, Van Dun, Carter, Gardner-Berry

  37. Keeping electrodes on the baby using a headband NAL: Dillon, Van Dun, Carter, Gardner-Berry

  38. Keeping the baby awake! NAL: Dillon, Van Dun, Carter, Gardner-Berry

  39. Tools for keeping baby quiet, alert, awake NAL: Dillon, Van Dun, Carter, Gardner-Berry

  40. (More) tools for keeping baby quiet, alert, awake NAL: Dillon, Van Dun, Carter, Gardner-Berry

  41. (Yet more) tools for keeping baby quiet, alert, awake NAL: Dillon, Van Dun, Carter, Gardner-Berry

  42. Practical issues in measurement Averaging Electrode location Artefact rejection Filtering Number of runs Head support Interference – lighting, mobile phones, active electrodes NAL: Dillon, Van Dun, Carter, Gardner-Berry

  43. Averaging NAL: Dillon, Van Dun, Carter, Gardner-Berry

  44. Electrode location Non-inverting + - Inverting Ground NAL: Dillon, Van Dun, Carter, Gardner-Berry

  45. Artefact rejection Peak voltage > 150 µV Rms voltage Insufficient voltage NAL: Dillon, Van Dun, Carter, Gardner-Berry

  46. Filtering NAL: Dillon, Van Dun, Carter, Gardner-Berry

  47. Head support Yes!! NAL: Dillon, Van Dun, Carter, Gardner-Berry

  48. Reducing measurement variability(random electrical signals)  Speeding up measurements Increasing validity of interpretation NAL: Dillon, Van Dun, Carter, Gardner-Berry

  49. Active electrodes NAL: Dillon, Van Dun, Carter, Gardner-Berry

  50. Capacitive Coupling 50 Hz Passive Electrodes NAL: Dillon, Van Dun, Carter, Gardner-Berry