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MEG system for Cochlear Implant Recipients and Auditory Entrainment
Qingqing Meng1,3,4, Catherine McMahon2,3,4 and Blake J...
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MEG system for cochlear implants ecipients and auditory entrainment - HEARing CRC PhD presentation

The use of a custom-engineered MEG system, in combination with noise reduction techniques to measure speech processing in the brains of cochlear implant recipients.

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MEG system for cochlear implants ecipients and auditory entrainment - HEARing CRC PhD presentation

  1. 1. MEG system for Cochlear Implant Recipients and Auditory Entrainment Qingqing Meng1,3,4, Catherine McMahon2,3,4 and Blake Johnson1,3,4 1 Macquarie University, Department of Cognitive Science, 2 Macquarie University, Department of Linguistics 3 The HEARing Cooperative Research Centre 4 ARC Centre of Excellence in Cognition and its Disorders Introduction A novel MEG system, customized to measure brain function of cochlear implant recipients is in a second iteration of its design phase. Two groups of irregular baseline 2nd order gradiometers have been installed to reduce the effects of electromagnetic artefacts produced by the cochlear implant device. Speech entrainment, characterized by oscillatory activities in auditory cortex (theta band) phase-locked to slow varying speech temporal envelope, has been proposed to index speech processing [1] and may underlie speech perception performance of cochlear implant recipients. Here, we review the MEG design improvements and present methods for evaluating amplitude envelope entrainment as a measure of speech processing in the cortex of cochlear implant recipients. creating sound value www.hearingcrc.org Upgraded MEG System Type A sensor: Measures environmental noise, has null or near- null responsiveness at locations corresponding to auditory cortex. Type B sensor: Measures auditory cortical activity, has null or near-null responsiveness at locations corresponding to the cochlear implant. Conclusions The custom-engineered MEG system, in combination with noise reduction techniques, will be used to measure speech processing in the brains of cochlear implant recipients. Speech processing will be indexed by spectral coherence with the temporal envelope of the speech signal. Methods for measuring speech processing in the brain Speech entrainment is indexed by the spectral coherence between brain recordings and the temporal envelope of speech [3]. EEG coherence with 6 Hz amplitude modulated white noise is shown. 12 type A and 20 type B irregular baseline 2nd order gradiometers are contained in a cylindrical dewar. It covers one side of a participant’s head contralateral to a (unilateral) cochlear implant. MEG System Evaluation Auditory cortical activity was acquired with normal hearing participants and a cochlear implant simulator. Result with CALM noise reduction technique [2] reveals capability of suppressing interference introduced by cochlear implant. References [1] Nai Ding and Jonathan Z Simon. Cortical entrainment to continuous speech: functional roles and interpretations. Front Human Neurosci, 8, 2014. [2] Y Adachi, M Shimogawara, M Higuchi, Y Haruta, and M Ochiai. Reduction of non-periodic environmental magnetic noise in meg measurement by continuously adjusted least squares method. IEEE Trans Appl Supercond, 11(1):669-672, 2001. [3] Jonathan E Peelle, Joachim Gross, and Matthew H Davis. Phase-locked responses to speech in human auditory cortex are enhanced during comprehension. Cerebral Cortex, 23:1378-1387, 2013.

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