Medical Bionics - Research Publications

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Type: Journal Article × Author: McKay, Colette × Author: Henshall, Katherine ×

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    Intensity Discrimination and Speech Recognition of Cochlear Implant Users
    McKay, CM ; Rickard, N ; Henshall, K (SPRINGER, 2018-10)
    The relation between speech recognition and within-channel or across-channel (i.e., spectral tilt) intensity discrimination was measured in nine CI users (11 ears). Within-channel intensity difference limens (IDLs) were measured at four electrode locations across the electrode array. Spectral tilt difference limens were measured with (XIDL-J) and without (XIDL) level jitter. Only three subjects could perform the XIDL-J task with the amount of jitter required to limit use of within-channel cues. XIDLs (normalized to %DR) were correlated with speech recognition (r = 0.67, P = 0.019) and were highly correlated with IDLs. XIDLs were on average nearly 3 times larger than IDLs and did not vary consistently with the spatial separation of the two component electrodes. The overall pattern of results was consistent with a common underlying subject-dependent limitation in the two difference limen tasks, hypothesized to be perceptual variance (how the perception of a sound differs on different presentations), which may also underlie the correlation of XIDLs with speech recognition. Evidence that spectral tilt discrimination is more important for speech recognition than within-channel intensity discrimination was not unequivocally shown in this study. However, the results tended to support this proposition, with XIDLs more correlated with speech performance than IDLs, and the ratio XIDL/IDL also being correlated with speech recognition. If supported by further research, the importance of perceptual variance as a limiting factor in speech understanding for CI users has important implications for efforts to improve outcomes for those with poor speech recognition.
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    Interhemispheric EEG coherence is reduced in auditory cortical regions in schizophrenia patients with auditory hallucinations
    Henshall, KR ; Sergejew, AA ; Rance, G ; McKay, CM ; Copolov, DL (ELSEVIER SCIENCE BV, 2013-07)
    Central auditory processing has been reported to be impaired in schizophrenia patients who experience auditory hallucinations, and interhemispheric transfer in auditory circuits may be compromised. In this study, we used EEG spectral coherence to examine interhemispheric connectivity between cortical areas known to be important in the processing of auditory information. Coherence was compared across three subject groups: schizophrenia patients with a recent history of auditory hallucinations (AH), schizophrenia patients who did not experience auditory hallucinations (nonAH), and healthy controls (HC). Subjects listened to pure tone and word stimuli while EEG was recorded continuously. Upper alpha and upper beta band coherence was calculated from six pairs of electrodes located over homologous auditory areas in the left and right cerebral hemispheres. Significant between-group differences were found on four electrode pairs (C3-C4, C5-C6, Ft7-Ft8 and Cp5-Cp6) in the upper alpha band. Relative to both the HC and nonAH groups, coherence was lower in the AH patients, consistent with the hypothesis that interhemispheric connectivity is reduced in these patients.