On the Relationship Between Noise and Speech Recognition in Cochlear Implant Subjects: A Theoretical

One factor that may impede speech recognition by cochlear implant subjects is that electricall y stimulated nerves respond with a much higher level of synchrony than what is normally observed in acoustically stimulated nerves. Thus, the response patterns “seen” at higher processing centers are substantially different from those generated under normal acoustic stimulation. These differences may form the basis for a degradation of speech understanding since the patterns generated under electrical stimulation may be interpreted incorrectly by higher processing centers. Recent data from the implant research community has suggested that high rates of stimulation [1], addition of low levels of noise to the electrical stimulus [2-5], or elevated levels of “ internal noise” [6] may provide some implanted individuals with improved speech recognition. In this paper, we present theoretical data that indicate that the addition of noise may provide improved neural responses to electrical stimulation along with psychophysical data that may indicate that individuals with higher levels of internal noise do in fact have higher levels of speech recognition.

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