AUDIOLOGY & SLP MATERIALs

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STIMULUS FACTORS:   AP latency decreases and amplitude increases as stimulus intensity is increased. Ø    SP is not observed at lower intensity level  (< 60 dBPESPL) Ø    Monophasic stimulus polarity produces a CM component and it produces latency difference in the SP and AP components Ø    Increasing stimulus rate reduces AP amplitude where as the SP characteristics remain unchanged. Ø    ECochG  morphology changes dramatically for click Vs TB stimuli and also for low Vs high frequency tone burst stimuli. ECochG electrode problems:-             ECochG activity arising from the cochlea and distal eighth nerve is best measured with a near field technique.  Response amplitude and reliability increases substantially as the recording electrode approaches the cochlea, which serves to overcome various clinical measurement prolem. Effect of electrode location on ECochG:-             With an electrode array consisting of a non inverting electrode on

HISTORICAL PERSPECTIVE In contrast to the rather confusing and varied terminology used to describe other AERs, there is relative consistency in referring to this response. Very early papers refer to ”cochlear potentials” and some researchers use the terms “cochlear action potentials” or “cochlear microphonic” potentials. However, most authors and clinicians adhere to the conventional term “electrocochleography” or “electrocochleogram,” as abbreviated ECochG or ECoG. The former abbreviation is possibly more precise, since ECoG may also refer to “electrocorticogram,” an EEG-type recording. Along the same line, the abbreviation “ECG” is not advised because it is also an abbreviation of a diagnostic measure of heart function, the “electrocardiogram.” In this book, therefore, the term electrocochleography, abbreviated ECochG, is used exclusively. Typical ECochG waveforms were shown in Figure 1.1. The response, arising from the cochlea and eighth (auditory)