Proefschrift_vd_Beek

In some cases the highest current level indeed produced the widest curves. In Figure 4, B, an example of an individual patient is shown for the middle electrode. For this individual patient the SOE is wider for the highest current level compared to the lower current levels. However, across all subjects the second linear mixed model showed that the curve widths of the medium and high intensity were not significantly different from those found at the low intensity ( p = 0.5, and p = 0.8 respectively). Recording electrode The third linear mixed model with data of fi ve subjects (summa-rized in Table 4) revealed signifi cant effects of the recording site on the width of the selectivity measures. Generally, the curves tended to shift in the direction of the recording electrode. For the apical electrode (EA-B) the width was 1.5 contact spacing smaller when measured apically compared to basally, and for the basal electrode (EB-A) the width was 1.7 contacts wider when measured apically. The results from the electrode in the middle of the array (EM) did not show signifi cant differences between the recording contacts.

Parameter Manipulations in SOE (eCAP)

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Figure 4. A: Curves showing normalized eCAP amplitudes obtained using scanning (solid symbols) and selectivity measures (open symbols) in one representative subject. B: Selectivity curves at the middle electrode position for three current levels (Low: dotted line; Medium: dashed line; High: solid line). C: Selectivity curves in one representative subject with masker electrode fixed (circles) and probe fixed (diamonds) at the three current intensities (Low: dotted line; Medium: dashed line; High: solid line). Note that the eCAP amplitude is not normalized in C in order to illustrate level effects on the eCAP amplitude. D: Scanning curves obtained using the forward masking (plus sign) and alternating polarity (square) artefact rejection scheme at High (solid lines) and Medium (dashed lines) intensities. Figure 4. A: Curves showing normalized eCAP amplitudes obtained using scanning (solid symbols) and selectivity measures (open symbols) in one representative subject. B: Selectivity curves at the middle electrode position for three current levels (Low: dotted line; Medium: dashed line; High: solid line). C: Selectivity curves in one representative subject with masker electrode fixed (circles) and probe fixed (diamonds) at the three current intensities (Low: dotted line; Medium: dashed line; High: solid line). Note that the eCAP amplitude is not normalized in C in order to illustrate level effects on the eCAP amplitude. D: Scanning curves obtained using the forward masking (plus sign) and alternating polarity (square) artefact rejection scheme at High (solid lines) and Medium (dashed lines) intensities.

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some subjects showing large changes in curve width with changing stimulus level.

the low and the high current level in almost all patients. Informal inspection of the data in Figure 3 suggests that while there was a