Limits...
Extending the limits of place and temporal pitch perception in cochlear implant users.

Macherey O, Deeks JM, Carlyon RP - J. Assoc. Res. Otolaryngol. (2010)

Bottom Line: A series of experiments investigated the effects of asymmetric current waveforms on the perception of place and temporal pitch cues.For PSA pulses presented to apical electrodes, the upper limit of temporal pitch was significantly higher than that for all the other conditions, averaging 713 pps.However, a multidimensional scaling study showed that the percept associated with a rate change, even at high rates, was orthogonal to that of a place change and therefore reflected a genuine change in the temporal pattern of neural activity.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council, Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge, UK. olivier.macherey@mrc-cbu.cam.ac.uk

ABSTRACT
A series of experiments investigated the effects of asymmetric current waveforms on the perception of place and temporal pitch cues. The asymmetric waveforms were trains of pseudomonophasic (PS) pulses consisting of a short, high-amplitude phase followed by a longer (and lower amplitude) opposite-polarity phase. When such pulses were presented in a narrow bipolar ("BP+1") mode and with the first phase anodic relative to the most apical electrode (so-called PSA pulses), pitch was lower than when the first phase was anodic re the more basal electrode. For a pulse rate of 12 pulses per second (pps), pitch was also lower than with standard symmetric biphasic pulses in either monopolar or bipolar mode. This suggests that PSA pulses can extend the range of place-pitch percepts available to cochlear implant listeners by focusing the spread of excitation in a more apical region than common stimulation techniques. Temporal pitch was studied by requiring subjects to pitch-rank single-channel pulse trains with rates ranging from 105 to 1,156 pps; this task was repeated at several intra-cochlear stimulation sites and using both symmetric and pseudomonophasic pulses. For PSA pulses presented to apical electrodes, the upper limit of temporal pitch was significantly higher than that for all the other conditions, averaging 713 pps. Measures of discriminability obtained using the method of constant stimuli indicated that this pitch percept was probably weak. However, a multidimensional scaling study showed that the percept associated with a rate change, even at high rates, was orthogonal to that of a place change and therefore reflected a genuine change in the temporal pattern of neural activity.

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Results of the place-pitch part of experiment 1 (bipolar mode). The bars show the percentage of times PSA-Apex was judged lower than SYM-Apex when presented at the same rate. The error bars show the 95% confidence intervals.
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Fig2: Results of the place-pitch part of experiment 1 (bipolar mode). The bars show the percentage of times PSA-Apex was judged lower than SYM-Apex when presented at the same rate. The error bars show the 95% confidence intervals.

Mentions: Figure 2 shows the percentage of trials where PSA-Apex was judged lower in pitch than SYM-Apex for the three different rates. The bars showing the percentage scores are shown relative to chance level (50%). When the bar is in the upper part of the graph (as is mostly the case), it means PSA-Apex was lower than SYM-Apex whereas a bar in the lower part means it was higher. Mean and 95% confidence intervals are illustrated on the right of the panel and indicate that overall PSA-Apex elicited a significantly lower pitch than SYM-Apex at the three rates tested. A one-way repeated-measure analysis of variance (ANOVA) using the Huynh–Feldt correction also showed a significant effect of rate (F(1.6, 9.7) = 9.69, p = 0.021). The pitch difference between PSA-Apex and SYM-Apex was larger at 258 pps than at 105 pps (p = 0.004) and 644 pps (p = 0.031).FIG. 2


Extending the limits of place and temporal pitch perception in cochlear implant users.

Macherey O, Deeks JM, Carlyon RP - J. Assoc. Res. Otolaryngol. (2010)

Results of the place-pitch part of experiment 1 (bipolar mode). The bars show the percentage of times PSA-Apex was judged lower than SYM-Apex when presented at the same rate. The error bars show the 95% confidence intervals.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046333&req=5

Fig2: Results of the place-pitch part of experiment 1 (bipolar mode). The bars show the percentage of times PSA-Apex was judged lower than SYM-Apex when presented at the same rate. The error bars show the 95% confidence intervals.
Mentions: Figure 2 shows the percentage of trials where PSA-Apex was judged lower in pitch than SYM-Apex for the three different rates. The bars showing the percentage scores are shown relative to chance level (50%). When the bar is in the upper part of the graph (as is mostly the case), it means PSA-Apex was lower than SYM-Apex whereas a bar in the lower part means it was higher. Mean and 95% confidence intervals are illustrated on the right of the panel and indicate that overall PSA-Apex elicited a significantly lower pitch than SYM-Apex at the three rates tested. A one-way repeated-measure analysis of variance (ANOVA) using the Huynh–Feldt correction also showed a significant effect of rate (F(1.6, 9.7) = 9.69, p = 0.021). The pitch difference between PSA-Apex and SYM-Apex was larger at 258 pps than at 105 pps (p = 0.004) and 644 pps (p = 0.031).FIG. 2

Bottom Line: A series of experiments investigated the effects of asymmetric current waveforms on the perception of place and temporal pitch cues.For PSA pulses presented to apical electrodes, the upper limit of temporal pitch was significantly higher than that for all the other conditions, averaging 713 pps.However, a multidimensional scaling study showed that the percept associated with a rate change, even at high rates, was orthogonal to that of a place change and therefore reflected a genuine change in the temporal pattern of neural activity.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council, Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge, UK. olivier.macherey@mrc-cbu.cam.ac.uk

ABSTRACT
A series of experiments investigated the effects of asymmetric current waveforms on the perception of place and temporal pitch cues. The asymmetric waveforms were trains of pseudomonophasic (PS) pulses consisting of a short, high-amplitude phase followed by a longer (and lower amplitude) opposite-polarity phase. When such pulses were presented in a narrow bipolar ("BP+1") mode and with the first phase anodic relative to the most apical electrode (so-called PSA pulses), pitch was lower than when the first phase was anodic re the more basal electrode. For a pulse rate of 12 pulses per second (pps), pitch was also lower than with standard symmetric biphasic pulses in either monopolar or bipolar mode. This suggests that PSA pulses can extend the range of place-pitch percepts available to cochlear implant listeners by focusing the spread of excitation in a more apical region than common stimulation techniques. Temporal pitch was studied by requiring subjects to pitch-rank single-channel pulse trains with rates ranging from 105 to 1,156 pps; this task was repeated at several intra-cochlear stimulation sites and using both symmetric and pseudomonophasic pulses. For PSA pulses presented to apical electrodes, the upper limit of temporal pitch was significantly higher than that for all the other conditions, averaging 713 pps. Measures of discriminability obtained using the method of constant stimuli indicated that this pitch percept was probably weak. However, a multidimensional scaling study showed that the percept associated with a rate change, even at high rates, was orthogonal to that of a place change and therefore reflected a genuine change in the temporal pattern of neural activity.

Show MeSH