Limits...
Rate discrimination, gap detection and ranking of temporal pitch in cochlear implant users.

Cosentino S, Carlyon RP, Deeks JM, Parkinson W, Bierer JA - J. Assoc. Res. Otolaryngol. (2016)

Bottom Line: There was a marginal across-electrode correlation between gap detection and rate discrimination at 400 pps, but neither measure correlated with rate discrimination at 100 pps.Similarly, there was a highly significant across-subject correlation between gap detection and rate discrimination at 400, but not 100 pps, and these two correlations differed significantly from each other.The results are consistent with the upper limit of rate discrimination sharing a common basis with gap detection.

View Article: PubMed Central - PubMed

Affiliation: MRC Cognition and Brain Sciences Unit, 15 Chaucer Rd, Cambridge, CB2 7EF, UK. stefano.cosentino@mrc-cbu.cam.ac.uk.

ABSTRACT
Cochlear implant (CI) users have poor temporal pitch perception, as revealed by two key outcomes of rate discrimination tests: (i) rate discrimination thresholds (RDTs) are typically larger than the corresponding frequency difference limen for pure tones in normal hearing listeners, and (ii) above a few hundred pulses per second (i.e. the "upper limit" of pitch), CI users cannot discriminate further increases in pulse rate. Both RDTs at low rates and the upper limit of pitch vary across listeners and across electrodes in a given listener. Here, we compare across-electrode and across-subject variation in these two measures with the variation in performance on another temporal processing task, gap detection, in order to explore the limitations of temporal processing in CI users. RDTs were obtained for 4-5 electrodes in each of 10 Advanced Bionics CI users using two interleaved adaptive tracks, corresponding to standard rates of 100 and 400 pps. Gap detection was measured using the adaptive procedure and stimuli described by Bierer et al. (JARO 16:273-284, 2015), and for the same electrodes and listeners as for the rate discrimination measures. Pitch ranking was also performed using a mid-point comparison technique. There was a marginal across-electrode correlation between gap detection and rate discrimination at 400 pps, but neither measure correlated with rate discrimination at 100 pps. Similarly, there was a highly significant across-subject correlation between gap detection and rate discrimination at 400, but not 100 pps, and these two correlations differed significantly from each other. Estimates of low-rate sensitivity and of the upper limit of pitch, obtained from the pitch ranking experiment, correlated well with rate discrimination for the 100- and 400-pps standards, respectively. The results are consistent with the upper limit of rate discrimination sharing a common basis with gap detection. There was no evidence that this limitation also applied to rate discrimination at lower rates.

No MeSH data available.


Scatter plot between RDR400 and GDT as measured across subjects.
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Fig5: Scatter plot between RDR400 and GDT as measured across subjects.

Mentions: Across subjects (i.e. averaging over electrodes), the RDR100 scores did not correlate with RDR400 (r = 0.49; df = 8, p = 0.15) or with GDT (r = 0.43; df = 8, p = 0.2). There was, however, a strong and highly significant across-subject correlation between GDT and RDR400 (r = 0.90; df = 8, p < 0.01), as shown in Figure 5. Differences in performance across subjects can be broadly attributed to two sources of variance: cognitive and sensory. Cognitive differences are due to, for instance, subject’s concentration, intelligence and to other high level abilities that may affect performance on behavioural tasks. Sensory differences, which may arise from neural survival or from the position of the electrodes inside the cochlea, can also contribute to differences in test performance for different subjects. In our data, the correlation with GDT is significantly greater for RDR400 than for RDR100 (Williams’ test, p < 0.05). Under the assumption that cognitive differences across subjects affect both tasks in equal amounts, this outcome suggests that the across-subject correlation between RDR400 and GDT is, at least in part, due to a common sensory limitation, and that the commonality of this limitation is greater than that between RDR100 and GDT. It is worth recalling that the two rate discrimination measures were obtained concurrently using two interleaved adaptive procedures, and this may have helped equate cognitive factors between the two tasks. Taken together, the results of both the across-subject and the across-electrode correlations point to a link between gap detection and the upper limit of rate discrimination, but not between the GDT and rate discrimination at 100 pps.FIG. 5


Rate discrimination, gap detection and ranking of temporal pitch in cochlear implant users.

Cosentino S, Carlyon RP, Deeks JM, Parkinson W, Bierer JA - J. Assoc. Res. Otolaryngol. (2016)

Scatter plot between RDR400 and GDT as measured across subjects.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4940289&req=5

Fig5: Scatter plot between RDR400 and GDT as measured across subjects.
Mentions: Across subjects (i.e. averaging over electrodes), the RDR100 scores did not correlate with RDR400 (r = 0.49; df = 8, p = 0.15) or with GDT (r = 0.43; df = 8, p = 0.2). There was, however, a strong and highly significant across-subject correlation between GDT and RDR400 (r = 0.90; df = 8, p < 0.01), as shown in Figure 5. Differences in performance across subjects can be broadly attributed to two sources of variance: cognitive and sensory. Cognitive differences are due to, for instance, subject’s concentration, intelligence and to other high level abilities that may affect performance on behavioural tasks. Sensory differences, which may arise from neural survival or from the position of the electrodes inside the cochlea, can also contribute to differences in test performance for different subjects. In our data, the correlation with GDT is significantly greater for RDR400 than for RDR100 (Williams’ test, p < 0.05). Under the assumption that cognitive differences across subjects affect both tasks in equal amounts, this outcome suggests that the across-subject correlation between RDR400 and GDT is, at least in part, due to a common sensory limitation, and that the commonality of this limitation is greater than that between RDR100 and GDT. It is worth recalling that the two rate discrimination measures were obtained concurrently using two interleaved adaptive procedures, and this may have helped equate cognitive factors between the two tasks. Taken together, the results of both the across-subject and the across-electrode correlations point to a link between gap detection and the upper limit of rate discrimination, but not between the GDT and rate discrimination at 100 pps.FIG. 5

Bottom Line: There was a marginal across-electrode correlation between gap detection and rate discrimination at 400 pps, but neither measure correlated with rate discrimination at 100 pps.Similarly, there was a highly significant across-subject correlation between gap detection and rate discrimination at 400, but not 100 pps, and these two correlations differed significantly from each other.The results are consistent with the upper limit of rate discrimination sharing a common basis with gap detection.

View Article: PubMed Central - PubMed

Affiliation: MRC Cognition and Brain Sciences Unit, 15 Chaucer Rd, Cambridge, CB2 7EF, UK. stefano.cosentino@mrc-cbu.cam.ac.uk.

ABSTRACT
Cochlear implant (CI) users have poor temporal pitch perception, as revealed by two key outcomes of rate discrimination tests: (i) rate discrimination thresholds (RDTs) are typically larger than the corresponding frequency difference limen for pure tones in normal hearing listeners, and (ii) above a few hundred pulses per second (i.e. the "upper limit" of pitch), CI users cannot discriminate further increases in pulse rate. Both RDTs at low rates and the upper limit of pitch vary across listeners and across electrodes in a given listener. Here, we compare across-electrode and across-subject variation in these two measures with the variation in performance on another temporal processing task, gap detection, in order to explore the limitations of temporal processing in CI users. RDTs were obtained for 4-5 electrodes in each of 10 Advanced Bionics CI users using two interleaved adaptive tracks, corresponding to standard rates of 100 and 400 pps. Gap detection was measured using the adaptive procedure and stimuli described by Bierer et al. (JARO 16:273-284, 2015), and for the same electrodes and listeners as for the rate discrimination measures. Pitch ranking was also performed using a mid-point comparison technique. There was a marginal across-electrode correlation between gap detection and rate discrimination at 400 pps, but neither measure correlated with rate discrimination at 100 pps. Similarly, there was a highly significant across-subject correlation between gap detection and rate discrimination at 400, but not 100 pps, and these two correlations differed significantly from each other. Estimates of low-rate sensitivity and of the upper limit of pitch, obtained from the pitch ranking experiment, correlated well with rate discrimination for the 100- and 400-pps standards, respectively. The results are consistent with the upper limit of rate discrimination sharing a common basis with gap detection. There was no evidence that this limitation also applied to rate discrimination at lower rates.

No MeSH data available.