Multichannel Place Pitch Sensitivity in Cochlear Implant Recipients

Abstract

Cochlear implant recipients perceive a rise in pitch when the site of stimulation is moved from the apex toward the base. The place pitch sensitivity is typically measured using the stimulation of single channels. However, all current cochlear implant devices stimulate multiple channels simultaneously or with pulses temporally interleaved. The primary goal of the present study is to test whether the sensitivity of a cochlear implant recipient to changes in perceived pitch associated with changes of place of excitation improves or deteriorates when the number of active channels is increased, compared with stimulation with only one active channel. Place pitch sensitivity was recorded in four Nucleus CI24 subjects as a function of number of active channels (from 1 to 8). Just noticeable differences were estimated from a constant stimuli 2AFC pitch-ranking experiment with roving loudness. Reference and comparison stimuli contained the same number of active channels but were shifted one or two electrodes toward the base or toward the apex. The place pitch sensitivity was measured using monopolar stimulation at two locations along the electrode array. To minimize cues related to loudness, the multichannel stimuli were loudness balanced relative to the single-channel stimuli presented at C-level. The number of active channels did not affect place pitch sensitivity. This is consistent with a model that compares the edges of the excitation pattern irrespective of the overlap between excitation patterns. There was a significant difference in sensitivity to place pitch among subjects.The average just noticeable differences of place pitch, extrapolated from a fitting procedure, for the subjects ranged from 0.25 mm to 0.46 mm.

Discrimination between sequential and simultaneous virtual channels with electrical hearing

“…The hypothesis that patients are attending to the skirts rather than the peak of the excitation patterns is consistent with Laneau and Wouters (2004), who found that with multichannel stimulation, pitch ranking can be reliably performed by attending to differences in the edges of stimulation. To the extent that the IPI might influence the spread of excitation in a sequential VC, it might be worthwhile to compare pitch-ranking across small a steps for simultaneous and sequential VCs.…”

Gender Categorization Is Abnormal in Cochlear Implant Users

“…1, right-most column). Using stimulation patterns comprising one to eight adjacent electrodes (the latter is relatively similar to the stimulation pattern of the vowels in our experiment), Laneau and Wouters (2004) found that CI listeners have just-noticeable differences for place shifts of about 0.5 electrodes. Yet, the CI users in our experiment did not use the VTL cue for gender categorization.…”

Effects of stimulation configurations on place pitch discrimination in cochlear implants

“…It is worth noting that Laneau and Wouters (2004) reported relatively better performance in electrode discrimination with four Nucleus-24 subjects. When converting to the d 0 s for adjacent channels, as their results were represented in terms of just noticeable differences, they are roughly in the range of 1.5 and 3.3, corresponding to cumulative d 0 s for the entire array of approximately 31.5 and 69.3, respectively, after multiplying each by 21.…”

“…Recent studies have reported pitch discrimination of virtual channels (Donaldson et al, 2005;Kwon and van den Honert, 2006;Firszt et al, 2007) and discrimination of stimuli on multiple channels (Laneau and Wouters, 2004). These studies essentially capitalized upon the CI users' abilities to discriminate between adjacent channels, presuming sufficiently good ability to carry out such demanding tasks.…”