Within-Subjects Comparison of the HiRes and Fidelity120 Speech Processing Strategies: Speech Perception and Its Relation to Place-Pitch Sensitivity

OBJECTIVES:Previous studies have confirmed that current steering can increase the number of discriminable pitches available to many cochlear implant (CI) users; however, the ability to perceive additional pitches has not been linked to improved speech perception. The primary goals of this study were to determine (1) whether adult CI users can achieve higher levels of spectral cue transmission with a speech processing strategy that implements current steering (Fidelity120) than with a predecessor strategy (HiRes) and, if so, (2) whether the magnitude of improvement can be predicted from individual differences in place-pitch sensitivity. A secondary goal was to determine whether Fidelity120 supports higher levels of speech recognition in noise than HiRes. DESIGN:A within-subjects repeated measures design evaluated speech perception performance with Fidelity120 relative to HiRes in 10 adult CI users. Subjects used the novel strategy (either HiRes or Fidelity120) for 8 wks during the main study; a subset of five subjects used Fidelity120 for three additional months after the main study. Speech perception was assessed for the spectral cues related to vowel F1 frequency, vowel F2 frequency, and consonant place of articulation; overall transmitted information for vowels and consonants; and sentence recognition in noise. Place-pitch sensitivity was measured for electrode pairs in the apical, middle, and basal regions of the implanted array using a psychophysical pitch-ranking task. RESULTS:With one exception, there was no effect of strategy (HiRes versus Fidelity120) on the speech measures tested, either during the main study (N = 10) or after extended use of Fidelity120 (N = 5). The exception was a small but significant advantage for HiRes over Fidelity120 for consonant perception during the main study. Examination of individual subjectsʼ data revealed that 3 of 10 subjects demonstrated improved perception of one or more spectral cues with Fidelity120 relative to HiRes after 8 wks or longer experience with Fidelity120. Another three subjects exhibited initial decrements in spectral cue perception with Fidelity120 at the 8-wk time point; however, evidence from one subject suggested that such decrements may resolve with additional experience. Place-pitch thresholds were inversely related to improvements in vowel F2 frequency perception with Fidelity120 relative to HiRes. However, no relationship was observed between place-pitch thresholds and the other spectral mea