Vowel identification by cochlear implant users: Contributions of duration cues and dynamic spectral cues.

A recent study from our laboratory assessed vowel identification in cochlear implant (CI) users, using full /dVd/ syllables and partial (center- and edges-only) syllables with duration cues neutralized [Donaldson, Rogers, Cardenas, Russell, and Hanna (2013). J. Acoust. Soc. Am. 134, 3021-3028]. CI users' poorer performance for partial syllables as compared to full syllables, and for edges-only syllables as compared to center-only syllables, led to the hypotheses (1) that CI users may rely strongly on vowel duration cues; and (2) that CI users have more limited access to dynamic spectral cues than steady-state spectral cues. The present study tested those hypotheses. Ten CI users and ten young normal hearing (YNH) listeners heard full /dVd/ syllables and modified (center- and edges-only) syllables in which vowel duration cues were either preserved or eliminated. The presence of duration cues significantly improved vowel identification scores in four CI users, suggesting a strong reliance on duration cues. Duration effects were absent for the other CI users and the YNH listeners. On average, CI users and YNH listeners demonstrated similar performance for center-only stimuli and edges-only stimuli having the same total duration of vowel information. However, three CI users demonstrated significantly poorer performance for the edges-only stimuli, indicating apparent deficits of dynamic spectral processing.