ABSTRACT
BACKGROUND AND OBJECTIVES: Although many cochlear implant (CI) recipients receive significant benefits from using the implants, speech perception ability is still known to vary among CI users, and the variability is closely related to the ability of users to process temporal information. As one of the important temporal cues for speech perception in CI users, voice onset time (VOT) can be used to examine behavioral perception and neural correlates of temporal processing. In this study, we measured categorical perception and N1-P2 cortical auditory evoked potentials (CAEPs) using a /ba/-/pa/ VOT continuum in CI users as well as in normal-hearing (NH) listeners. SUBJECTS AND METHOD: Ten CI subjects and 11 NH controls participated in syllable identification tasks and in electroencephalography recording. CI subjects were divided into two groups, which were ‘good’ and ‘poor’ performers based on their speech perception scores. The stimuli used in both experiments were a synthetic /ba/-/pa/ VOT continuum. The identification boundary and N1-P2 peak-to-peak amplitude were measured for each subject group. RESULTS: Behavioral results revealed that poor CI performers had a delayed identification boundary compared to NH listeners and good CI performers. However, N1-P2 peak-to-peak amplitudes in both good and poor CI performers were significantly smaller than those in NH group. CONCLUSION: N1-P2 amplitudes reflected decreased auditory cortical activity of temporal cues in CI users. The categorical perception of good CI performers was similar to that of NH listeners, whereas their cortical responses were decreased to the level similar to that of poor CI performers. This finding indicates that CAEPs would be more sensitive to altered temporal processing of CI users than to behavioral measures.
Subject(s)
Cochlear Implants , Cues , Electroencephalography , Evoked Potentials, Auditory , Methods , Speech Perception , VoiceABSTRACT
Objective To investigate the perception of Mandarin's tones by children with speech development disorders so as to provide a theoretical basis for clinical rehabilitation.Methods Thirty children with speech development disorders (DPDs) aged 4 to 6 were matched with 30 healthy counterparts as a control group.Both groups underwent the tone perception experiment,which included tone identification and discrimination tasks.The speech stimuli were 11 computer-simulated voices expressing a continuum of sounds from Mandarin speech ranging from /bá/ to /bà/.The two groups were compared in their ability to identify and differentiate the tones.Results Both groups showed typicalS-shaped identification curves in a category pattern.The category boundaries of the control group were between stimulus steps 6 and 7,significantly different from those of the experimental group where the boundary fell between stimulus steps 5 and 6.On the distinguishing curve,both groups presented obvious peak values.The stimulus steps of the peaks and the crossing points of the identification curves were consistent.In addition,the average ahsolnte value (b1) of the identification curve and the peaks' degree of steepness (DP) of the DPD group's distinguishing curve were significantly lower than those of the control group.At the same time,the average boundary width (Wcb) was significantly higher than that of the control group.Conclusion Children with speech development disorders perceive Mandarin tones with categories different from those of normal children.They may have difficulty in perceiving tones,which might be an important factor leading to pronunciation errors.