ABSTRACT
Tasks assessing perception of a phonemic contrast based on voice onset time (VOT) and a nonspeech analog of a VOT contrast using tone onset time (TOT) were administered to children (ages 7.5 to 15.9 years) identified as having reading disability (RD; n = 21), attention deficit/hyperactivity disorder (ADHD; n = 22), comorbid RD and ADHD (n = 26), or no impairment (NI; n = 26). Children with RD, whether they had been identified as having ADHD or not, exhibited reduced perceptual skills on both tasks as indicated by shallower slopes on category labeling functions and reduced accuracy even at the endpoints of the series where cues are most salient. Correlations between performance on the VOT task and measures of single word decoding and phonemic awareness were significant only in the groups without ADHD. These findings suggest that (a) children with RD have difficulty in processing speech and nonspeech stimuli containing similar auditory temporal cues, (b) phoneme perception is related to phonemic awareness and decoding skills, and (c) the potential presence of ADHD needs to be taken into account in studies of perception in children with RD.
Subject(s)
Attention Deficit Disorder with Hyperactivity/psychology , Dyslexia/psychology , Phonetics , Speech Perception , Attention Deficit Disorder with Hyperactivity/complications , Auditory Perceptual Disorders/psychology , Child , Cues , Discrimination, Psychological , Dyslexia/complications , Female , Humans , MaleABSTRACT
Event-related magnetic fields (ERFs) were recorded from the left hemisphere in nine normal volunteers in response to four consonant-vowel (CV) syllables varying in voice-onset time (VOT). CVs with VOT values of 0 and +20 ms were perceived as /ga/ and those with VOT values of +40 and +60 ms as /ka/. Results showed: (1) a displacement of the N1m peak equivalent current dipole toward more medial locations; and (2) an abrupt reduction in peak magnetic flux strength, as VOT values increased from +20 to +40 ms. No systematic differences were noted between the 0 and +20 ms stimuli or between the +40 and +60 ms CVs. The findings are in agreement with the results of multiunit invasive recordings in non-human primates regarding the spatial and temporal pattern of neuronal population responses in the human auditory cortex which could serve as neural cues for the perception of voicing contrasts.
Subject(s)
Auditory Perception/physiology , Magnetoencephalography , Reaction Time/physiology , Voice , Adult , Auditory Cortex/physiology , Evoked Potentials, Auditory/physiology , Female , Functional Laterality/physiology , Humans , Magnetic Resonance Imaging , Male , SpeechABSTRACT
Previous research has suggested that the direction of short-duration fundamental frequency (F0) perturbations following consonants helps to signal consonant [+voice]/[-voice] (abbreviated as [voice]) status. It has been proposed that the [voice] cue corresponds to the direction and extent of F0 perturbations relative to the overall intonation contour. A competing view, the low-frequency hypothesis, suggests that F0 participates in a more general way whereby low-frequency energy near the consonant contributes to [+voice] judgments. Listeners identified multiple stimulus series, each varying in voice onset time and ranging from /aga/ to /aka/. The series differed in overall intonation contour as well as in the direction of F0 perturbation relative to that contour. Consistent with one version of the low-frequency hypothesis, the F0 value at voicing onset, rather than the relative direction of the F0 perturbation, was the best predictor of [voice] judgments.
