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Purpose: Children with dyslexia have been suggested to experience deficits in both categorical perception (CP) and speech identification in noise (SIN) perception. However, results regarding both abilities are inconsistent, and the relationship between them is still unclear. Therefore, this study aimed to investigate the relationship between CP and the psychometric function of SIN perception. Method: Sixteen children with dyslexia, 16 chronological-age controls, and 16 reading-level controls were evaluated in CP of a voicing continuum and in consonant identification in both stationary and fluctuating noises. Results: There was a small but significant impairment in speech identification performance of children with dyslexia in stationary noise compared with chronological age-matched controls (but not reading level-matched controls). However, their performance increased in a fluctuating background, hence suggesting normal masking and unmasking effects and preserved sensory processing of speech information. Regarding CP, location of the phoneme boundary differed in the children with dyslexia compared with both control groups. However, scrutinizing individual profiles failed to reveal consistently poor performance in SIN and CP tasks. In addition, there was no significant correlation between CP, SIN perception, and reading scores in the group with dyslexia. Conclusions: The relationship between the SIN deficit and CP, and how they potentially affect reading in children with dyslexia, remains unclear. However, these results are inconsistent with the notion that children with dyslexia suffer from a low-level temporal processing deficit and rather suggest a role of nonsensory (e.g., attentional) factors in their speech perception difficulties., About 7% of school children experience severe and persistent difficulty in learning to read and write despite adequate intelligence, sensory and cognitive abilities, and educational opportunities (Snowling, 2000). This specific [...]

Purpose: This study assessed the role of spectro-temporal modulation cues in the discrimination of 2 phonetic contrasts (voicing and place) for young infants. Method: A visual-habituation procedure was used to assess the ability of French-learning 6-month-old infants with normal hearing to discriminate voiced versus unvoiced (/aba/-/apa/) and labial versus dental (/aba/-/ada/) stop consonants. The stimuli were processed by tone-excited vocoders to degrade frequency-modulation cues while preserving: (a) amplitude-modulation (AM) cues within 32 analysis frequency bands, (b) slow AM cues only ( Results: Infants exhibited discrimination responses for both phonetic contrasts in each processing condition. However, when fast AM cues were degraded, infants required a longer exposure to vocoded stimuli to reach the habituation criterion. Conclusions: Altogether, these results indicate that the processing of modulation cues conveying phonetic information on voicing and place is 'functional' at 6 months. The data also suggest that the perceptual weight of fast AM speech cues may change during development., Large numbers of studies have investigated separately auditory and speech perception in infants (for a review, see Kuhl, 2004; Saffran, Werker, & Werner, 2006), but knowledge about the auditory capacities [...]

Purpose: The capacity of 6-month-old infants to discriminate a voicing contrast (/aba/-/apa/) on the basis of amplitude modulation (AM) cues and frequency modulation (FM) cues was evaluated. Method: Several vocoded speech conditions were designed to either degrade FM cues in 4 or 32 bands or degrade AM in 32 bands. Infants were familiarized to the vocoded stimuli for a period of either 1 or 2 min. Vocoded speech discrimination was assessed using the head-turn preference procedure. Results: Infants discriminated /aba/ from /apa/ in each condition; however, familiarization time was found to influence strongly infants' responses (i.e., their preference for novel vs. familiar stimuli). Conclusions: Six-month-old infants do not require FM cues and can use the slowest (< 16 Hz) AM cues to discriminate voicing. Moreover, 6-month-old infants can use AM cues extracted from only 4 broad-frequency bands to discriminate voicing. Key Words: speech perception, vocoder, modulation cues, normal-hearing infants, Most recent studies about speech perception in infants have focused on how they acquire the phonological properties of their native language in a variety of learning contexts (see Kuhl et [...]

Purpose: To investigate the capacity of young children and adults with normal hearing to discriminate speech on the basis of either relatively slow (temporal envelope, E) or fast (temporal fine structure, TFS) auditory cues. Method: Vowel-consonant-vowel nonsense disyllables were processed to preserve either the E or the TFS information in 16 adjacent frequency bands. The band signals were then recombined and resulting stimuli were presented for discrimination to adults or 5-, 6-, and 7-year-old children using an odd-ball paradigm. Discrimination scores (d) and response latencies were measured in each listener. No training was given to listeners. Results: Overall, discrimination scores were high (d&apos; [greater than or equal to] 1) in all speech-processing conditions, and did not differ across age groups. Overall, and irrespective of age, greater discrimination scores and shorter response latencies were observed for E speech than for TFS speech. Conclusions: These results suggest that normal-hearing children are able to encode and use E and TFS speech cues at adult levels by the age of 5 years. TFS- and E-coded speech stimuli might therefore prove to be a useful tool for the investigation of the developmental time course of speech perception, and for the early diagnosis of peripheral and central auditory processing disorders. KEY WORDS: speech temporal cues, consonant discrimination, speech perception, Recent studies have suggested a new dichotomy in auditory perception between so-called "temporal envelope" and "temporal fine structure" cues (e.g., Drullman, 1995; Flanagan, 1980; Smith, Delgutte, & Oxenham, 2002; Xu [...]

This study compares amplitude-modulation (AM) masking in listeners with normal hearing and in listeners with a hearing loss. To address this issue, we measured the detection of sinusoidal AM applied to a white noise carrier, as a function of the frequency of a masking sinusoidal AM applied to the same noise carrier. These input filter patterns were measured for four listeners with normal hearing and three listeners with moderate or mild-to-severe sensorineural hearing losses. Stimuli were presented at 50 dB SL for all listeners with normal hearing and for two of the three listeners with hearing loss. The third listener with hearing loss was tested at 25 dB SL. For the listeners with normal hearing, the input filter patterns obtained for 100-Hz signal modulation had a broad bandpass characteristic. All input filter patterns showed a primary masking peak at 100 Hz. A secondary masking peak was apparent also at 50 Hz. For the listeners with impaired hearing, the unmasked modulation thresholds were similar to those measured in the listeners with normal hearing. One listener with moderate hearing loss exhibited a broadly tuned input filter pattern with a masking peak at 100 Hz, but no secondary peak. The two other listeners with moderate or mild-to-severe sensorineural hearing loss showed no main masking peak and increased thresholds at low masker modulation frequencies. These results suggest that cochlear damage may affect performance in a modulation masking task. KEY WORDS: amplitude modulation, masking, temporal resolution, normal hearing, cochlear damage

This study evaluates the ability to process auditory temporal-envelope cues in a group of 6 children with dyslexia (mean age: 10;10 years;months). To address this issue, we measured (a) temporal modulation transfer functions (TMTFs), that is, the detection thresholds of sinusoidal amplitude modulation (SAM) applied to a white noise carrier, as a function of modulation frequency, [f.sub.m] ([f.sub.m] was 4, 16, 64, 256, and 1024 Hz) and (b) identification performance for vowel-consonant-vowel (VCV) stimuli over 5 sessions. VCV stimuli were either unprocessed or digitally processed to remove the original spectral information, resulting in a time-varying speech envelope amplitude modulating a noise carrier. The same tests were conducted in 6 normal control children (mean age: 11;6 years;months) and 6 normal control adults (mean age: 24;8 years;months). SAM thresholds were similar in normal children and adults. For both normal groups, TMTFs were low pass in shape and showed low between-listener variability. TMTFs measured in children with dyslexia showed higher between-listener variability: TMTFs were band pass in 2 children, flat in 1 child, and low pass in the 3 others. Overall, SAM thresholds were higher in children with dyslexia than in normal children at [f.sub.m] = 4 and 1024 Hz. Unprocessed-speech identification performance was nearly perfect in normal children and adults, and impaired in children with dyslexia. "Speech-envelope noise" identification performance was poorer in normal children and children with dyslexia than in normal adults. Performance improved across sessions in normal children and adults, but remained constant in children with dyslexia. Compared to normal children, children with dyslexia showed poorer reception of voicing, manner, and place of articulation for unprocessed speech and poorer reception of voicing for "speech-envelope noise." Taken together, these results support the hypothesis that some children with dyslexia may show abnormal auditory temporal-envelope processing. Such a deficit, in turn, may explain the difficulties of children with dyslexia with speech perception. KEY WORDS: dyslexia, language impairment, temporal envelope, temporal acuity, auditory perception, Continuous speech shows pronounced low-frequency amplitude modulations in its temporal envelope, with most prominent modulation frequencies near the average syllabic rate of 3-4 Hz (Houtgast & Steeneken, 1985). A number [...]