Modeling and perception of 'gesture reduction'. (17/1097)

The phenomenon of vowel reduction is investigated by modeling 'gesture reduction' with the use of the Distinctive Region Model (DRM). First, a definition is proposed for the term gesture, i.e. an acoustically efficient command aimed at deforming, in the time domain, the area function of the vocal tract. Second, tests are reported on the perception of vowel-to-vowel transitions obtained with reduced gestures. These tests show that a dual representation of formant transitions is required to explain the reduction phenomenon: the trajectory in the F(1)-F(2) plane and the time course of the formant changes. The results also suggest that time-domain integration of the trajectories constitutes an integral part of the auditory processing of transitions. Perceptual results are also discussed in terms of the acoustic traces of DRM gestures.  (+info)

Identity matching of consonant-vowel-consonant words by prereaders. (18/1097)

Using an identity matching-to-sample procedure, normally developing prereaders who matched individual letters with high accuracy (e.g., m and s) did not show high accuracy in matching three-letter printed words that differed only in the first letter (e.g., mad and sad). Teachers and researchers should not assume that children who can discriminate individual letters can also discriminate minimally different words that contain those letters.  (+info)

Lexical, syntactic, and stress-pattern cues for speech segmentation. (19/1097)

Many sources of segmentation information are available in speech. Previous research has shown that one or another segmentation cue is used by listeners under certain circumstances. However, it has also been shown that none of the cues are absolutely reliable. Therefore, it is likely that people use a combination of segmentation cues when listening to normal speech. This study addresses the issue of how young adults use multiple segmentation cues (lexical, syntactic, and stress-pattern) in combination to break up continuous speech. Evidence that people use more than one cue at a time was found. Furthermore, the results suggest that people can use segmentation cues flexibly such that remaining cues are relied upon more heavily when other information is missing.  (+info)

Phonological and semantic fluencies are mediated by different regions of the prefrontal cortex. (20/1097)

Verbal phonological and semantic fluencies were investigated in 24 patients with unilateral prefrontal lesions and 10 normal control subjects. Lesions were limited to small areas within either the dorsolateral (Brodmann's area 46/9) or ventromedial (posterior part of the gyrus rectus) cortices. In a phonological fluency task, patients with lesions to the left dorsolateral region were impaired. In semantic fluency, not only the left dorsolateral group but also the two right frontal damaged groups performed worse than the control group. In agreement with previous studies, our results show that the phonological fluency is mediated by the left dorsolateral prefrontal cortex. In contrast to this, performance on the semantic fluency task depends on a wider portion of the prefrontal cortex involving the left and right dorsolateral and the right ventromedial areas.  (+info)

Anatomical risk factors for phonological dyslexia. (21/1097)

Successful behavioral genetic studies require precise definition of a homogenous phenotype. This study searched for anatomical markers that might restrict variability in the reading disability phenotype. The subjects were 15 college students (8 male/7 female) diagnosed with a reading disability (RD) and 15 controls (8 males/7 females). All subjects completed a cognitive and reading battery. Only 11 of the RD subjects had a phonological deficit [phonological dyslexia (PD): pseudo word decoding scores < 90 (27th percentile)]. Thirteen RD (9 PD) and 15 controls received a volumetric MRI scan. Four anatomical measures differentiated the PD group from the remainder of the subjects: (i) marked rightward cerebral asymmetry, (ii) marked leftward asymmetry of the anterior lobe of the cerebellum, (ii) combined leftward asymmetry of the planum and posterior ascending ramus of the sylvian fissure, and (iv) a large duplication of Heschl's gyrus on the left. When these four measures were normalized and summed, the resulting variable predicted short- and long-term phonological memory. By contrast, oral and written comprehension skills were predicted by a different anatomical variable: low cerebral volume. These findings provide neurobiological support for an RD phenotype characterized by phonological deficits in the presence of normal or superior comprehension. The study of individual variation in cortical structure may provide a useful link between genotype and behavior.  (+info)

Conjoint and extended neural networks for the computation of speech codes: the neural basis of selective impairment in reading words and pseudowords. (22/1097)

The computation of speech codes (i.e. phonology) is an important aspect of word reading. Understanding the neural systems and mech- anisms underlying phonological processes provides a foundation for the investigation of language in the brain. We used high-resolution three-dimensional positron emission tomography (PET) to investigate neural systems essential for phonological processes. The burden of neural activities on the computation of speech codes was maximized by three rhyming tasks (rhyming words, pseudowords and words printed in mixed letter cases). Brain activation patterns associated with these tasks were compared with those of two baseline tasks involving visual feature detection. Results suggest strong left lateralized epicenters of neural activity in rhyming irrespective of gender. Word rhyming activated the same brain regions engaged in pseudoword rhyming, suggesting conjoint neural networks for phonological processing of words and pseudowords. However, pseudoword rhyming induced the largest change in cerebral blood flow and activated more voxels in the left posterior prefrontal regions and the left inferior occipital-temporal junction. In addition, pseudoword rhyming activated the left supramarginal gyrus, which was not apparent in word rhyming. These results suggest that rhyming pseudowords requires active participation of extended neural systems and networks not observed for rhyming words. The implications of the results on theories and models of visual word reading and on selective reading dysfunctions after brain lesions are discussed.  (+info)

Discrimination of non-native consonant contrasts varying in perceptual assimilation to the listener's native phonological system. (23/1097)

Classic non-native speech perception findings suggested that adults have difficulty discriminating segmental distinctions that are not employed contrastively in their own language. However, recent reports indicate a gradient of performance across non-native contrasts, ranging from near-chance to near-ceiling. Current theoretical models argue that such variations reflect systematic effects of experience with phonetic properties of native speech. The present research addressed predictions from Best's perceptual assimilation model (PAM), which incorporates both contrastive phonological and noncontrastive phonetic influences from the native language in its predictions about discrimination levels for diverse types of non-native contrasts. We evaluated the PAM hypotheses that discrimination of a non-native contrast should be near-ceiling if perceived as phonologically equivalent to a native contrast, lower though still quite good if perceived as a phonetic distinction between good versus poor exemplars of a single native consonant, and much lower if both non-native segments are phonetically equivalent in goodness of fit to a single native consonant. Two experiments assessed native English speakers' perception of Zulu and Tigrinya contrasts expected to fit those criteria. Findings supported the PAM predictions, and provided evidence for some perceptual differentiation of phonological, phonetic, and nonlinguistic information in perception of non-native speech. Theoretical implications for non-native speech perception are discussed, and suggestions are made for further research.  (+info)

The relevance of a nonword repetition task to assess phonological short-term memory in individuals with Down syndrome. (24/1097)

Phonological short-term memory capacity is generally measured with a word span task or a digit span task. Another way to measure it is to use a nonword repetition task. Gathercole and Adams (1993) claimed that this procedure can be used with children as young as two-years old. It seems that in normally developing children the quality of nonword repetition is influenced both by the length of nonwords and by the degree of wordlikeness. Can the phonological short-term memory of individuals with Down syndrome be assessed with a nonword repetition task? In order to answer this question, we decided to replicate Gathercole and collaborators' experiments (1991,1993) but with individuals with Down syndrome. The quality of nonword repetition in individuals with Down syndrome is, as in normally developing children, influenced both by the length of nonwords and by their degree of wordlikeness. Furthermore, our results seem to confirm the hypothesis which states that nonwords are temporarily stored in the phonological short-term memory system. As this system has a limited capacity, both normally developing children and people with Down syndrome recall more short nonwords than long nonwords. In conclusion, nonword repetition is a reliable task with which to assess phonological short-term memory in individuals with Down syndrome as well as in normally developing children.  (+info)