Perceptual "vowel spaces" of cochlear implant users: implications for the study of auditory adaptation to spectral shift.
(25/1097)
Cochlear implant (CI) users differ in their ability to perceive and recognize speech sounds. Two possible reasons for such individual differences may lie in their ability to discriminate formant frequencies or to adapt to the spectrally shifted information presented by cochlear implants, a basalward shift related to the implant's depth of insertion in the cochlea. In the present study, we examined these two alternatives using a method-of-adjustment (MOA) procedure with 330 synthetic vowel stimuli varying in F1 and F2 that were arranged in a two-dimensional grid. Subjects were asked to label the synthetic stimuli that matched ten monophthongal vowels in visually presented words. Subjects then provided goodness ratings for the stimuli they had chosen. The subjects' responses to all ten vowels were used to construct individual perceptual "vowel spaces." If CI users fail to adapt completely to the basalward spectral shift, then the formant frequencies of their vowel categories should be shifted lower in both F1 and F2. However, with one exception, no systematic shifts were observed in the vowel spaces of CI users. Instead, the vowel spaces differed from one another in the relative size of their vowel categories. The results suggest that differences in formant frequency discrimination may account for the individual differences in vowel perception observed in cochlear implant users. (+info)
Consequences of neural asynchrony: a case of auditory neuropathy.
(26/1097)
The neural representation of sensory events depends upon neural synchrony. Auditory neuropathy, a disorder of stimulus-timing-related neural synchrony, provides a model for studying the role of synchrony in auditory perception. This article presents electrophysiological and behavioral data from a rare case of auditory neuropathy in a woman with normal hearing thresholds, making it possible to separate audibility from neuropathy. The experimental results, which encompass a wide range of auditory perceptual abilities and neurophysiologic responses to sound, provide new information linking neural synchrony with auditory perception. Findings illustrate that optimal eighth nerve and auditory brainstem synchrony do not appear to be essential for understanding speech in quiet listening situations. However, synchrony is critical for understanding speech in the presence of noise. (+info)
The small world of human language.
(27/1097)
Words in human language interact in sentences in non-random ways, and allow humans to construct an astronomic variety of sentences from a limited number of discrete units. This construction process is extremely fast and robust. The co-occurrence of words in sentences reflects language organization in a subtle manner that can be described in terms of a graph of word interactions. Here, we show that such graphs display two important features recently found in a disparate number of complex systems. (i) The so called small-world effect. In particular, the average distance between two words, d (i.e. the average minimum number of links to be crossed from an arbitrary word to another), is shown to be d approximately equal to 2-3, even though the human brain can store many thousands. (ii) A scale-free distribution of degrees. The known pronounced effects of disconnecting the most connected vertices in such networks can be identified in some language disorders. These observations indicate some unexpected features of language organization that might reflect the evolutionary and social history of lexicons and the origins of their flexibility and combinatorial nature. (+info)
Down syndrome phonology: developmental patterns and intervention strategies.
(28/1097)
This paper describes phonological development in children with Down syndrome paying particular attention to underlying deficits and intervention strategies. The first section provides an overview of factors believed to influence phonological development in this population. The second section describes four aspects of Down syndrome phonology: (1) the prelinguistic stage; (2) the transition to speech; (3) the phonology of the single words; and (4) phonological characteristics of conversational speech with a focus on intelligibility. Intervention strategies associated with each aspect are also presented. Children with Down syndrome are slow to acquire the phonological system of their mother tongue. In spite of normal or nearly normal prelinguistic development, these children are delayed in the use of meaningful speech and slow to acquire a productive vocabulary. In some cases their speech remains unintelligible throughout childhood and adolescence, making it difficult to communicate with those around them. The purpose of this paper is to summarize research on phonological development of children with Down syndrome with attention to underlying deficits and to the speech characteristics of prelinguistic vocalisations as well as words and conversation. Current views on intervention are also described. (+info)
Swallowing and voice effects of Lee Silverman Voice Treatment (LSVT): a pilot study.
(29/1097)
OBJECTIVE: To define the effects of Lee Silverman Voice Treatment (LSVT on swallowing and voice in eight patients with idiopathic Parkinson's disease. METHODS: Each patient received a modified barium swallow (MBS) in addition to voice recording before and after 1 month of LSVT. Swallowing motility disorders were defined and temporal measures of the swallow were completed from the MBS. Voice evaluation included measures of vocal intensity, fundamental frequency, and the patient's perception of speech change. RESULTS: before LSVT, the most prevalent swallowing motility disorders were oral phase problems including reduced tongue control and strength. Reduced tongue base retraction resulting in residue in the vallecula was the most common disorder in the pharyngeal stage of the swallow. Oral transit time (OTT) and pharyngeal transit time (PTT) were prolonged. After LSVT, there was an overall 51% reduction in the number of swallowing motility disorders. Some temporal measures of swallowing were also significantly reduced as was the approximate amount of oral residue after 3 ml and 5 ml liquid swallows. Voice changes after LSVT included a significant increase in vocal intensity during sustained vowel phonation as well as during reading. CONCLUSIONS: LSVT seemingly improved neuromuscular control of the entire upper aerodigestive tract, improving oral tongue and tongue base function during the oral and pharyngeal phases of swallowing as well as improving vocal intensity. (+info)
Brain mechanisms for reading words and pseudowords: an integrated approach.
(30/1097)
The present study tested two predictions of dual-process models of reading: (i) that the brain structures involved in sublexical phonological analysis and those involved in whole-word phonological access during reading are different; and (ii) that reading of meaningful items, by means of the addressed phonology process, is mediated by different brain structures than reading of meaningless letter strings. We obtained brain activation profiles using Magnetic Source Imaging and, in addition, pronunciation latencies during reading of: (i) exception words (primarily involving addressed phonology and having meaning), (ii) pseudohomophones (requiring assembled phonology and having meaning), and (iii) pseudowords (requiring assembled phonology but having no meaning). Reading of meaningful items entailed a high degree of activation of the left posterior middle temporal gyrus (MTGp) and mesial temporal lobe areas, whereas reading the meaningless pseudowords was associated with much reduced activation of these two regions. Reading of all three types of print resulted in activation of the posterior superior temporal gyrus (STGp), inferior parietal and basal temporal areas. In addition, pronunciation speed of exception words correlated significantly with the onset of activity in MTGp but not STGp, whereas the opposite was true for pseudohomophones and pseudowords. These findings are consistent with the existence of two different brain mechanisms that support phonological processing in word reading: one mechanism that subserves assembled phonology and depends on the posterior part of STGp, and a second mechanism that is responsible for pronouncing words with rare print-to-sound correspondences and does not necessarily involve this region but instead appears to depend on MTGp. (+info)
Phonological awareness in children with Down syndrome.
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Research in the area of phonological awareness has mainly focused on the nature of the relationship between reading ability and awareness of phonemes. However, a recent study of phonological awareness in children with Down syndrome questioned the existence of any necessary relationship (Cossu, Rossini & Marshall, 1993). This paper describes a study of phonological awareness in children with Down syndrome with varying levels of reading ability. The sample consisted of 10 male and 7 female children with Down syndrome (aged 9 years 2 months to 14 years 5 months). All children received a battery of tests which consisted of assessments of: 1) phonological awareness, 2) reading and spelling competence, 3) non-word reading and spelling ability, and 4) non-verbal measures. Children with Down syndrome demonstrated measurable levels of phonological awareness. Significant positive correlations were found between phonological awareness and: reading and spelling competence, ability to spell non-words and non-verbal measures. (+info)
Influence of onset density on spoken-word recognition.
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Previous research has suggested that the initial portion of a word activates similar sounding words that compete for recognition. Other research has shown that the number of similar sounding words that are activated influences the speed and accuracy of recognition. Words with few neighbors are processed more quickly and accurately than words with many neighbors. The influences of the number of lexical competitors in the initial part of the word were examined in a shadowing and a lexical-decision task. Target words with few neighbors that share the initial phoneme were responded to more quickly than target words with many neighbors that share the initial phoneme. The implications of onset-density effects for models of spoken-word recognition are discussed. (+info)