This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The objective of this project is to identify the neurophysiological processes underlying perception of speech phonemes in children. Phonemes are complex spectrotemporal acoustic patterns that carry the linguistic information in speech. A principal defining characteristic of these sounds is that they are perceived categorically. That is, different acoustic stimuli tend to be grouped into perceptual categories (phonemes), resulting in better discrimination across than within category boundaries. In a recent study using fMRI in healthy adults, we showed significant activation in the left superior temporal sulcus associated with the categorical perception of speech phonemes. However, no similar neuroimaging studies of phonetic perception have yet been performed with children. There have been a few functional neuroimaging studies examining developmental changes in the neural bases of higher linguistic processing. These have typically shown similar overall patterns of activation across children, adolescents, and adults, but age-related increases in left lateralization or functional specialization of brain regions have also been reported. In addition, age-related changes in speech perception have been shown, with perception of native speech phonemes becoming increasingly categorical throughout infancy and young childhoodsuper 5nosupersub . Based on these findings, we hypothesize that children will show patterns of brain activation associated with categorical perception that are highly similar to those previously seen in adults, including the preferential engagement of the left temporal lobe, but that the degree of left-temporal dominance will increase with age and this developmental change will be related to increasing categorical perception of speech sounds. This hypothesis will be tested by examining the relationship between the degree of categorical perception and the extent of left hemisphere dominance as a function of development. In addition, it is expected that this study of phonetic perception in children will also serve as a baseline and provide pilot data for a future NIH application aimed at examining phonetic perception deficits in dyslexic children.
Specific aims : 1. Identify brain areas underlying categorical and continuous perception of speech and speech-like sounds in children using functional magnetic resonance imaging. 2.Compare the behavioral and neuroimaging results obtained with children aged 7 to 9 years with those of children aged 10 to 12 as well as those of adults obtained in a previous study. 3.Explore the relation between categorical perception of sounds and the pattern of hemispheric lateralization. Correlation analyses between indices of categorical perception and indices of hemispheric lateralization will be performed in order to test the hypothesis that categorical perception can predict the pattern of hemispheric lateralization. 4.Examine the relationships between phonetic perception and performance on measures of phonological processing and sight reading as well as the relationships between the patterns of brain activation while performing the phonetic perception task and performance on the phonological and reading measures. 5.Investigate the extent to which there is a relationship between developmental changes in the brain activation associated with phonetic perception and developmental progression in the acquisition of phonological processing and reading
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