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Cortical dynamics of acoustic and phonological processing in speech perception.

Zhang L, Xi J, Xu G, Shu H, Wang X, Li P - PLoS ONE (2011)

Bottom Line: We found that relative to within-category variation, across-category variation elicited stronger activation in the left middle MTG (mMTG), apparently reflecting the abstract phonological representations.At the same time, activation in the core auditory region decreased, resulting from the top-down influences of phonological processing.These results support a hierarchical organization of the ventral acoustic-phonological processing stream, which originates in the right HG/STG and projects to the left mMTG.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China.

ABSTRACT
In speech perception, a functional hierarchy has been proposed by recent functional neuroimaging studies: core auditory areas on the dorsal plane of superior temporal gyrus (STG) are sensitive to basic acoustic characteristics, whereas downstream regions, specifically the left superior temporal sulcus (STS) and middle temporal gyrus (MTG) ventral to Heschl's gyrus (HG) are responsive to abstract phonological features. What is unclear so far is the relationship between the dorsal and ventral processes, especially with regard to whether low-level acoustic processing is modulated by high-level phonological processing. To address the issue, we assessed sensitivity of core auditory and downstream regions to acoustic and phonological variations by using within- and across-category lexical tonal continua with equal physical intervals. We found that relative to within-category variation, across-category variation elicited stronger activation in the left middle MTG (mMTG), apparently reflecting the abstract phonological representations. At the same time, activation in the core auditory region decreased, resulting from the top-down influences of phonological processing. These results support a hierarchical organization of the ventral acoustic-phonological processing stream, which originates in the right HG/STG and projects to the left mMTG. Furthermore, our study provides direct evidence that low-level acoustic analysis is modulated by high-level phonological representations, revealing the cortical dynamics of acoustic and phonological processing in speech perception. Our findings confirm the existence of reciprocal progression projections in the auditory pathways and the roles of both feed-forward and feedback mechanisms in speech perception.

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Related in: MedlinePlus

Schematic illustration of the experimental paradigm.
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pone-0020963-g002: Schematic illustration of the experimental paradigm.

Mentions: The experimental design (Fig. 2) was adapted from Tervaniemi et al. 's study [18]. The sounds were presented in blocked design with 1 s stimulus-onset asynchrony (SOA). Three conditions of stimuli were presented in separate blocks and each block consisted of either 30 standard stimuli, a mixed sequence of standard stimuli and across-category deviants, or standard stimuli and within-category deviants. In a mixed sequence, there were six deviants presented in a pseudorandom order among the standard stimuli. Because of demands set by the clustered scanning paradigm, deviant stimuli were never presented in the first, fourth, seventh, etc., position. The experiment consisted of 2 scanning runs, 15 blocks each (5 blocks for each condition), that is, a total of 10 repetitions for each condition of stimuli. Each run was preceded by a 9 s silent baseline to familiarize the participants with the situation.


Cortical dynamics of acoustic and phonological processing in speech perception.

Zhang L, Xi J, Xu G, Shu H, Wang X, Li P - PLoS ONE (2011)

Schematic illustration of the experimental paradigm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3113809&req=5

pone-0020963-g002: Schematic illustration of the experimental paradigm.
Mentions: The experimental design (Fig. 2) was adapted from Tervaniemi et al. 's study [18]. The sounds were presented in blocked design with 1 s stimulus-onset asynchrony (SOA). Three conditions of stimuli were presented in separate blocks and each block consisted of either 30 standard stimuli, a mixed sequence of standard stimuli and across-category deviants, or standard stimuli and within-category deviants. In a mixed sequence, there were six deviants presented in a pseudorandom order among the standard stimuli. Because of demands set by the clustered scanning paradigm, deviant stimuli were never presented in the first, fourth, seventh, etc., position. The experiment consisted of 2 scanning runs, 15 blocks each (5 blocks for each condition), that is, a total of 10 repetitions for each condition of stimuli. Each run was preceded by a 9 s silent baseline to familiarize the participants with the situation.

Bottom Line: We found that relative to within-category variation, across-category variation elicited stronger activation in the left middle MTG (mMTG), apparently reflecting the abstract phonological representations.At the same time, activation in the core auditory region decreased, resulting from the top-down influences of phonological processing.These results support a hierarchical organization of the ventral acoustic-phonological processing stream, which originates in the right HG/STG and projects to the left mMTG.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China.

ABSTRACT
In speech perception, a functional hierarchy has been proposed by recent functional neuroimaging studies: core auditory areas on the dorsal plane of superior temporal gyrus (STG) are sensitive to basic acoustic characteristics, whereas downstream regions, specifically the left superior temporal sulcus (STS) and middle temporal gyrus (MTG) ventral to Heschl's gyrus (HG) are responsive to abstract phonological features. What is unclear so far is the relationship between the dorsal and ventral processes, especially with regard to whether low-level acoustic processing is modulated by high-level phonological processing. To address the issue, we assessed sensitivity of core auditory and downstream regions to acoustic and phonological variations by using within- and across-category lexical tonal continua with equal physical intervals. We found that relative to within-category variation, across-category variation elicited stronger activation in the left middle MTG (mMTG), apparently reflecting the abstract phonological representations. At the same time, activation in the core auditory region decreased, resulting from the top-down influences of phonological processing. These results support a hierarchical organization of the ventral acoustic-phonological processing stream, which originates in the right HG/STG and projects to the left mMTG. Furthermore, our study provides direct evidence that low-level acoustic analysis is modulated by high-level phonological representations, revealing the cortical dynamics of acoustic and phonological processing in speech perception. Our findings confirm the existence of reciprocal progression projections in the auditory pathways and the roles of both feed-forward and feedback mechanisms in speech perception.

Show MeSH
Related in: MedlinePlus