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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

Tone contours of the continuum from /ba2/ to /ba4/.Continua 3, 7 and 11 are marked with thick lines.
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pone-0020963-g001: Tone contours of the continuum from /ba2/ to /ba4/.Continua 3, 7 and 11 are marked with thick lines.

Mentions: The stimuli were previously used in an event-related potential (ERP) study [17]. They were chosen from Chinese lexical tonal continuum from the high-rising tone (Tone2) to the falling tone (Tone4) (Fig. 1), which form an across-category stimulus pair (3 and 7) and a within-category stimulus pair (7 and 11). Because the physical intervals between the across-category pair and within-category pair were equated [17], the key difference between the stimulus pairs is that the former involves a change to a different phonological category, while the latter involves only an acoustic change. As in the ERP study, in our fMRI study we used stimulus 7 as the standard stimulus, and stimuli 3 and 11 as the across-category and within-category deviants, respectively.


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)

Tone contours of the continuum from /ba2/ to /ba4/.Continua 3, 7 and 11 are marked with thick lines.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0020963-g001: Tone contours of the continuum from /ba2/ to /ba4/.Continua 3, 7 and 11 are marked with thick lines.
Mentions: The stimuli were previously used in an event-related potential (ERP) study [17]. They were chosen from Chinese lexical tonal continuum from the high-rising tone (Tone2) to the falling tone (Tone4) (Fig. 1), which form an across-category stimulus pair (3 and 7) and a within-category stimulus pair (7 and 11). Because the physical intervals between the across-category pair and within-category pair were equated [17], the key difference between the stimulus pairs is that the former involves a change to a different phonological category, while the latter involves only an acoustic change. As in the ERP study, in our fMRI study we used stimulus 7 as the standard stimulus, and stimuli 3 and 11 as the across-category and within-category deviants, respectively.

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