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Broca's area, sentence comprehension, and working memory: an fMRI Study.

Rogalsky C, Matchin W, Hickok G - Front Hum Neurosci (2008)

Bottom Line: A second experiment used fMRI to document the brain regions underlying this effect.However, during concurrent speech articulation (but not finger-tapping) this complexity effect was eliminated in the pars opercularis suggesting that this region supports sentence comprehension via its role in articulatory rehearsal.Activity in the pars triangularis was modulated by the finger-tapping task, but not the speech articulation task.

View Article: PubMed Central - PubMed

Affiliation: Center for Cognitive Neuroscience & Department of Cognitive Sciences, University of California Irvine, USA.

ABSTRACT
The role of Broca's area in sentence processing remains controversial. According to one view, Broca's area is involved in processing a subcomponent of syntactic processing. Another view holds that it contributes to sentence processing via verbal working memory. Sub-regions of Broca's area have been identified that are more active during the processing of complex (object-relative clause) sentences compared to simple (subject-relative clause) sentences. The present study aimed to determine if this complexity effect can be accounted for in terms of the articulatory rehearsal component of verbal working memory. In a behavioral experiment, subjects were asked to comprehend sentences during concurrent speech articulation which minimizes articulatory rehearsal as a resource for sentence comprehension. A finger-tapping task was used as a control concurrent task. Only the object-relative clause sentences were more difficult to comprehend during speech articulation than during the manual task, showing that articulatory rehearsal does contribute to sentence processing. A second experiment used fMRI to document the brain regions underlying this effect. Subjects judged the plausibility of sentences during speech articulation, a finger-tapping task, or without a concurrent task. In the absence of a secondary task, Broca's area (pars triangularis and pars opercularis) demonstrated an increase in activity as a function of syntactic complexity. However, during concurrent speech articulation (but not finger-tapping) this complexity effect was eliminated in the pars opercularis suggesting that this region supports sentence comprehension via its role in articulatory rehearsal. Activity in the pars triangularis was modulated by the finger-tapping task, but not the speech articulation task.

No MeSH data available.


Related in: MedlinePlus

Mean peak amplitudes of the left pars opercularis (A) and left pars triangularis (B) regions more active during the perception of object-relative sentences than during subject-relative sentences (p < 0.005) in the absence of a secondary task, or during one of the concurrent tasks, averaged across trials and subjects. Mean peak amplitudes of each cluster are shown for each sentence type presented during each task condition, as well as for just articulation and finger-tapping alone. Error bars represent 95% confidence intervals. The Talairach coordinates of each cluster's peak are given, and correspond to the contrast maps in Figure 5.
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Figure 7: Mean peak amplitudes of the left pars opercularis (A) and left pars triangularis (B) regions more active during the perception of object-relative sentences than during subject-relative sentences (p < 0.005) in the absence of a secondary task, or during one of the concurrent tasks, averaged across trials and subjects. Mean peak amplitudes of each cluster are shown for each sentence type presented during each task condition, as well as for just articulation and finger-tapping alone. Error bars represent 95% confidence intervals. The Talairach coordinates of each cluster's peak are given, and correspond to the contrast maps in Figure 5.

Mentions: Figure 7 shows mean peak amplitude plots for all conditions within the pars opercularis and pars orbitalis regions identified in the above analyses (i.e., the ROIs shown in Figure 5). Although the pars opercularis and pars triangularis regions identified by the OR > SR contrast during no concurrent task are not the exact same voxels identified by the contrasts during concurrent articulation and finger-tapping, respectively, comparing the mean peak amplitudes for the clusters (i.e. comparing the left and right sides of Figure 7) reveals that they have very similar response properties. Considering the pars opercularis first, it is clear that speech articulation alone activates this region, and does so equally as well as the OR sentences with no concurrent task. Processing OR sentences during speech articulation does not increase activation levels over articulation or OR sentence comprehension alone. However, adding speech articulation to SR sentence comprehension does increase activation levels presumably reflecting a saturation of this region's activity due to the articulation task, as expected. Finally, speech articulation alone produces substantially more activation than performing the finger tapping task alone; finger tapping appears to have no effect on the activation levels in the pars opercularis associated with OR or SR sentence processing. In short, this pattern of results is consistent with the view that activation in this region is driven primarily by speech articulation: activation is maximal during articulation whether sentences are being processed or not (middle set of bars in Figure 7), or during the processing of high load sentences that draw on articulatory rehearsal (OR sentences in left and right sets of bars in Figure 7).


Broca's area, sentence comprehension, and working memory: an fMRI Study.

Rogalsky C, Matchin W, Hickok G - Front Hum Neurosci (2008)

Mean peak amplitudes of the left pars opercularis (A) and left pars triangularis (B) regions more active during the perception of object-relative sentences than during subject-relative sentences (p < 0.005) in the absence of a secondary task, or during one of the concurrent tasks, averaged across trials and subjects. Mean peak amplitudes of each cluster are shown for each sentence type presented during each task condition, as well as for just articulation and finger-tapping alone. Error bars represent 95% confidence intervals. The Talairach coordinates of each cluster's peak are given, and correspond to the contrast maps in Figure 5.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2572210&req=5

Figure 7: Mean peak amplitudes of the left pars opercularis (A) and left pars triangularis (B) regions more active during the perception of object-relative sentences than during subject-relative sentences (p < 0.005) in the absence of a secondary task, or during one of the concurrent tasks, averaged across trials and subjects. Mean peak amplitudes of each cluster are shown for each sentence type presented during each task condition, as well as for just articulation and finger-tapping alone. Error bars represent 95% confidence intervals. The Talairach coordinates of each cluster's peak are given, and correspond to the contrast maps in Figure 5.
Mentions: Figure 7 shows mean peak amplitude plots for all conditions within the pars opercularis and pars orbitalis regions identified in the above analyses (i.e., the ROIs shown in Figure 5). Although the pars opercularis and pars triangularis regions identified by the OR > SR contrast during no concurrent task are not the exact same voxels identified by the contrasts during concurrent articulation and finger-tapping, respectively, comparing the mean peak amplitudes for the clusters (i.e. comparing the left and right sides of Figure 7) reveals that they have very similar response properties. Considering the pars opercularis first, it is clear that speech articulation alone activates this region, and does so equally as well as the OR sentences with no concurrent task. Processing OR sentences during speech articulation does not increase activation levels over articulation or OR sentence comprehension alone. However, adding speech articulation to SR sentence comprehension does increase activation levels presumably reflecting a saturation of this region's activity due to the articulation task, as expected. Finally, speech articulation alone produces substantially more activation than performing the finger tapping task alone; finger tapping appears to have no effect on the activation levels in the pars opercularis associated with OR or SR sentence processing. In short, this pattern of results is consistent with the view that activation in this region is driven primarily by speech articulation: activation is maximal during articulation whether sentences are being processed or not (middle set of bars in Figure 7), or during the processing of high load sentences that draw on articulatory rehearsal (OR sentences in left and right sets of bars in Figure 7).

Bottom Line: A second experiment used fMRI to document the brain regions underlying this effect.However, during concurrent speech articulation (but not finger-tapping) this complexity effect was eliminated in the pars opercularis suggesting that this region supports sentence comprehension via its role in articulatory rehearsal.Activity in the pars triangularis was modulated by the finger-tapping task, but not the speech articulation task.

View Article: PubMed Central - PubMed

Affiliation: Center for Cognitive Neuroscience & Department of Cognitive Sciences, University of California Irvine, USA.

ABSTRACT
The role of Broca's area in sentence processing remains controversial. According to one view, Broca's area is involved in processing a subcomponent of syntactic processing. Another view holds that it contributes to sentence processing via verbal working memory. Sub-regions of Broca's area have been identified that are more active during the processing of complex (object-relative clause) sentences compared to simple (subject-relative clause) sentences. The present study aimed to determine if this complexity effect can be accounted for in terms of the articulatory rehearsal component of verbal working memory. In a behavioral experiment, subjects were asked to comprehend sentences during concurrent speech articulation which minimizes articulatory rehearsal as a resource for sentence comprehension. A finger-tapping task was used as a control concurrent task. Only the object-relative clause sentences were more difficult to comprehend during speech articulation than during the manual task, showing that articulatory rehearsal does contribute to sentence processing. A second experiment used fMRI to document the brain regions underlying this effect. Subjects judged the plausibility of sentences during speech articulation, a finger-tapping task, or without a concurrent task. In the absence of a secondary task, Broca's area (pars triangularis and pars opercularis) demonstrated an increase in activity as a function of syntactic complexity. However, during concurrent speech articulation (but not finger-tapping) this complexity effect was eliminated in the pars opercularis suggesting that this region supports sentence comprehension via its role in articulatory rehearsal. Activity in the pars triangularis was modulated by the finger-tapping task, but not the speech articulation task.

No MeSH data available.


Related in: MedlinePlus