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Greater BOLD variability in older compared with younger adults during audiovisual speech perception.

Baum SH, Beauchamp MS - PLoS ONE (2014)

Bottom Line: While mean response amplitudes were moderately greater in younger adults, older adults had much greater within-subject variability.The greatly increased variability in older adults was observed for both individual voxels in the whole-brain analysis and for ROIs in the left superior temporal sulcus, the left auditory cortex, and the left visual cortex.Increased variability in older adults could not be attributed to differences in head movements between the groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas, United States of America; Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, United States of America.

ABSTRACT
Older adults exhibit decreased performance and increased trial-to-trial variability on a range of cognitive tasks, including speech perception. We used blood oxygen level dependent functional magnetic resonance imaging (BOLD fMRI) to search for neural correlates of these behavioral phenomena. We compared brain responses to simple speech stimuli (audiovisual syllables) in 24 healthy older adults (53 to 70 years old) and 14 younger adults (23 to 39 years old) using two independent analysis strategies: region-of-interest (ROI) and voxel-wise whole-brain analysis. While mean response amplitudes were moderately greater in younger adults, older adults had much greater within-subject variability. The greatly increased variability in older adults was observed for both individual voxels in the whole-brain analysis and for ROIs in the left superior temporal sulcus, the left auditory cortex, and the left visual cortex. Increased variability in older adults could not be attributed to differences in head movements between the groups. Increased neural variability may be related to the performance declines and increased behavioral variability that occur with aging.

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Whole-brain analysis of differences in intrasubject variability, response amplitude, and intersubject variability in older and younger adults.A: Regions that show a significant positive response (t >2 for all audiovisual syllables vs. baseline) to audiovisual speech in both older and younger adults. L: left hemisphere, R: right hemisphere. B: Differences in intrasubject variability (variability of the amplitude of the BOLD response to audiovisual speech within each subject) between older and younger subjects, masked by active regions in (A). Orange regions indicate areas with greater intrasubject variability in older adults. C: Differences in response amplitude. Green regions indicate no difference in response amplitude; blue regions indicate areas of greater response amplitude in younger adults. D: Differences in intersubject variability (variability of the amplitude of the BOLD response across subjects). Orange regions indicate areas with greater response variability in older adults.
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pone-0111121-g003: Whole-brain analysis of differences in intrasubject variability, response amplitude, and intersubject variability in older and younger adults.A: Regions that show a significant positive response (t >2 for all audiovisual syllables vs. baseline) to audiovisual speech in both older and younger adults. L: left hemisphere, R: right hemisphere. B: Differences in intrasubject variability (variability of the amplitude of the BOLD response to audiovisual speech within each subject) between older and younger subjects, masked by active regions in (A). Orange regions indicate areas with greater intrasubject variability in older adults. C: Differences in response amplitude. Green regions indicate no difference in response amplitude; blue regions indicate areas of greater response amplitude in younger adults. D: Differences in intersubject variability (variability of the amplitude of the BOLD response across subjects). Orange regions indicate areas with greater response variability in older adults.

Mentions: Our first set of analyses was limited to our three a priori ROIs created using block-design localizers. To overcome this limitation, and to prevent any biases introduced by slight differences in the localizers between old and young subjects, our second set of analyses examined the entire brain. First, we selected all voxels that showed a significant positive response (t >2 for all audiovisual syllables vs. baseline) to audiovisual syllables across old and young subjects (Table 1 and Figure 3A).


Greater BOLD variability in older compared with younger adults during audiovisual speech perception.

Baum SH, Beauchamp MS - PLoS ONE (2014)

Whole-brain analysis of differences in intrasubject variability, response amplitude, and intersubject variability in older and younger adults.A: Regions that show a significant positive response (t >2 for all audiovisual syllables vs. baseline) to audiovisual speech in both older and younger adults. L: left hemisphere, R: right hemisphere. B: Differences in intrasubject variability (variability of the amplitude of the BOLD response to audiovisual speech within each subject) between older and younger subjects, masked by active regions in (A). Orange regions indicate areas with greater intrasubject variability in older adults. C: Differences in response amplitude. Green regions indicate no difference in response amplitude; blue regions indicate areas of greater response amplitude in younger adults. D: Differences in intersubject variability (variability of the amplitude of the BOLD response across subjects). Orange regions indicate areas with greater response variability in older adults.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4206517&req=5

pone-0111121-g003: Whole-brain analysis of differences in intrasubject variability, response amplitude, and intersubject variability in older and younger adults.A: Regions that show a significant positive response (t >2 for all audiovisual syllables vs. baseline) to audiovisual speech in both older and younger adults. L: left hemisphere, R: right hemisphere. B: Differences in intrasubject variability (variability of the amplitude of the BOLD response to audiovisual speech within each subject) between older and younger subjects, masked by active regions in (A). Orange regions indicate areas with greater intrasubject variability in older adults. C: Differences in response amplitude. Green regions indicate no difference in response amplitude; blue regions indicate areas of greater response amplitude in younger adults. D: Differences in intersubject variability (variability of the amplitude of the BOLD response across subjects). Orange regions indicate areas with greater response variability in older adults.
Mentions: Our first set of analyses was limited to our three a priori ROIs created using block-design localizers. To overcome this limitation, and to prevent any biases introduced by slight differences in the localizers between old and young subjects, our second set of analyses examined the entire brain. First, we selected all voxels that showed a significant positive response (t >2 for all audiovisual syllables vs. baseline) to audiovisual syllables across old and young subjects (Table 1 and Figure 3A).

Bottom Line: While mean response amplitudes were moderately greater in younger adults, older adults had much greater within-subject variability.The greatly increased variability in older adults was observed for both individual voxels in the whole-brain analysis and for ROIs in the left superior temporal sulcus, the left auditory cortex, and the left visual cortex.Increased variability in older adults could not be attributed to differences in head movements between the groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas, United States of America; Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, United States of America.

ABSTRACT
Older adults exhibit decreased performance and increased trial-to-trial variability on a range of cognitive tasks, including speech perception. We used blood oxygen level dependent functional magnetic resonance imaging (BOLD fMRI) to search for neural correlates of these behavioral phenomena. We compared brain responses to simple speech stimuli (audiovisual syllables) in 24 healthy older adults (53 to 70 years old) and 14 younger adults (23 to 39 years old) using two independent analysis strategies: region-of-interest (ROI) and voxel-wise whole-brain analysis. While mean response amplitudes were moderately greater in younger adults, older adults had much greater within-subject variability. The greatly increased variability in older adults was observed for both individual voxels in the whole-brain analysis and for ROIs in the left superior temporal sulcus, the left auditory cortex, and the left visual cortex. Increased variability in older adults could not be attributed to differences in head movements between the groups. Increased neural variability may be related to the performance declines and increased behavioral variability that occur with aging.

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