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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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Mean and standard deviation of BOLD responses to audiovisual speech within subjects.A: Hemodynamic response in the left STS of a single older adult (subject JI). Error bars indicate standard deviation of the response within that subject (intrasubject variability) at each time point. The variability at the 4-second and 6-second time points (bold error bars) was used for group analysis. Representative single subject chosen as the subject whose standard deviation was closest to the mean standard deviation for all older subjects. B: Hemodynamic response in the left STS of a single younger adult (subject HU). Representative single subject chosen as the subject whose standard deviation was closest to the mean standard deviation for all younger subjects. C: Scatter plot of age vs. within-subject standard deviation of the STS response. Blue symbols represent younger adults (n = 14), red symbols represent older adults (n = 19). The lines show the mean of the within-subject standard deviation across each group. The brackets show the results of an unpaired t-test between the within-subject standard deviation in each group. D: Scatter plot of age vs. within-subject standard deviation of the left auditory cortex response. E: Scatter plot of age vs. within-subject standard deviation of the left visual cortex response.
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pone-0111121-g001: Mean and standard deviation of BOLD responses to audiovisual speech within subjects.A: Hemodynamic response in the left STS of a single older adult (subject JI). Error bars indicate standard deviation of the response within that subject (intrasubject variability) at each time point. The variability at the 4-second and 6-second time points (bold error bars) was used for group analysis. Representative single subject chosen as the subject whose standard deviation was closest to the mean standard deviation for all older subjects. B: Hemodynamic response in the left STS of a single younger adult (subject HU). Representative single subject chosen as the subject whose standard deviation was closest to the mean standard deviation for all younger subjects. C: Scatter plot of age vs. within-subject standard deviation of the STS response. Blue symbols represent younger adults (n = 14), red symbols represent older adults (n = 19). The lines show the mean of the within-subject standard deviation across each group. The brackets show the results of an unpaired t-test between the within-subject standard deviation in each group. D: Scatter plot of age vs. within-subject standard deviation of the left auditory cortex response. E: Scatter plot of age vs. within-subject standard deviation of the left visual cortex response.

Mentions: The left STS showed a robust hemodynamic response to audiovisual syllables that was similar in amplitude in individual older and younger subjects. An important behavioral difference in many behavioral paradigms between older and younger subjects is the variability across trials within individual subjects (intrasubject variability). To search for a neural correlate of this phenomenon, we calculated the hemodynamic response function in each subject in every voxel and then measured the standard deviation across trials at each time point in the hemodynamic response within each subject (plotting them as error bars around the mean at each time point). As shown in Figure 1A and 1B, while the response amplitudes were similar for individual older and younger subjects, the variability at each time point of the response was much larger in the older subject.


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

Baum SH, Beauchamp MS - PLoS ONE (2014)

Mean and standard deviation of BOLD responses to audiovisual speech within subjects.A: Hemodynamic response in the left STS of a single older adult (subject JI). Error bars indicate standard deviation of the response within that subject (intrasubject variability) at each time point. The variability at the 4-second and 6-second time points (bold error bars) was used for group analysis. Representative single subject chosen as the subject whose standard deviation was closest to the mean standard deviation for all older subjects. B: Hemodynamic response in the left STS of a single younger adult (subject HU). Representative single subject chosen as the subject whose standard deviation was closest to the mean standard deviation for all younger subjects. C: Scatter plot of age vs. within-subject standard deviation of the STS response. Blue symbols represent younger adults (n = 14), red symbols represent older adults (n = 19). The lines show the mean of the within-subject standard deviation across each group. The brackets show the results of an unpaired t-test between the within-subject standard deviation in each group. D: Scatter plot of age vs. within-subject standard deviation of the left auditory cortex response. E: Scatter plot of age vs. within-subject standard deviation of the left visual cortex response.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0111121-g001: Mean and standard deviation of BOLD responses to audiovisual speech within subjects.A: Hemodynamic response in the left STS of a single older adult (subject JI). Error bars indicate standard deviation of the response within that subject (intrasubject variability) at each time point. The variability at the 4-second and 6-second time points (bold error bars) was used for group analysis. Representative single subject chosen as the subject whose standard deviation was closest to the mean standard deviation for all older subjects. B: Hemodynamic response in the left STS of a single younger adult (subject HU). Representative single subject chosen as the subject whose standard deviation was closest to the mean standard deviation for all younger subjects. C: Scatter plot of age vs. within-subject standard deviation of the STS response. Blue symbols represent younger adults (n = 14), red symbols represent older adults (n = 19). The lines show the mean of the within-subject standard deviation across each group. The brackets show the results of an unpaired t-test between the within-subject standard deviation in each group. D: Scatter plot of age vs. within-subject standard deviation of the left auditory cortex response. E: Scatter plot of age vs. within-subject standard deviation of the left visual cortex response.
Mentions: The left STS showed a robust hemodynamic response to audiovisual syllables that was similar in amplitude in individual older and younger subjects. An important behavioral difference in many behavioral paradigms between older and younger subjects is the variability across trials within individual subjects (intrasubject variability). To search for a neural correlate of this phenomenon, we calculated the hemodynamic response function in each subject in every voxel and then measured the standard deviation across trials at each time point in the hemodynamic response within each subject (plotting them as error bars around the mean at each time point). As shown in Figure 1A and 1B, while the response amplitudes were similar for individual older and younger subjects, the variability at each time point of the response was much larger in the older subject.

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.

Show MeSH