Correlation coefficients between a priori seed and target regions that comprise a large-scale brain system (the default network) are quantified for each group, with values significantly different from zero highlighted in bold (mPFC versus PHC: p
Figure 4. Whole-Brain Exploratory Analyses Reveal Widespread…
Figure 4. Whole-Brain Exploratory Analyses Reveal Widespread Correlation Reductions in Aging
Whole-brain analyses of functional…
Figure 4. Whole-Brain Exploratory Analyses Reveal Widespread Correlation Reductions in Aging Whole-brain analyses of functional correlations between the seed region and each voxel across the entire brain are graphically overlaid on a combined young and old adult anatomical image. (A) For a seed placed in the mPFC, positive correlations with the mPFC time course exceeding a threshold of r = 0.1 are colored in red to yellow and averaged for all young participants (top) and all old participants (middle). A direct comparison between the two groups using the young-old contrast (bottom) highlights voxels at a significance level of p < 0.01. The young group shows higher correlations with many regions comprising the network. (B) The reverse scenario when a seed is placed in the pC/rsp. Functional correlations between the pC/rsp and both the mPFC and the bilateral LatPar, as well as some hint of the HF, decline in old age.
Figure 5. Reduced Functional Correlations Are Present…
Figure 5. Reduced Functional Correlations Are Present in the Dorsal Attention System
Correlation coefficients between…
Figure 5. Reduced Functional Correlations Are Present in the Dorsal Attention System Correlation coefficients between a priori seed and target regions that comprise the dorsal attention system are quantified for each group, with values significantly different from zero highlighted in bold (all: p +). The mean variance, computed as the mean of the within-subject variances for each participant’s time course within each region, is also listed at the bottom of the table. **Group t test significant at a Bonferroni corrected alpha of 0.005. *Group t test significant at a Bonferroni corrected alpha of 0.005. *Significant at an uncorrected alpha of 0.05.
Figure 6. Functional Correlations between the Left…
Figure 6. Functional Correlations between the Left and Right Visual Cortex Are Preserved in Aging
Figure 6. Functional Correlations between the Left and Right Visual Cortex Are Preserved in Aging (A) The time course was extracted from a region within the right visual cortex (see inset in [B]) and correlated with the time course extracted from the left visual cortex for each participant. The resulting correlation coefficients are plotted against age. The black regression line, used here for illustrative purposes only, suggests that interhemispheric functional correlations in visual cortex remain constant with age. The green regression line illustrates the same effect in the older group alone (r = −0.17, p = 0.22). (B) Exploratory analyses for a seed in the right visual cortex (see inset) are plotted along a line connecting the center of the right and left visual cortex. For each voxel positioned along the x axis, the mean z-transformed correlation of all young adults is shown in black, and the mean z-transformed correlation of all old adults is shown in green. The rightward z-transformed correlation coefficient peak represents functional correlations at the seed (right visual cortex), and the leftward peak represents functional correlations at the target (left visual cortex). Error bars = SEM.
Figure 7. Functional Correlations Relate to White…
Figure 7. Functional Correlations Relate to White Matter Integrity in Older Adults
Figure 7. Functional Correlations Relate to White Matter Integrity in Older Adults (A) Mean anisotropy for a white matter region shown in yellow on one transverse slice was extracted for each participant. The correlation coefficients resulting from correlating the mPFC and pC/rsp time course are plotted against the mean anisotropy (Aσ) (r = 0.39, p < 0.05). (B) A linear regression was performed using the same measures, after controlling for the effect of age on each measure. When doing so, the strength of the relationship between the anterior-posterior functional correlations and white matter integrity remained significant (partial r = 0.33, p < 0.05).
Figure 8. Functional Correlations Relate to Cognitive…
Figure 8. Functional Correlations Relate to Cognitive Performance in Older Adults
Figure 8. Functional Correlations Relate to Cognitive Performance in Older Adults (A) The z-transformed correlation coefficients resulting from correlating the mPFC and pC/rsp time course is plotted against the cognitive test scores (converted to z-scores) for three different cognitive components (see text for details). The regression lines between the two measures are plotted on each graph. The memory component significantly associates with anterior-posterior functional correlations (executive: r = 0.26, p = 0.11; memory: r = 0.48, p < 0.01; speed: r = 0.24, p = 0.14). (B) A linear regression was performed using the same measures as in (A), after controlling for the effect of age on each measure. When doing so, anterior-posterior functional correlations significantly associated with all three cognitive components (executive: partial r = 0.41, p < 0.01; memory: partial r = 0.40, p < 0.01; speed: r = 0.35, p < 0.05).