Interestingly, this

age-related difference in connectivit

Interestingly, this

age-related difference in connectivity was not noted in the left hemisphere. This may suggest that the disruption in the default network by age might be more of a unilateral process than a bilateral one. Some task-based fMRI studies have already reported hemispheric asymmetry alteration of brain activity by age during the task performance (Cabeza 2002), and resting-state cerebral blood flow (Lu et al. 2011). However, to the best of our knowledge it has not been reported for DMN using resting-state BOLD fMRI data. We also compared our results with those obtained using the prevailing method in Inhibitors,research,lifescience,medical SMP8, which involves the typical spatial normalization by coregistering to MNI152 template and utilizing a set of predefined Inhibitors,research,lifescience,medical regional mask as the ROI across all the subjects in the study. However, utilization of data-driven atlases has gained popularity in recent years. They generate group-specific templates, and then a single standard space is derived from

those templates. Spatial normalization in this case is done in two steps, first Inhibitors,research,lifescience,medical nonlinear registration to group-specific template and then to the standard space template. This can certainly improve the accuracy of the nonlinear registration. However, utilization of highly accurate nonlinear registration for spatial normalization is hampered by overfitting problem. That is why most of the existing software packages (SPM, selleck analysis of functional neuroimages, FSL, etc.) use a mild or moderate level of nonlinear registration in their spatial normalization. In either case, www.selleckchem.com/products/Rapamycin.html comparing the effectiveness of our approach to normalization with different atlas (data-driven or standard) is beyond the scope of this study, as our native space method totally eliminates the need for spatial Inhibitors,research,lifescience,medical normalization. The standard method produced three significant findings that did not survive Bonferroni correction and did not agree with any of the findings obtained with the new native space method. Only the change Inhibitors,research,lifescience,medical between one region pair (Hi, MOF) was found to be marginally

significant in the same hemisphere (left) in the native space analysis. Figure 6 also shows that spatial smoothing reduces the overall Anacetrapib mean of the pair-wise correlations between the DMN nodes. The fact that we did not detect any significant changes after Bonferroni correction in elders’ DMN functional connectivity using SPM8 should not be surprising as many existing studies of age-related change in DMN have also failed to detect this difference (Bluhm et al. 2008; Beason-Held et al. 2009; Koch et al. 2010). Erroneous spatial normalization accompanied by strong spatial smoothing can simply cause a blending effect across regions which can deteriorate the contrast of the interregional functional connectivity between two groups. There are growing numbers of studies that consider the decline in functional connectivity in DMN as biomarker/hallmark of age-related cognitive decline.

Leave a Reply

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>