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A comprehensive assessment of resting state networks: bidirectional modification of functional integrity in cerebro-cerebellar networks in dementia.

Castellazzi G, Palesi F, Casali S, Vitali P, Sinforiani E, Wheeler-Kingshott CA, D'Angelo E - Front Neurosci (2014)

Bottom Line: The cerebellum showed a unique behavior where voxels of decreased gFC were only found in AD while a significant gFC increase was only found in MCI.In conclusion, this analysis revealed that the DMN was affected by remarkable FC increases, that FC alterations extended over several RSNs, that derangement of functional relationships between multiple areas occurred already in the early stages of dementia.These results warrant future work to verify whether these represent compensatory mechanisms that exploit a pre-existing neural reserve through plasticity, which evolve in a state of lack of connectivity between different networks with the worsening of the pathology.

View Article: PubMed Central - PubMed

Affiliation: Department of Industrial and Information Engineering, University of Pavia Pavia, Italy ; Brain Connectivity Center, C. Mondino National Neurological Institute Pavia, Italy.

ABSTRACT
In resting state fMRI (rs-fMRI), only functional connectivity (FC) reductions in the default mode network (DMN) are normally reported as a biomarker for Alzheimer's disease (AD). In this investigation we have developed a comprehensive strategy to characterize the FC changes occurring in multiple networks and applied it in a pilot study of subjects with AD and Mild Cognitive Impairment (MCI), compared to healthy controls (HC). Resting state networks (RSNs) were studied in 14 AD (70 ± 6 years), 12 MCI (74 ± 6 years), and 16 HC (69 ± 5 years). RSN alterations were present in almost all the 15 recognized RSNs; overall, 474 voxels presented a reduced FC in MCI and 1244 in AD while 1627 voxels showed an increased FC in MCI and 1711 in AD. The RSNs were then ranked according to the magnitude and extension of FC changes (gFC), putting in evidence 6 RSNs with prominent changes: DMN, frontal cortical network (FCN), lateral visual network (LVN), basal ganglia network (BGN), cerebellar network (CBLN), and the anterior insula network (AIN). Nodes, or hubs, showing alterations common to more than one RSN were mostly localized within the prefrontal cortex and the mesial-temporal cortex. The cerebellum showed a unique behavior where voxels of decreased gFC were only found in AD while a significant gFC increase was only found in MCI. The gFC alterations showed strong correlations (p < 0.001) with psychological scores, in particular Mini-Mental State Examination (MMSE) and attention/memory tasks. In conclusion, this analysis revealed that the DMN was affected by remarkable FC increases, that FC alterations extended over several RSNs, that derangement of functional relationships between multiple areas occurred already in the early stages of dementia. These results warrant future work to verify whether these represent compensatory mechanisms that exploit a pre-existing neural reserve through plasticity, which evolve in a state of lack of connectivity between different networks with the worsening of the pathology.

No MeSH data available.


Related in: MedlinePlus

Ranking of gFC changes in MCI and AD. In order to better identify the patterns of gFC changes within the networks, for each contrast (MCI < HC, MCI > HC on the top; AD < HC, AD > HC on the bottom of the picture) we ranked the RSN alterations in terms of their decreasing gFC. We identified 6 different prototypical patterns: (1) FCN (green arrows) showed the largest gFC reduction, both in AD and MCI, and no increase in any conditions; (2) AIN (turquoise arrows) showed no gFC reduction, either in AD or MCI, but it showed a large increase in both conditions; (3) DMN (blue arrows) showed the second largest gFC reduction, both in AD and MCI, but at the same time it showed also the largest increase in both conditions; (4) BGN (orange arrows) shows a reduction in AD but not in MCI, while it also shows an increase in both cases; (5) CBLN (magenta arrows) shows just a minor decrease in AD but a remarkable increase in MCI only; (6) LVN (yellow arrow) shows gFC increase in both AD and MCI, with stronger effect in AD. At the same time it showed a small gFC reduction in MCI, but not in AD.
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Figure 4: Ranking of gFC changes in MCI and AD. In order to better identify the patterns of gFC changes within the networks, for each contrast (MCI < HC, MCI > HC on the top; AD < HC, AD > HC on the bottom of the picture) we ranked the RSN alterations in terms of their decreasing gFC. We identified 6 different prototypical patterns: (1) FCN (green arrows) showed the largest gFC reduction, both in AD and MCI, and no increase in any conditions; (2) AIN (turquoise arrows) showed no gFC reduction, either in AD or MCI, but it showed a large increase in both conditions; (3) DMN (blue arrows) showed the second largest gFC reduction, both in AD and MCI, but at the same time it showed also the largest increase in both conditions; (4) BGN (orange arrows) shows a reduction in AD but not in MCI, while it also shows an increase in both cases; (5) CBLN (magenta arrows) shows just a minor decrease in AD but a remarkable increase in MCI only; (6) LVN (yellow arrow) shows gFC increase in both AD and MCI, with stronger effect in AD. At the same time it showed a small gFC reduction in MCI, but not in AD.

Mentions: In order to better identify the patterns of alterations within the RSNs, we assessed the behavior of the gFC index for each of the four contrasts. Results, which are summarized in Figure 4, lead to the identification of 6 RSN with prototypical patterns:


A comprehensive assessment of resting state networks: bidirectional modification of functional integrity in cerebro-cerebellar networks in dementia.

Castellazzi G, Palesi F, Casali S, Vitali P, Sinforiani E, Wheeler-Kingshott CA, D'Angelo E - Front Neurosci (2014)

Ranking of gFC changes in MCI and AD. In order to better identify the patterns of gFC changes within the networks, for each contrast (MCI < HC, MCI > HC on the top; AD < HC, AD > HC on the bottom of the picture) we ranked the RSN alterations in terms of their decreasing gFC. We identified 6 different prototypical patterns: (1) FCN (green arrows) showed the largest gFC reduction, both in AD and MCI, and no increase in any conditions; (2) AIN (turquoise arrows) showed no gFC reduction, either in AD or MCI, but it showed a large increase in both conditions; (3) DMN (blue arrows) showed the second largest gFC reduction, both in AD and MCI, but at the same time it showed also the largest increase in both conditions; (4) BGN (orange arrows) shows a reduction in AD but not in MCI, while it also shows an increase in both cases; (5) CBLN (magenta arrows) shows just a minor decrease in AD but a remarkable increase in MCI only; (6) LVN (yellow arrow) shows gFC increase in both AD and MCI, with stronger effect in AD. At the same time it showed a small gFC reduction in MCI, but not in AD.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4115623&req=5

Figure 4: Ranking of gFC changes in MCI and AD. In order to better identify the patterns of gFC changes within the networks, for each contrast (MCI < HC, MCI > HC on the top; AD < HC, AD > HC on the bottom of the picture) we ranked the RSN alterations in terms of their decreasing gFC. We identified 6 different prototypical patterns: (1) FCN (green arrows) showed the largest gFC reduction, both in AD and MCI, and no increase in any conditions; (2) AIN (turquoise arrows) showed no gFC reduction, either in AD or MCI, but it showed a large increase in both conditions; (3) DMN (blue arrows) showed the second largest gFC reduction, both in AD and MCI, but at the same time it showed also the largest increase in both conditions; (4) BGN (orange arrows) shows a reduction in AD but not in MCI, while it also shows an increase in both cases; (5) CBLN (magenta arrows) shows just a minor decrease in AD but a remarkable increase in MCI only; (6) LVN (yellow arrow) shows gFC increase in both AD and MCI, with stronger effect in AD. At the same time it showed a small gFC reduction in MCI, but not in AD.
Mentions: In order to better identify the patterns of alterations within the RSNs, we assessed the behavior of the gFC index for each of the four contrasts. Results, which are summarized in Figure 4, lead to the identification of 6 RSN with prototypical patterns:

Bottom Line: The cerebellum showed a unique behavior where voxels of decreased gFC were only found in AD while a significant gFC increase was only found in MCI.In conclusion, this analysis revealed that the DMN was affected by remarkable FC increases, that FC alterations extended over several RSNs, that derangement of functional relationships between multiple areas occurred already in the early stages of dementia.These results warrant future work to verify whether these represent compensatory mechanisms that exploit a pre-existing neural reserve through plasticity, which evolve in a state of lack of connectivity between different networks with the worsening of the pathology.

View Article: PubMed Central - PubMed

Affiliation: Department of Industrial and Information Engineering, University of Pavia Pavia, Italy ; Brain Connectivity Center, C. Mondino National Neurological Institute Pavia, Italy.

ABSTRACT
In resting state fMRI (rs-fMRI), only functional connectivity (FC) reductions in the default mode network (DMN) are normally reported as a biomarker for Alzheimer's disease (AD). In this investigation we have developed a comprehensive strategy to characterize the FC changes occurring in multiple networks and applied it in a pilot study of subjects with AD and Mild Cognitive Impairment (MCI), compared to healthy controls (HC). Resting state networks (RSNs) were studied in 14 AD (70 ± 6 years), 12 MCI (74 ± 6 years), and 16 HC (69 ± 5 years). RSN alterations were present in almost all the 15 recognized RSNs; overall, 474 voxels presented a reduced FC in MCI and 1244 in AD while 1627 voxels showed an increased FC in MCI and 1711 in AD. The RSNs were then ranked according to the magnitude and extension of FC changes (gFC), putting in evidence 6 RSNs with prominent changes: DMN, frontal cortical network (FCN), lateral visual network (LVN), basal ganglia network (BGN), cerebellar network (CBLN), and the anterior insula network (AIN). Nodes, or hubs, showing alterations common to more than one RSN were mostly localized within the prefrontal cortex and the mesial-temporal cortex. The cerebellum showed a unique behavior where voxels of decreased gFC were only found in AD while a significant gFC increase was only found in MCI. The gFC alterations showed strong correlations (p < 0.001) with psychological scores, in particular Mini-Mental State Examination (MMSE) and attention/memory tasks. In conclusion, this analysis revealed that the DMN was affected by remarkable FC increases, that FC alterations extended over several RSNs, that derangement of functional relationships between multiple areas occurred already in the early stages of dementia. These results warrant future work to verify whether these represent compensatory mechanisms that exploit a pre-existing neural reserve through plasticity, which evolve in a state of lack of connectivity between different networks with the worsening of the pathology.

No MeSH data available.


Related in: MedlinePlus