The Reorganization of Cerebellar Functional Network Topology in Post-stroke Aphasia: A Resting-State fMRI Study.

Small-world organization was preserved in both PSA patients and healthy controls, but PSA patients showed significant reductions in small-world network metrics.

• 73 right-handed PSA patients and 75 matched healthy controls underwent 3T resting-state fMRI
• PSA patients showed significant reductions in the small-world index, clustering coefficient, and local efficiency compared to healthy controls
• These reductions indicate impaired network segregation and local processing in the cerebellar functional network
• The cerebellum was parcellated using the Seitzman-27 atlas, which assigns cerebellar ROIs to canonical large-scale networks

Nodal analysis revealed opposing changes in degree centrality across cerebellar subnetworks in PSA patients.

• Decreased degree centrality was found in the frontoparietal network cerebellar regions
• Increased degree centrality was found in the dorsal somatomotor network cerebellar regions
• These nodal changes suggest a reorganization of hub structure within the cerebellar functional network in PSA

Functional connectivity was reduced within default mode and frontoparietal cerebellar network regions, while connectivity between frontoparietal and dorsal somatomotor regions increased in PSA.

• Reduced functional connectivity was observed within the default mode network cerebellar regions
• Reduced functional connectivity was also observed within the frontoparietal network cerebellar regions
• Increased functional connectivity was found between frontoparietal and dorsal somatomotor cerebellar regions
• All functional connectivity findings were FDR-corrected

Lower cerebellar network clustering coefficient and local efficiency were associated with poorer language and cognitive performance in PSA patients.

• Lower clustering coefficient was associated with poorer auditory comprehension, memory, and reasoning
• Lower local efficiency was associated with poorer auditory comprehension, memory, and reasoning
• These associations extended across both language-specific (auditory comprehension) and non-language cognitive domains (memory and reasoning)

Lesion volume was associated with worse language and cognitive outcomes but was not associated with global cerebellar network measures after covariate adjustment.

• Lesion volume showed associations with worse language and cognitive performance outcomes
• After covariate adjustment, lesion volume was not significantly associated with global cerebellar network topological measures
• This dissociation suggests cerebellar network topology captures variance in clinical outcomes beyond that explained by lesion volume alone

The cerebellar functional network was characterized using a network-specific parcellation approach allowing assignment of cerebellar regions to canonical large-scale brain networks.

• The Seitzman-27 atlas was used to parcellate the cerebellum into regions of interest
• This atlas assigns cerebellar ROIs to canonical large-scale networks including the frontoparietal network, default mode network, and dorsal somatomotor network
• Global and nodal topological metrics as well as ROI-to-ROI functional connectivity were quantified
• Relationships between network measures and both language and non-language cognition were assessed