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Reduced segregation of brain networks in spatial neglect after stroke.

BACKGROUND/PURPOSE
To investigate the association between the severity of spatial neglect and the changes of brain system segregation (i.e., the balance of between-network and within-network communication) after stroke.


METHODS
Twenty acute patients with stroke in the right hemisphere underwent neuropsychological and resting-state functional MRI evaluations. The severity of spatial neglect was quantified using the Center of Cancellation (CoC) scores of the Bells cancellation test. For each patient, resting-state functional connectivity (FC) matrices were assessed by implementing a brain parcellation of nine networks that included the visual, dorsal and ventral attention, sensorimotor, auditory, cingulo-opercular, language, fronto-parietal, and default mode networks. For each patient and each network, we then computed the System Segregation defined as the difference among the within network FC and between network FC (normalized by the within network FC). Finally, for each network, the CoC scores were correlated with the System Segregation.


RESULTS
The correlational analyses revealed a negative relationship between CoC and System Segregation in the dorsal and ventral attention, sensorimotor, and default mode networks (q<0.05 FDR-corrected). Patients with more severe spatial neglect exhibited lower System Segregation and vice versa.


CONCLUSION
The loss of segregation in multiple and specific networks provides a functional framework for the deficits in spatial and non-spatial attention and motor/exploratory ability observed in neglect patients.