Disrupted integration-segregation balance in the intact hemisphere in chronic spatial neglect

Area of Science:

• Neuroscience
• Cognitive Neurology
• Neuroimaging

Background:

• Spatial neglect, a common deficit post-right hemisphere stroke, involves impaired attention to the left side of space.
• Persistence of neglect is linked to right frontoparietal dysfunction and interhemispheric imbalances, but left hemisphere reorganization is poorly understood.

Purpose of the Study:

• To investigate macroscale functional reorganization in the non-lesioned left hemisphere of patients with chronic spatial neglect using functional connectivity gradient analysis.
• To explore the relationship between these functional changes, neglect severity, and structural integrity of white matter tracts.

Main Methods:

• Resting-state functional magnetic resonance imaging (fMRI) was used to analyze functional connectivity gradients in patients with chronic left spatial neglect.
• Gradient analysis quantified network segregation and the unimodal-to-transmodal hierarchy.
• Structural integrity of the left inferior fronto-occipital fasciculus (IFOF) was assessed.

Main Results:

• Abnormal network segregation in left frontoparietal and default mode networks correlated with neglect severity and attentional bias.
• The unimodal-to-transmodal hierarchy gradient was associated with neglect severity.
• Altered gradients within the frontoparietal control network were observed in neglect patients, with 11 of 13 showing this pattern.

Conclusions:

• Spatial neglect pathophysiology involves maladaptive dominance and reorganization within the non-lesioned left hemisphere's intrinsic architecture.
• Findings suggest neglect emerges from large-scale network imbalance, impacting diagnosis and intervention strategies.
• This work provides a new framework for understanding neglect and its implications for hemispheric asymmetry and consciousness models.