Bilateral functional connectivity at rest predicts apraxic symptoms after left hemisphere stroke

Area of Science:

• Neuroscience
• Cognitive Neurology
• Neuroimaging

Background:

• Focal stroke lesions alter functional brain network connectivity.
• Interhemispheric functional connectivity is vital for motor recovery and attention post-stroke.
• The role of interhemispheric connectivity in cognitive functions like praxis remains less understood.

Purpose of the Study:

• To investigate the relationship between apraxia symptoms and resting-state functional MRI connectivity in chronic stroke patients.
• To explore how interhemispheric functional connectivity relates to distinct measures of apraxia, including tool use pantomime accuracy and competing action difficulties.
• To determine the predictive value of functional connectivity and lesion location on apraxia severity.

Main Methods:

• Utilized functional MRI to assess resting-state brain activity in left hemisphere stroke patients and controls.
• Employed a data-driven approach to identify regions-of-interest (ROIs) showing correlations between functional connectivity and apraxia measures.
• Analyzed pairwise functional connectivity within 32 ROIs, controlling for age, head motion, and lesion volume.

Main Results:

• Stronger interhemispheric functional connectivity correlated with better performance on both overall tool use pantomime and reduced difficulty with competing actions.
• Right hemisphere regions homologous to left hemisphere action areas were implicated.
• Weakened functional connectivity in left-lateralized, peri-Sylvian regions was associated with disproportionate difficulty in pantomiming competing tool uses.
• A predictive model combining lesion location and functional connectivity best explained patient performance, with connectivity offering unique predictive variance.

Conclusions:

• Interhemispheric functional connectivity plays a significant role in praxis, even for this strongly lateralized cognitive ability.
• The findings underscore the importance of the right hemisphere in skilled action execution.
• Functional connectivity provides valuable insights into behavioral deficits beyond lesion location alone.