Resting-state functional connectivity and its association with multiple domains of upper-extremity function in chronic stroke

Background. Recent work has shown that resting-state functional connectivity (rsFC) between homotopic, motor-related brain regions is associated with upper-extremity control early after stroke.

Objectives. This study examined various patterns of rsFC in chronic stroke, a time at which extensive neural reorganization has occurred. Associations between homotopic somatomotor connectivity and clinical measures, representing separate domains of upper-extremity function, were determined.

Methods. A total of 19 persons ≥6 months poststroke participated. Four connectivity patterns within a somatomotor network were quantified using functional magnetic resonance imaging. Upper-extremity gross muscle activation, control, and real-world use were evaluated with the Motricity Index, Action Research Arm Test, and accelerometry, respectively.

Results. Connectivity between homotopic regions was stronger than that in the contralesional and ipsilesional hemispheres. No differences in connectivity strength were noted between homotopic pairs, indicating that a specific brain structure was not driving somatomotor network connectivity. Homotopic connectivity was significantly associated with both upper-extremity control (r = 0.53; P=.02) and real-world use (r = 0.54; P=.02); however, there was no association with gross muscle activation (r = 0.23; P=.34). The combination of clinical measures accounted for 40% of the variance in rsFC (=.05).

Conclusions. The results reported here expand on previous findings, indicating that homotopic rsFC persists in chronic stroke and discriminates between varying levels of upper-extremity control and real-world use. Further work is needed to evaluate its adequacy as a biomarker of motor recovery following stroke.