Cognitive reserve modifies the relationship between neural function, neural injury and upper-limb recovery after stroke

Objective: To investigate whether cognitive reserve modifies the relationship between functional connectivity, lesion volume, stroke severity and upper-limb motor impairment and recovery in stroke survivors. Methods: Ten patients with first-ever ischemic middle cerebral artery stroke completed the Cognitive Reserve Index Questionnaire at baseline. Upper-limb motor impairment and functional connectivity were assessed using the Fugl-Meyer Assessment and electroencephalography respectively at baseline and 3-months post-stroke. A debiased weighted phase lag index was computed to estimate functional connectivity between electrodes. Partial least squares (PLS) regression identified a connectivity model that maximally predicted variance in the degree of upper-limb impairment. Regression models were generated to determine whether cognitive reserve modified the relationship between neural function (functional connectivity), neural injury (lesion volume), stroke severity (National Institutes of Health Stroke Scale) and upper-limb motor impairment at baseline and recovery at 3-months (Fugl-Meyer Assessment). Results: The addition of cognitive reserve to a regression model with a dependent variable of upper-limb motor recovery and independent variables of functional connectivity between the ipsilesional motor cortex and parietal cortex, stroke severity and lesion volume improved model efficiency (∆BIC=-7.07) despite not reaching statistical significance (R²=0.90, p=0.07). Cognitive reserve did not appear to improve regression models examining motor impairment at baseline. Conclusions: Preliminary observations suggest cognitive reserve might modify the relationship between neural function, neural injury, stroke severity and upper-limb motor recovery. Further investigation of cognitive reserve in motor recovery post-stroke appears warranted.