Functional connectivity between ipsilesional somatomotor network and contralesional visual network and thalamus is the strongest network predictor of hand dexterity in patients with brain tumors

Introduction: In recent years, a paradigm shift in neuroscience has been occurring from “localizationism,” or the idea that the brain is organized into separately functioning modules, toward “connectomics,” or the idea that interconnected nodes form networks as the underlying substrates of behavior and thought. Functional connectivity of brain networks can provide valuable information about neurological performance; however, connectomic correlates of motor impairments in patients with brain tumors are poorly understood. This study examines connectomic markers that may predict hand dexterity in patients with brain tumors.

Methods: Nine patients with frontal or parietal lobe brain tumors completed hand dexterity testing and resting state functional magnetic resonance imaging (rs-fMRI) prior to brain tumor resection. Hand dexterity was assessed with the 9-hole peg test and Z-score normalized by age and sex. Functional connectivity was calculated from rs-fMRI using 40 networks covering the cerebral cortex, basal ganglia, thalamus, and cerebellum and corrected for age and sex. Connectivity from the ipsilesional somatomotor network to the rest of the brain networks were entered into a stepwise linear regression to predict hand dexterity performance.

Results: The strongest predictor of hand dexterity performance was connectivity between the ipsilesional somatomotor network and the contralesional visual network (R2=0.41, p< 0.05). Adding connectivity between the somatomotor network and the contralesional thalamus increased the R2 to 0.77 (p < 0.05).

Conclusion : While often thought of as a purely motor phenomenon, dexterous hand function in patients requires connectivity of the somatomotor network with visual and thalamic networks. This suggests that facilitating recovery of hand dexterity requires reintegration of visual and thalamic input. Future studies will investigate the importance of such network reintegration into rehabilitation for recouperation of dexterous hand function.