Brain reorganization: altered functional connectivity in reward network after stroke

Motivation is key to functional recovery after stroke and is partly driven by reward pathway activation. Impaired reward-related striatal activation during motor learning may hinder rehabilitation that relies on motivational feedback. Even without direct damage to reward areas, stroke may disrupt reward network connectivity. What drives this reward processing network alterations is not known. This study examines how stroke alters reward-related functional connectivity during motor learning with monetary reward.

Subacute stroke patients (n = 28) and age-matched healthy controls (n = 18) performed an arc-pointing motor learning task with the wrist and received performance-dependent monetary rewards during functional magnetic resonance imaging (fMRI). A generalized psychophysiological interactions model (gPPI) was used to evaluate differences in reward network functional connectivity.

In the reward interval, stroke patients exhibited significant functional connectivity changes within the reward network compared to healthy controls. Increased connectivity was observed between the ventral tegmental area, substantia nigra, striatum, precentral gyrus and orbitofrontal cortex, whereas decreased connectivity was found between ventral tegmental area and nucleus accumbens. Of note, motor performance and monetary reward did not differ between groups.

Stroke leads to significant reward network reorganization, with both hyper- and hypoconnectivity in cortical and subcortical regions. Increased connectivity may reflect compensation; decreased connectivity may impair reward processing and learning. These findings support targeting reward pathways-e.g., via feedback or brain stimulation-to boost motor recovery.