Brain reorganization: altered functional connectivity in reward network after stroke

Area of Science:

• Neuroscience
• Neurorehabilitation
• Functional Neuroimaging

Background:

• Motivation is crucial for post-stroke recovery, often linked to reward pathway activation.
• Stroke can disrupt striatal activation and reward network connectivity, potentially hindering motor learning and rehabilitation.
• The underlying mechanisms of these reward processing alterations post-stroke remain unclear.

Purpose of the Study:

• To investigate how stroke affects functional connectivity within the brain's reward network during motor learning.
• To examine the relationship between stroke, reward processing, and motor task performance.

Main Methods:

• Utilized functional magnetic resonance imaging (fMRI) to study subacute stroke patients (n=28) and healthy controls (n=18).
• Employed a generalized psychophysiological interactions (gPPI) model to analyze reward network functional connectivity during a wrist motor learning task with monetary rewards.
• Compared functional connectivity patterns between stroke patients and controls.

Main Results:

• Stroke patients showed significant alterations in reward network functional connectivity compared to controls.
• Observed increased connectivity between ventral tegmental area, substantia nigra, striatum, precentral gyrus, and orbitofrontal cortex.
• Found decreased connectivity between ventral tegmental area and nucleus accumbens, despite similar motor performance and reward receipt between groups.

Conclusions:

• Stroke induces substantial reorganization of the reward network, characterized by both increased (hyperconnectivity) and decreased (hypoconnectivity) connections.
• Hyperconnectivity might represent compensatory mechanisms, while hypoconnectivity could impair reward processing and learning.
• Findings suggest that interventions targeting reward pathways, such as feedback or brain stimulation, could enhance motor recovery after stroke.