Pathway-dependent brain stimulation responses indicate motion processing integrity after stroke

Area of Science:

• Neuroscience
• Neurorehabilitation
• Visual Neuroscience

Background:

• Homonymous hemianopia (HH) is a common visual impairment after stroke, impacting survivors' quality of life.
• Existing treatments focus on perceptual training to enhance residual visual pathways.
• Understanding plasticity mechanisms in the visual cortex is crucial for developing effective interventions.

Purpose of the Study:

• To investigate the efficacy of cortico-cortical paired associative stimulation (ccPAS) in inducing plasticity within the V1-MT pathway.
• To assess the impact of bidirectional ccPAS on visual motion discrimination in stroke patients with HH.
• To explore electrophysiological and structural correlates of ccPAS response.

Main Methods:

• A double-blind, crossover study involving 16 stroke patients with HH.
• Application of bidirectional ccPAS (V1-to-MT and MT-to-V1) targeting the motion processing pathway.
• Assessment of motion discrimination, EEG-Granger Causality, and structural integrity (V1-MT).

Main Results:

• MT-to-V1 ccPAS significantly enhanced motion direction discrimination in the blind field.
• Electrophysiological evidence of increased top-down MT-to-V1 input was observed only in patients who improved.
• Responders showed enhanced functional coupling within the visual network and preserved V1-MT structural integrity.

Conclusions:

• Targeted ccPAS can effectively modulate residual visual pathways in stroke patients.
• The findings suggest ccPAS as a potential therapeutic tool for visual recovery in HH.
• Patient stratification based on functional and structural markers may optimize ccPAS efficacy.