Eye-movement training-induced plasticity in patients with post-stroke hemianopia

Area of Science:

• Neuroscience
• Ophthalmology
• Rehabilitation Medicine

Background:

• Hemianopia, a visual field defect, causes significant disability due to impaired visual perception.
• Patients with hemianopia often exhibit impaired saccades, which are rapid eye movements crucial for exploration.
• Saccade training may help compensate for visual deficits, but its effects on cortical control are not well understood.

Purpose of the Study:

• To investigate the effects of eye-movement training on the cortical control of saccades in patients with homonymous hemianopia using functional magnetic resonance imaging (fMRI).

Main Methods:

• Eight patients with occipital cortical lesions causing homonymous hemianopia underwent 4 weeks of visual field training.
• fMRI scans were performed at baseline, immediately after training, and at a 4-week follow-up in some patients.
• Brain activation during visually guided saccades was analyzed using statistical parametric mapping (SPM'99).

Main Results:

• Baseline fMRI showed activation in frontal and parietal eye fields (FEF, PEF) and supplementary eye field (SEF).
• Post-training, increased activation was observed in the left extrastriate cortex of the affected hemisphere.
• Follow-up revealed increased activation in the right peristriate cortex and contralateral SEF, with decreased activation in the left FEF.

Conclusions:

• Eye-movement training induces changes in brain activation within striate and extrastriate cortex, as well as in oculomotor areas in hemianopic patients.
• These findings suggest that saccade training can modulate neural pathways involved in visual processing and eye movement control.
• The observed alterations in cortical activation patterns may underlie the functional improvements seen after training, offering a potential therapeutic strategy.