Saccade induced cortical activation in patients with post-stroke visual field defects

Area of Science:

• Neuroscience
• Ophthalmology
• Neurology

Background:

• Hemianopia, resulting from visual field loss, causes significant disability.
• Patients with hemianopia often exhibit impaired saccadic eye movements.
• Saccade training may improve visual search strategies in affected individuals.

Purpose of the Study:

• To investigate the neural representation of saccades in patients with post-stroke hemianopia using functional Magnetic Resonance Imaging (fMRI).
• To compare brain activation patterns during visually guided saccades between patients with hemianopia and healthy controls.

Main Methods:

• Functional MRI (fMRI) was employed to measure brain activation during visually guided saccades.
• Ten patients with pure occipital cortical lesions causing homonymous hemianopia and ten healthy controls participated.
• Statistical Parametric Mapping (SPM'99) was used to analyze differences in brain activation.

Main Results:

• Healthy subjects showed significant activation in bilateral frontal and parietal eye fields and the supplementary eye field.
• These areas were also activated in hemianopia patients, but to a lesser extent.
• Patients exhibited increased activation in the posterior parietal cortex of the unaffected left hemisphere.

Conclusions:

• Post-stroke hemianopia is associated with alterations in the frontoparietal network controlling saccades.
• These findings suggest that visual field defects impact the cortical control of eye movements.
• The posterior parietal cortex may play a compensatory role in hemianopia.