Cortical control of reflexive visually-guided saccades.

Area of Science:

• Neuroscience
• Ophthalmology
• Cerebral Cortex Function

Background:

• Visually-guided saccades are crucial for visual perception and are modulated by the cerebral cortex.
• Understanding the cortical control of saccade triggering and inhibition is essential for diagnosing and treating neurological disorders affecting eye movements.

Purpose of the Study:

• To investigate the roles of the posterior parietal cortex (PPC) and prefrontal cortex (PFC) in facilitating and inhibiting reflexive visually-guided saccades.
• To determine the specific cortical areas involved in saccade control by examining patients with unilateral cerebral infarctions.

Main Methods:

• Electro-oculography was used to record saccades in 45 patients with unilateral cerebral infarctions affecting the PPC, PFC, frontal eye field (FEF), or supplementary motor area (SMA).
• Patients were divided into 8 groups based on lesion location (right/left hemisphere) and affected area.
• Saccade latency (saccade task) and error percentage (antisaccade task) were compared to 20 control subjects.

Main Results:

• Saccade latency increased significantly in the saccade task for the right PPC group and, to a lesser extent, the left PPC group.
• Latency was largely unchanged in frontal groups (PFC, FEF, SMA).
• The antisaccade task showed a significant increase in errors for both PFC groups, suggesting PFC's role in inhibiting reflexive saccades.

Conclusions:

• The superior part of the angular gyrus in the PPC is the primary area facilitating reflexive visually-guided saccades.
• The PFC is the main cortical area inhibiting reflexive visually-guided saccades.
• Hemispheric dominance, particularly of the right hemisphere, may influence saccade control.