Functional asymmetries revealed in visually guided saccades: an FMRI study

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• Eye movements are crucial for spatial exploration and attention.
• Previous research suggests right cerebral dominance for spatial attention.
• The neural basis of visually guided saccades (VGS) requires further investigation regarding hemispheric lateralization.

Purpose of the Study:

• To investigate the hemispheric functional asymmetry in brain regions involved in VGS.
• To determine if anatomical asymmetries influence the functional lateralization of VGS.
• To test the hypothesis of right cerebral dominance for the neural bases of VGS.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used in 27 right-handed participants.
• Participants performed central fixation alternating with large or small visually guided saccades (VGS).
• Analysis included hemispheric functional and anatomical asymmetry to assess VGS lateralization.

Main Results:

• Rightward asymmetrical activations were observed in saccadic/attentional networks, including lateral frontal eye fields (FEF) and anterior intraparietal sulcus (aIPS).
• Leftward asymmetrical activations were found in the saccadic motor system, specifically medial FEF and motor strip eye fields.
• Functional asymmetries were largely independent of gray matter density or sulci position differences between hemispheres.

Conclusions:

• The brain network for VGS execution exhibits specific right and left hemispheric asymmetries.
• Rightward asymmetry is linked to attentional functions, while leftward asymmetry relates to motor control, consistent with general motor cortex dominance in right-handers.
• These functional lateralizations are not explained by anatomical differences, suggesting distinct neural processing streams for attention and motor execution in VGS.