Functional asymmetries revealed in visually guided saccades: An fMRI study
Journal of Neurophysiology. 2009-11-01; 102(5): 2994-3003
DOI: 10.1152/jn.00280.2009
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1. J Neurophysiol. 2009 Nov;102(5):2994-3003. doi: 10.1152/jn.00280.2009. Epub 2009
Aug 26.
Functional asymmetries revealed in visually guided saccades: an FMRI study.
Petit L(1), Zago L, Vigneau M, Andersson F, Crivello F, Mazoyer B, Mellet E,
Tzourio-Mazoyer N.
Author information:
(1)Centre for Imaging, Neurosciences and Applications to Pathologies, UMR6232
CNRS CEA, Boulevard Henri Becquerel, BP 5229, 14074 Caen Cedex, France.
Because eye movements are a fundamental tool for spatial exploration, we
hypothesized that the neural bases of these movements in humans should be under
right cerebral dominance, as already described for spatial attention. We used
functional magnetic resonance imaging in 27 right-handed participants who
alternated central fixation with either large or small visually guided saccades
(VGS), equally performed in both directions. Hemispheric functional asymmetry was
analyzed to identify whether brain regions showing VGS activation elicited
hemispheric asymmetries. Hemispheric anatomical asymmetry was also estimated to
assess its influence on the VGS functional lateralization. Right asymmetrical
activations of a saccadic/attentional system were observed in the lateral frontal
eye fields (FEF), the anterior part of the intraparietal sulcus (aIPS), the
posterior third of the superior temporal sulcus (STS), the occipitotemporal
junction (MT/V5 area), the middle occipital gyrus, and medially along the
calcarine fissure (V1). The present rightward functional asymmetries were not
related to differences in gray matter (GM) density/sulci positions between right
and left hemispheres in the precentral, intraparietal, superior temporal, and
extrastriate regions. Only V1 asymmetries were explained for almost 20% of the
variance by a difference in the position of the right and left calcarine
fissures. Left asymmetrical activations of a saccadic motor system were observed
in the medial FEF and in the motor strip eye field along the Rolando sulcus. They
were not explained by GM asymmetries. We suggest that the leftward saccadic motor
asymmetry is part of a general dominance of the left motor cortex in
right-handers, which must include an effect of sighting dominance. Our results
demonstrate that, although bilateral by nature, the brain network involved in the
execution of VGSs, irrespective of their direction, presented specific right and
left asymmetries that were not related to anatomical differences in sulci
positions.
DOI: 10.1152/jn.00280.2009
PMID: 19710382 [Indexed for MEDLINE]