The assessment of patients suffering from unilateral spatial neglect, a common neuropsychological syndrome caused by a neurological damage of the right cerebral hemisphere and characterized by difficulties in exploring the left visual field or by a loss of awareness of stimuli occurring in this field, has allowed important advances in our understanding of the neural networks involved in the orientation of visuo-spatial attention. However, the precise contribution of structures shaping the medial face of the brain to this function vital for visually-guided behaviors was to date not clearly established, mainly because available studies were mostly based on vascular injuries as lesion model – a common neurological condition that affects the medial structures very occasionally.
In this study conducted by two researchers from the Institute of Functional Genomics (CNRS/INSERM/Université de Montpellier), Guillaume Herbet and Hugues Duffau, and recently published in the journal Nature Communications, it is shown that two cerebral areas lodged in the medial part of the frontal cortex, the supplementary and the cingular eye fields, as well as their underlying white matter connectivity, contribute to the voluntary deployment of visuo-spatial attention, as damage to these structures causes a specific form of spatial neglect (visuo-motor exploratory neglect) characterized by a deficit in exploring the left visual field without loss of consciousness of it.
To achieve this finding, the researchers relied on the longitudinal (i.e. before and after surgery) behavioral assessment of a large sample of patients harboring a low-grade glioma, a rare tumor of the central nervous system that frequently affects the medial frontal cortex. Anatomo-functional correlations were performed by combining machine learning-based lesion-deficit mapping and structural disconnection analyses. The obtained results showed that surgical removal of the medial eye fields disturbed the voluntary exploration of the left visual scene during a visual search paradigm after surgery, as well as damage to the branch I of the superior longitudinal fasciculus – an associative white matter tract interconnecting the medial part of the frontal and parietal cortex. These results have important implications for current neurocognitive and neuro-computational models of visuo-spatial attention.
Spatial mapping of the statistical relationship between the location of surgical resections and visuo-motor exploratory neglect.
