Abstract and Keywords
While reviewing Bálint’s syndrome and its different interpretations, a new framework of the anatomical-functional organization of the posterior parietal cortex (dorsal visual stream) is proposed in this chapter based on recent psychophysical, neuropsychological, and neuroimaging data. In particular, the authors identify two main aspects that exclude eye and hand movement disorders as specific deficit categories (optic ataxia). The first aspect is spatial attention, and the second is visual synthesis. Ipsilesional attentional bias (and contralesional extinction) may be caused by the dysfunction of the saliency map of the superior parietal lobule (SPL) directly (by its lesion) or indirectly (by a unilateral lesion creating an inter-hemispheric imbalance between the two SPL). Simultanagnosia may appear as concentric shrinking of spatial attention due to bilateral SPL damage. Other symptoms such as spatial disorganization (constructional apraxia) and impaired spatial working memory or visual remapping may be attributable to the second, nonlateralized aspect. Even if described initially in patients with left-sided neglect, these deficits occur in the entire space and only after right inferior parietal lobule (IPL) damage. These two aspects might also correspond to the ventral and dorsal networks of exogenous and endogenous attention, respectively.
Keywords: Bálint’s syndrome, extinction, simultanagnosia, neglect, optic ataxia, constructional apraxia, endogenous/exogenous attention, visual remapping, saliency maps, dorsal/ventral network of attention, dorsal/ventral visual streams
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