Implicit functional-semantic evaluation of object symmetry and contralesional visual denial in a case of left unilateral neglect with damage of the dorsal paraventricular white matter.

It is well documented that right brain damaged patients with left unilateral neglect may show unconscious processing of contralesional stimuli. However, the anatomical correlates of this phenomenon are still not well defined. Here we report the case of a neglect patient with a circumscribed lesion of the dorsal parietal-occipital white matter showing clear implicit processing of the contralesional side of line drawings and object based neglect. The patient was able to perform correct semantic analysis of the symmetry (or asymmetry) of the drawings. Additional testing disclosed denial of the existence of the contralesional side of asymmetrical geometrical shapes with correct perception of symmetrical ones and of shapes without the left side. These findings provide direct evidence supporting a critical role of the dorsal visual system in the activation of conscious representations of visual stimuli.