3D left hyperschematia after right brain damage

Abstract

A quantitative assessment of a distortion involving the left side of space, both in two-dimensional (drawing), and three-dimensional (modeling), visuo-constructional tasks is reported in a patient with a right temporoparieto-occipital lesion, and left hemianopia, without visuospatial neglect. In drawing and clay modeling of objects the patient exhibited a disproportionate enlargement of the left-hand side of objects. Matching perceptually two rectangles, the patient underestimated the left side of the stimulus. In a visuomotor task requiring the reproduction of horizontal extent, the patient exhibited a leftward overextension. Observations in two right-brain-damaged patients by Rode, Michel, Rossetti, Boisson, and Vallar (2006, Neurology, 67, 1801) are confirmed and extended. The patient's impairment may involve a disordered representation of extrapersonal space, with a leftward disproportionate expansion of the spatial medium (‘hyperschematia’). Accordingly, symmetrical productions are compensatorily expanded leftwards, and the left sides of objects are perceived as smaller in horizontal extent. The disorder is largely independent of left spatial neglect.

Keywords:

• Hyperschematia
• Size distortion
• Left spatial neglect
• Left hemianopia
• Right brain damage

We are grateful to Mr Jean-Louis Borach for technical support. Parts of this study were presented to the euroNpsy Meeting 2006 (Toulouse, October 18–20, 2006). This study has been supported in part by a MUR PRIN 2005 Grant to G.V.