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Left size distortion (hyperschematia) after right brain damage

From the Université de Lyon, Université Lyon 1, Inserm UMR-S 534, Bron, and Hospices Civils de Lyon Service de rééduction neurologique Hôpital Henry Gabrielle Saint Genis-Laval (G.R., C.M., Y.R., D.B.), Lyon, France; the Dipartimento di Psicologia, Università di Milano-Bicocca, and the IRCCS Istituto Auxologico Italiano (G.V.), Milan, Italy.

Address correspondence and reprint requests to Dr. G. Vallar, Università di Milano-Bicocca, Dipartimento di Psicologia, Piazza dell'Ateneo Nuovo 1, 20126 Milano, Italy; e-mail: giuseppe.vallar{at}unimib.it

Objective: To quantitate a size distortion involving the side of space contralateral to the lesion (contralesional) in two right-brain-damaged patients.

Methods: We studied two right-brain-damaged patients with lesions sparing the occipital lobe and a mild left neglect on target cancellation or line bisection. The lesions involved the temporoparietal region (Patient 1) and the basal ganglia and the insula (Patients 1 and 2). Patients were given drawing tasks and tasks requiring perceptual and visuomotor judgments of horizontal extent.

Results: In drawing objects such as a daisy both from memory and by copying, patients exhibited a disproportionate enlargement of the left-hand side of objects and added more left-sided petals to the drawn daisy. This pathologic behavior persisted when the patients were blindfolded and was likely to reflect a perceptual, rather than premotor, size distortion. In a task requiring the perceptual matching of two rectangles, patients underestimated the left-sided stimulus. In a visuomotor task requiring the reproduction of the horizontal extent of a segment, patients exhibited a hyperextension, when a leftward movement was required.

Conclusions: We showed a disordered representation of extrapersonal space, possibly involving a contralesional relaxation of the spatial medium. The deficit does not arise at the level of retinotopic coordinate frames and is independent of unilateral spatial neglect.

Supported in part by Miur Prin grants 2003 and 2005, a FAR Grant 2006 (Dr. Vallar), and an SNLF Grant (Dr. Michel).

Disclosure: The authors report no conflicts of interest.

Presented in part to the Joint Meeting of the Société de Neuropsychologie de Langue Française and the Società Italiana di Neuropsicologia (Paris, October 17–18, 2002).

Received December 29, 2005. Accepted in final form July 28, 2006.

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