Letters lost in space: hemispace dependent handwriting errors.

Although handwriting is a daily life activity commonly attributed to the left hemisphere in the majority of right-handers, it is also known to require attentional and spatial mechanisms that rely on right hemispheric processing. The underlying spatial organization of handwriting in patients with right brain damage remains unresolved. Here we show in a patient with circumscribed right superior parietal damage that handwriting systematically depends on the hand's position in space with respect to her body-midline. Most importantly, handwriting in contralesional space not only leads to spatial but also to language errors. This suggests that the right hemisphere's role in handwriting may surpass its generally assumed purely spatial contribution. We discuss our results in term of co-registration between both cerebral hemispheres in language processing.