Changes in Spatial Position of Hands Modify Tactile Extinction but not Disownership of Contralesional Hand in Two Right Brain-Damaged Patients

Abstract

Somatic misperceptions and misrepresentations, like supernumerary phantom limb and denial of ownership of a given body part, have typically been reported following damage to the right side of the brain. These symptoms typically occur with personal or extrapersonal neglect and extinction of left-sided stimuli, suggesting that all these different symptoms may be linked to the same neural substrate. In the present research, we tested two right brain-damaged (RBD) patients to find out whether changing the position of the hands in space influences tactile extinction and denial of ownership to the same extent. Results showed that manipulation of the spatial position of the hands reduces tactile extinction but leaves denial of ownership of the left hand unaffected. Such a dissociation suggests that delusional misperceptions may be independent from somatic neglect and that representation of hands in space and attribution of ownership are dynamically mapped in at least partly separate neural substrates.

Acknowledgements

This research was supported by grants from FIRB (2001) and MIUR (2003), Italy to S.M.A. Thanks are due to Dr. Chiara Guerrini for her help in reconstructing the lesions, and Mr. Marco Veronese for preparing the figures.