Parietal injury may affect spatial cognition in at least three ways: right sided damage may cause left inattention (unilateral neglect), whereby the patient ignores or fails to attend to objects or events on the contralateral (left) side of extrapersonal space1; in a rare extension of this disorder, the patient may also experience the presence (often fluctuating) of an additional, supernumerary or phantom limb2—for example, a further arm at the midline in addition to a normal one on the right, and a paralysed, neglected, or “missing” one on the left. Finally, in the Gerstmann syndrome there may be, after left parietal damage, simultaneously, left-right disorientation, acalculia, agraphia, and problems with finger (or other body part) localisation or identification. Conversely, with amputation or loss (even congenital) of a limb in an otherwise healthy individual, a phantom limb may be experienced,3 with the vivid hallucinatory experience of the continued presence of that limb; parietal mechanisms have …