Reaching movements may reveal the distorted topography of spatial representations after neglect.
Jackson SR., Newport R., Husain M., Harvey M., Hindle JV.
It has been proposed that patients with spatial neglect fail to respond appropriately toward stimuli opposite their brain lesion because they have an impairment of directing attention. However, a disorder of 'intention' - or movement initiation - has also been demonstrated in this condition. Recently, the paths of neglect patients' reaches have been shown to be abnormally curved, but it is unclear whether this impairment is visual or motor. Here, we show for the first time that reaches to and from identical positions executed by three patients recovering from neglect are significantly more curved to visually defined targets compared to when the same targets are defined proprioceptively. These findings indicate that abnormal hand paths in neglect result from an impairment in the visual representation of space used to guide reaches but without any general failure of spatial representation of target position. Furthermore, the curved hand paths reveal how the topography of that representation is distorted in spatial neglect.