Evidence for separate allocentric and egocentric space processing in neglect patients

Spatial orientation was investigated in two different conditions: (a) when the shape of the enclosure was the only available information; (b) when a c learly perceivable visual cue was added. Three groups of subjects were inve stigated: normal controls, right brain-damaged patients without and with he mispatial neglect. The performance of the first two groups clearly demonstr ated the capacity to use the geometric properties of the environment and to integrate this information with an additional visual cue. Considered as a group, patients with hemispatial neglect were able to use the shape of the environment and, to a lesser extent, the additional visual cue. However, in dividual differences suggest two opposite performance patterns: two patient s responded randomly when the shape of the environment was the only availab le information, and they improved considerably when the cue was offered; tw o other patients showed normal competence in dealing with the geometrical p roperties of the environment, but were unable to take advantage of the cue. The different lesion site in these two types of patients suggests a possibl e dissociation of processing based upon allocentric or egocentric coding of space in humans as well as in animals.