We studied the spatial processing abilities of a 55-year-old male patient, PAO, with a right perisylvian lesion. Although the patient showed no problems in performing object recognition tasks, he was impaired in visuo-spatial tasks. PAO's most prominent deficit was a marked inability to manipulate figures mentally in the absence of an impairment in visuo-spatial working memory. His deficit would surface whenever a non-predictable rotational change in the spatial frame occurred. In contrast, his perception of spatial location and his ability to cope with size transformations were in the normal range. These results suggest that the deficit described here is selective to the rotational operation. The results are discussed in relation to the model of Kosslyn et al. (Journal of Experimental Psychology: Human Perception and Performance 1992; 18: 562-77) proposing the existence of two separate, categorical and metric, spatial coding systems, only the former of which is held to be impaired.
