SPATIAL DISORIENTATION IN SENILE DEMENTIA OF THE ALZHEIMER-TYPE

Memory deficiencies and spatial disorientation are among the earliest and most readily observed manifestations of senile dementia of the Alzheimer type (DAT). Although the incapacitating impact of disorientation is well recognized, it has received relatively little attention in the neuropsychological literature. This paper reviews the principal works done on orientation problems in DAT. In the first part, it is noted that the concept has traditionally been viewed within the framework of spatial representation and cognitive maps. During the seventies, this view was progressively replaced by a new conceptualization which emphasized the spatio-cognitive and decision making processes necessary for purposeful mobility. Also, the review outlines some conceptual dimensions affecting research such as the distinction between locomotor-space and represented space, familiar and new environments and micro- and macro-spaces. In the second part, having introduced the concept of spatial orientation, the review follows the work done on spatial orientation deficits in patients with brain lesions, a related field which has been more extensively looked at in patients with DAT. Based on this review, various explanatory hypotheses of disorientation in DAT are discussed. Memory impairments, although affecting spatial orientation, can not by themselves account for disorientation in DAT. Experimental work has shown that the ability to solve spatial and orientation tasks in which the role of memory is minimal also tends to be affected. The same observation applies to other explanatory hypotheses based on perceptual and visuo-spatial exploration. Finally, the disorientation in DAT is discussed in light of the conceptual dimensions referred to earlier.