Effects of aging and dementia upon recent visuospatial memory

Abstract

In two experiments, a total of 20 young normals, 29 elderly normals, and 76 elderly demented subjects were administered a computerized delayed visuospatial recall task. Subjects were instructed to remember which room of a 25-room house had a light on in the window. A choice reaction time task was interposed during the delay interval (0–120 seconds) between stimulus presentation and recall. The test was designed to be (1) face valid-relevant to the subjects' everyday lives, (2) sensitive and specific to the cognitive decline associated with senile dementia of the Alzheimer's type (SDAT), and (3) comparable to animal memory tests. Immediate recall of the spatial location of a single stimulus was found to be deficient in severely demented subjects only, and all groups exhibited a decline in recall accuracy with increasing delay intervals. This decline in recall accuracy was greatest in severely demented subjects, smaller in less demented subjects, still smaller in aged normals, and smallest in young normals. No significant forgetting of spatial location occurred between 30 and 120 seconds after stimulus presentation. Increasing stimulus number decreased recall accuracy in all groups and the elderly and elderly demented subjects were more sensitive to the increase in stimulus load than the young normals. Choice reaction time also proved sensitive to age and severity of dementia. Correlation analyses demonstrated that delayed spatial recall (as well as choice reaction time) is highly correltated with clinically evaluated global cognitive status, as well as with tests of verbal recall. These results confirm previous reports that spatial recall is impaired by both age and SDAT. It is concluded that this test procedure and others applying similar approaches should be useful in the assessment of age-related cognitive dysfunction and in the evaluation of potential pharmacological treatments for these disorders.