Disorientation in Alzheimer disease: Allocentric and egocentric mechanisms
Introduction. Spatial disorientation is a common symptom of Alzheimer Disease (AD). The cognitive mechanisms of this difficulty have not been explored in this population. It is unclear which commonly used standard measures of neuropsychological function are more predictive of the risk of getting lost or disoriented. Ability to use allocentric and egocentric reference frames in AD has received little attention in research. We hypothesized that patients with AD will be more impaired on tasks of allocentric function than egocentric function and that this impairment will be more pronounced in AD sample compared to the healthy age-matched controls. Relative contributions of allocentric and egocentric functions to reports of orientation and wayfinding ability were explored. Method. Thirty-five participants (22 controls, 13 AD) were assessed with computer-based Allocentric-Egocentric Test, standardized measures of attention and executive function, and a self-report (controls) or caregiver-report (AD group) measure of daily wayfinding ability. Results. Participants with AD performed significantly worse than age-matched controls on all spatial tasks. Once the effects of interference that confounded performance on the Egocentric-I condition were controlled for (Egocentric-NI condition), participants with AD were more affected on the allocentric than the egocentric task. Participants with AD performed significantly worse on the allocentric task than age-matched controls, but performance on the egocentric task (Egocentric-NI) was not significantly different between the groups. Neuropsychological data revealed that attention and executive function together were highly predictive of all tests of spatial function regardless of frame of reference. However, only attention alone contributed significantly to the models on both egocentric tasks, and not on allocentric task. Executive function alone did not contribute significantly to any of the models. Performance on the allocentric and the two types of egocentric tasks together was highly predictive of reports of daily wayfinding ability, but none of these alone contributed significantly to the model. Conclusions . Allocentric functioning is differentially affected by the AD process compared to the egocentric functioning. Attention, but not executive function, is an important cognitive mechanism of egocentric, but not allocentric orientation. In our sample, ability to use either frame of reference alone did not explain daily wayfinding ability.
0633: Cognitive psychology