Patients with AD often become disoriented and get lost, even in familiar environments. This is frightening and frustrating to them and worrisome for loved ones and caregivers. A recent study, conducted by scientists at the University of Rochester Medical Center, may provide an explanation for this phenomenon.
When people move through a space, they see the environment around them change. It appears to be flowing past them. This changing picture is called "optic flow." People can orient themselves and know what direction they are moving in because of the brain's ability to process optic flow information.
In this study, investigators tested three groups of people–11 with probable AD, 12 healthy older people, and 6 healthy younger individuals–to see whether difficulties in perceiving patterns of optic flow were a factor in the spatial disorientation experienced by AD patients (Tetewsky and Duffy, 1999). The participants were asked to take several tests designed to judge their ability to analyze optic flow and master spatial navigation. One set of tests involved watching computer-generated moving patterns of dots of light on a screen. In another test, the research team escorted each person on a complex route through a hospital and then asked questions about the path, layout, direction of turns, and landmarks. Compared to the healthy study participants, the AD patients performed more poorly on both the optic flow tests and the spatial navigation test. This suggests that the disease interferes with a person's ability to use visual information to guide self-movement and, thus, may be a reason why AD patients often become lost.
Source: National Institutes of Health; National Institute on Aging
1999 PROGRESS REPORT ON ALZHEIMER'S DISEASE