Spatial memory impairment in Alzheimer's disease is detectable even in patients with mild cognitive disorder

Objective. The aim was to investigate the pattern of spatial memory impairment in patients with Alzheimer's disease, and to rind whether or not the spatial memory is impaired in patients with Mild Cognitive Impairment. The qualitative and quantitative characters of impairment were compared. Subjects and Methods. Spatial memory was examined in 15 healthy volunteers and 42 patients, who had undergone a standard diagnostic procedure. These patients were subsequently classified according to clinical criteria and neuropsychological testing into four groups:Alzheimer's disease (AD), Subjective memory complaints (SMC), nonamnestic Mild Cognitive Impairment (naMCI) and amnestic Mild Cognitive Impairment (aMCI). The Hidden Goal Task test was used to examine spatial memory. This test compares two types of spatial memory-egocentric and allocentric. A real version of the test was performed in an experimental tent Blue Velvet Arena (BVA), while a virtual version, which is the map analogy of the real version, was carried out on a personal computer (PC). Results. There was found an impairment in both egocentric and allocentric spatial memory (p < 0.01) in patients with AD in the real as well as virtual versions of the test. Qualitatively similar, but quantitatively less profound impairment in egocentric (p < 0.01) and allocentric (p < 0.05) parts of spatial memory in both versions of the test was presented in patients with aMCI. Patients with naMCI were impaired in the transition from egocentric to allocentric virtual phase of the test (p < 0.05). Subjects with SMC were not impaired in any part of spatial memory. Conclusions. The spatial memory examination can be used as the basis for patients' classification into the following groups: AD, aMCI, naMCI a SMC. Our experiments have proved that in the case of AD and aMCI it is a continuity of the same quality impairment but with quantitatively different expression. Key words: Alzheimer's disease, amnestic Mild cognitive impairment, nonamnestic Mild cognitive impairment, subjective memory complaints, spatial memory, egocentric navigation, allocentric navigation.