Spatial Navigation Impairment in Healthy Aging and Alzheimer’s Disease

Abstract

The prevailing number of studies dealing with spatial navigation in animals and also in human have been connecting it to the function of the medial-temporal lobe (MTL), hypothesized to serve as the neuronal basis for the spatial cognitive map. Changes in the MTL are characteristic for both healthy aging and Alzheimer’s disease (AD), with markedly more severe changes in AD. The level of hippocampal dysfunction therefore counts among the boundaries between healthy aging and development of AD. Furthermore, the decline in the spatial navigation abilities has been described for healthy aging and is among the diagnostics marks of early AD. While the impact of this decline on the life of elderly seems to be minor, subjects suffering AD become lost in new environments and later in the course of the disease even inside their homes. The spatial navigation is however a complex process using a number of brain regions besides MTL. The regions discussed in this review also include prefrontal cortex (PFC), whose changes in healthy aging are often considered more typical than changes in MTL, and parietal cortex documented to deteriorate from the very early stages of AD. Due to its complexity, spatial navigation is a promising cognitive ability to be investigated in the phases of development from healthy aged to AD. The aim of this review is to investigate the complexity of the spatial navigation and its neural basis in healthy aging and in AD, including several available studies concerning the boundary between these two. We will focus on the differences in the spatial navigation abilities between healthy aging and AD and on the potential of spatial navigation to differentiate between them. The current review follows up two papers on similar topic (Iachini et al., 2009; Moffat, 2009) and in contrast to them focuses just on wayfinding and navigation, its underlying neural structures and the distinction between healthy aging and Alzheimer’s disease.