Project D1 – The effect of aging on basic aspects of spatial orientation and navigation
Spatial navigation and orientation are crucial for everyday functioning in a complex environment. Elderly, non-demented individuals report self-perceived deficits in navigation, and several studies have documented degradation. Navigation and spatial memory are dependent on vestibular input: bilateral vestibular loss in humans causes hippocampal atrophy, which correlates with navigational deficits in a virtual water maze [1]. Consequently, possible reasons for age-related deficits could be age-dependent degeneration of vestibular hair cells and pathways [2] or hippocampal degeneration occurring with cerebral or vestibular aging. However, navigation is based on a number of separate and distinct processes including spatial memory, place learning, and path integration. Complex path integration tasks pose problems even to young, healthy subjects [3]. Performing a simultaneous, dual task causes large systematic errors in very simple navigation based on path-integration [4]. Since hippocampal volume appears to correlate with navigation performance only in the young but not the elderly [5], why performance deteriorates remains an open question. As most studies in elderly did not distinguish between navigational processes (for an exception, see [6]), we intend to carry out a systematic investigation of vestibular function and navigational abilities in elderly.
Objectives and description of work
In the present project, we will concentrate on the effects of vestibular and hippocampal aging on path integration using paradigms such as locomotor pointing or passive transport in real and virtual environments (Bernstein VR Facility). Special emphasis will be given to the role of concurrent mental tasks, which interfere with path integration [4] and are known to pose severe problems to the elderly. We will use virtual navigation tasks together with quantitative vestibular tests, functional magnetic resonance imaging (fMRI), and brain volumetry to clarify differences in brain activation between age groups [TB]. Neuropsychological test batteries will control for general effects of aging on cognition. Mathematical modelling of path integration (at the systems level, using neural networks) will be used to investigate possible mechanisms affected by aging, such as increased sensory uncertainty, substitution for increasing vestibular loss, changes in strategy, or effects on temporal processing [SG].
[1]: Brandt et al. Brain 2005. [2] Jahn et al. Brain 2003. [3] Glasauer & Brandt J Neurophysiol 2007. [4]: Glasauer et al. J Neurophysiol 2007. [5]: Moffat et al. Cereb Cortex 2007. [6] Allen et al. Percept Psychophys 2004.
