title: Path Complexity in Virtual Water Maze Navigation: Differential Associations with Age, Sex, and Regional Brain Volume.
abstract: Studies of human navigation in virtual maze environments have consistently linked advanced age with greater distance traveled between the start and the goal and longer duration of the search. Observations of search path geometry suggest that routes taken by older adults may be unnecessarily complex and that excessive path complexity may be an indicator of cognitive difficulties experienced by older navigators. In a sample of healthy adults, we quantify search path complexity in a virtual Morris water maze with a novel method based on fractal dimensionality. In a two-level hierarchical linear model, we estimated improvement in navigation performance across trials by a decline in route length, shortening of search time, and reduction in fractal dimensionality of the path. While replicating commonly reported age and sex differences in time and distance indices, a reduction in fractal dimension of the path accounted for improvement across trials, independent of age or sex. The volumes of brain regions associated with the establishment of cognitive maps (parahippocampal gyrus and hippocampus) were related to path dimensionality, but not to the total distance and time. Thus, fractal dimensionality of a navigational path may present a useful complementary method of quantifying performance in navigation.
authors.affiliation: Institute of Gerontology and Psychology Department, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Daugherty
authors.affiliation: Institute of Gerontology and Psychology Department, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Yuan
authors.affiliation: Institute of Gerontology and Psychology Department, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Dahle
authors.affiliation: Institute of Gerontology and Psychology Department, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Bender
authors.affiliation: Institute of Gerontology and Psychology Department, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Yiqin
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Institute of Gerontology and Psychology Department, Wayne State University, Detroit, MI 48202, USA.
authors.forename: Naftali
authors.initials: N
authors.lastname: Raz
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D018782:Maze Learning / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D009949:Orientation; D012737:Sex Factors; D065854:Spatial Navigation / Q000502:physiology*; D013997:Time Factors; D014584:User-Computer Interface; D055815:Young Adult
keywords: age; brain; fractal dimensionality; hippocampus; spatial navigation