Decreased functional magnetic resonance imaging activity in the hippocampus in favor of the caudate nucleus in older adults tested in a virtual navigation task.
The neuroimaging literature has shown consistent decreases in functional magnetic resonance imaging (fMRI) activity in the hippocampus of healthy older adults engaged in a navigation task. However, navigation in a virtual maze relies on spatial or response strategies known to depend on the hippocampus and caudate nucleus, respectively. Therefore, since the proportion of people using spatial strategies decreases with normal aging, we hypothesized that it was responsible for the observed decreases in fMRI activity in the hippocampus reported in the literature. The aim of this study was to examine the effects of aging on the hippocampus and caudate nucleus during navigation while taking into account individual navigational strategies. Young (N = 23) and older adults (N = 29) were tested using fMRI on the Concurrent Spatial Discrimination Learning Task, a radial task that dissociates between spatial and response strategies (in Stage 2) after participants reached criteria (in Stage 1). Success on Stage 2 requires that participants have encoded the spatial relationship between the target object and environmental landmarks, that is, the spatial strategy. While older adults required more trials, all participants reached criterion. fMRI results showed that, as a group, young adults had significant activity in the hippocampus as opposed to older adults who instead had significant activity in the caudate nucleus. Importantly, individual differences showed that the older participants who used a spatial strategy to solve the task had significant activity in the hippocampus. These findings suggest that the aging process involves a shift from using the hippocampus toward the caudate nucleus during navigation but that activity in the hippocampus is sustained in a subset of healthy older adults engaged in spatial strategies.
Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Verdun, Quebec, Canada.
Kyoko
K
Konishi
Nicole
N
Etchamendy
Shumita
S
Roy
Aline
A
Marighetto
Natasha
N
Rajah
Véronique D
VD
Bohbot
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002421:Caudate Nucleus / Q000502:physiology*; D004193:Discrimination Learning / Q000502:physiology; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D018782:Maze Learning / Q000502:physiology; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D013028:Space Perception / Q000502:physiology; D049490:Systems Biology; D014584:User-Computer Interface; D055815:Young Adult
aging; radial maze; response learning; spatial memory; striatum