Decreased functional magnetic resonance imaging activity in the hippocampus in favor of the caudate nucleus in older adults tested in a virtual navigation task
Hippocampus. 2013-10-25; 23(11): 1005-1014
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1. Hippocampus. 2013 Nov;23(11):1005-14. doi: 10.1002/hipo.22181.
Decreased functional magnetic resonance imaging activity in the hippocampus in
favor of the caudate nucleus in older adults tested in a virtual navigation task.
Konishi K(1), Etchamendy N, Roy S, Marighetto A, Rajah N, Bohbot VD.
(1)Douglas Mental Health University Institute, Department of Psychiatry, McGill
University, Verdun, Quebec, Canada.
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.
Copyright © 2013 Wiley Periodicals, Inc.
PMID: 23929534 [Indexed for MEDLINE]