Age-related impairment of navigation and strategy in virtual star maze.

BACKGROUND: Although it is well known that aging impairs navigation performance, the underlying mechanisms remain largely unknown. Egocentric strategy requires navigators to remember a series of body-turns without relying on the relationship between environmental cues. Previous study suggested that the egocentric strategy, compared with non-egocentric strategy, was relatively unimpaired during aging. In this study, we aimed to examine strategy use during virtual navigation task and the underlying cognitive supporting mechanisms in older adults. METHODS: Thirty young adults and thirty-one older adults were recruited from the local community. This study adapted star maze paradigm using non-immersive virtual environment. Participants moved freely in a star maze with adequate landmarks, and were requested to find a fixed destination. After 9 learning trials, participants were probed in the same virtual star maze but with no salient landmarks. Participants were classified as egocentric or non-egocentric strategy group according to their response in the probe trial. RESULTS: The results revealed that older adults adopting egocentric strategy completed the navigation task as accurate as young adults, whereas older adults using non-egocentric strategy completed the navigation task with more detours and lower accuracy. The relatively well-maintained egocentric strategy in older adults was related to better visuo-spatial ability. CONCLUSIONS: Visuo-spatial ability might play an important role in navigation accuracy and navigation strategy of older adults. This study demonstrated the potential value of the virtual star maze in evaluating navigation strategy and visuo-spatial ability in older adults.

Putting age-related task activation into large-scale brain networks: A meta-analysis of 114 fMRI studies on healthy aging.

Normal aging is associated with cognitive decline and underlying brain dysfunction. Previous studies concentrated less on brain network changes at a systems level. Our goal was to examine these age-related changes of fMRI-derived activation with a common network parcellation of the human brain function, offering a systems-neuroscience perspective of healthy aging. We conducted a series of meta-analyses on a total of 114 studies that included 2035 older adults and 1845 young adults. Voxels showing significant age-related changes in activation were then overlaid onto seven commonly referenced neuronal networks. Older adults present moderate cognitive decline in behavioral performance during fMRI scanning, and hypo-activate the visual network and hyper-activate both the frontoparietal control and default mode networks. The degree of increased activation in frontoparietal network was associated with behavioral performance in older adults. Age-related changes in activation present different network patterns across cognitive domains. The systems neuroscience approach used here may be useful for elucidating the underlying network mechanisms of various brain plasticity processes during healthy aging.

Toward systems neuroscience in mild cognitive impairment and Alzheimer's disease: a meta-analysis of 75 fMRI studies.

Most of the previous task functional magnetic resonance imaging (fMRI) studies found abnormalities in distributed brain regions in mild cognitive impairment (MCI) and Alzheimer's disease (AD), and few studies investigated the brain network dysfunction from the system level. In this meta-analysis, we aimed to examine brain network dysfunction in MCI and AD. We systematically searched task-based fMRI studies in MCI and AD published between January 1990 and January 2014. Activation likelihood estimation meta-analyses were conducted to compare the significant group differences in brain activation, the significant voxels were overlaid onto seven referenced neuronal cortical networks derived from the resting-state fMRI data of 1,000 healthy participants. Thirty-nine task-based fMRI studies (697 MCI patients and 628 healthy controls) were included in MCI-related meta-analysis while 36 task-based fMRI studies (421 AD patients and 512 healthy controls) were included in AD-related meta-analysis. The meta-analytic results revealed that MCI and AD showed abnormal regional brain activation as well as large-scale brain networks. MCI patients showed hypoactivation in default, frontoparietal, and visual networks relative to healthy controls, whereas AD-related hypoactivation mainly located in visual, default, and ventral attention networks relative to healthy controls. Both MCI-related and AD-related hyperactivation fell in frontoparietal, ventral attention, default, and somatomotor networks relative to healthy controls. MCI and AD presented different pathological while shared similar compensatory large-scale networks in fulfilling the cognitive tasks. These system-level findings are helpful to link the fundamental declines of cognitive tasks to brain networks in MCI and AD.

[Study on visual evoked related potentials in young adults of different COMT genotypes by using a numeric working memory task].

AIM: To explore the change of number working memory ability in healthy young adults, a continuous 3-back number working memory task were performed for an hour and 12 Blocks according to different COMT genotypes of young adults. METHODS: 18 different genotype subjects were chosen from 112 healthy young adults, P3 event-related potentials was utilized to observe the relationship between this COMT polymorphism and cortical physiology in a continuous working memory task. RESULTS: Subjects bearing the Val/Val homozygote had significantly higher mean P3 amplitudes than Val/Met heterozygote (P < 0.01), however, no significant differences in comparison to Met/Met homozygote. CONCLUSION: Val/Met Heterozygote subjects are associated with the poorest performance of working memory. There is a relationship between COMT genotype and P3 visual event-related potentials evoked from 3-back task.