| ObjectiveNormal aging and Alzheimer's disease are associated with declines in navigational skills.The most commom manifestation were get lost in new and even familiar environment.However,the impairment of spatial navigational ability were more severe in AD than normal aging.And several spatial navigational skills showed deficit in the stage of mild cognitive impairment.The special pattern of spatial navigational impairment may help distinguish patients at higher risk of developing AD dementia.The aim of the study was to characterize the pattern of spatial navigation in different cognitive status and ages and to investigate the spatial navigational neural network.MethodsPart one:103 participants were recruited at the Memory clinic of Neurology Department in Nanjing Drum Tower Hospital.All participants underwent neuropsychological assessment and spatial navigation test in the PC version of human analog of the Morris Water Maze,which has the advantage of assessing separately allocentric and egocentric navigation.Then the performance of spatial navigation were compared in difference cognitive status(normal aging=69,mild cognitive impairment=28,mild dementia=6)and ages(<40,40?60,>60)of the participants.Part two:14 students of Nanjing university were recruited as volunteer.All participants underwent neuropsychological assessment and spatial navigation test in the PC version of human analog of the Morris Water Maze.After that all participant take a spatial navigation related task-BOLD MRI scanning.Then spatial navigation test performance and brain activation were analyzed.ResultPart one:The performance of allocentric and egocentric navigation were significantly decreased in mild dementia compared with mild cognitive impairment and normal aging(p<0.05).The performance of allocentric and egocentric navigation were also significantly decreased in mild cognitive impairment compared to normal aging(p<0.05).The participants with same cognitive level who were over 60 years old show deficits in egocentric navigation compare to the young participants(<40)(p<0.05).There was no significant differences of age in allocentric navigation,but showed a trend of impairment of allocentric navigation with aging.Part two:14 participants showed no spatial navigational disorders in PC version of human analogue Morris water maze test.Hippocampus,parahippocampus in left cerebral hemisphere and thalamus,inferior parietal lobe,posterior parietal lobe,precuneus,postcentral gyrus in bilateral cerebral hemisphere were activated in allocentric spatial navigational task(p<0.05).Caudate,putamen,pallidum,thalamus,inferior parietal lobe,posterior parietal lobe,precuneus,postcentral gyrus in bilateral cerebral hemisphere were activated in egocentric spatial navigational task(p<0.05).Bilateral angular gyrus were negative activated in allocentric and egocentric spatial navigational task(p<0.05).ConclusionPart one:The performance of spatial navigation decreased with cognitive function impairment.Allocentric and egocentric navigation impaired in mild cognitive impairment and get worse when advanced to mild dementia.The results demonstrate that navigation deficits in older age may be limited to egocentric navigation,where as allocentric navigation remain preserved.Our study clearly proved the fusibility of human analog of the Morris Water Maze to study spatial memory deficits and characterize the pattern of spatial navigation in different cognitive level and ages in Chinese population.And the results could be prepared for future study in spatial navigation.Part two:Different networks of areas subtend egocentric and allocentric strategies.Allocentric navigation seem to be processed by hippo campus and hippopotamus,whereas egocentric navigation required candidate,Putnam and Palladio.A wide network of areas with clusters in thalamus,inferior parietal lobe,posterior parietal lobe,preciousness seem involved in spatial navigational network.These areas might be responsible for encoding,exchanging and transformation of spatial information. |
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