| Objective: With the approach of the aging society,brain aging is becoming a more and more serious problem,which has been studied widely and deeply by a variety of scholars dedicating to different subjects.As we age,the brain experiences anatomical and functional changes and cognitive decline.Cognitive decline is one of the most important signal in the brain aging,it not only affected the quality of the elderly's life,ever greater burdens were placed on their families and the society.The hippocampus consisting of different subregionsis is one of the important brain areas involved in cognitive.In recent years,many researchers have studied the morphological changes of the hippocampus in the brain aging,deeping to the subregions.Resting state BOLD fMRI-function connection focuses on the interconnection among different brain regions,exploring the brain mechanism from the macroscopic level.Other studies have shown changes in resting state functional connectivity in the brain aging,but the changes of the hippocampus subregions are unclear.In the current study,we compare patterns of hippocampus subfields complex connectivity between the young and the elderly using rs-fMRI,trying to indicate the changes and the significance in the brain aging.Methods: Sixty young volunteers(23 M,37 F,range from 22 to 31 years,mean age: 26.2±1.9 years);and 61 older volunteers(23 M,38 F,range from 45 to 65 years,mean age: 52.6±5.9 years)were recruited in this study.Structural images were acquired using a 3.0 Tesla magnetic resonance scanner(GE),then the resting-state functional magnetic resonance image data was acquisitioned with an eight channel-phased array head coil.To minimize head motion,foam pads were used to fixed their head.Volunteers are supine in the scan bed,with instructions to stay relaxed and to keep eyes closed withoutfalling asleep druing the scan.Image preprocessing was conducted using DPARSFA within MATLAB.we choose the seed based analysis method,which is the simplest and the most widely used method currently to study the functional connection changes.For each participant,a mean signal intensity time course was extracted from SPM's Anatomy Toolbox for each of the ten seed regions(bilateral CA1,CA2,CA3,DG and SUB),to be used as a regressor in a correlation analysis delineating functional connectivity.Two sample t-tests were conducted in Statistical Parametric Mapping(SPM8).Finally,we observed the differences of functional connectivity between the elderly and young in REST(P<0.01),after alphasim correction.At last,the results after two sample T test were displayed on the Ch2 bet images,and we concerned the location of the clusters,MNI,the size of the clusters,and the activity intensity,trying to implicate the changes and the mechanism of hippocampus subregions in the brain aging.Results: All images are up to standard.1 Compared with the young group,the CA1 of the elderly demonstrated reduced functional connection with right inferior frontal gyrus,the CA1 of the elderly demonstrated enhanced functional connection mainly with right superior frontal gyrus and left middle frontal gyrus(Fig.1).2 Compared with the young group,the CA2 of the elderly demonstrated reduced functional connection with the right hippocampus and left Lentiform nucleus,the CA2 of the elderly demonstrated enhanced functional connection mainly with right Superior frontal gyrus,left middle frontal gyrus,right inferior temporal gyrus,left middle temporal gyrus(Fig.2).3 Compared with the young group,the CA3 of the elderly demonstrated reduced functional connection with the left hippocampus,the CA3 of the elderly demonstrated enhanced functional connection mainly with left middle frontal gyrus(Fig.3).4 Compared with the young group,the DG of the elderly demonstrated reduced functional connection with right inferior frontal gyrus,the DG of the elderly demonstrated enhanced functional connection mainly with left middlefrontal gyrus(Fig.4).5 Compared with the young group,the SUB of the elderly demonstrated reduced functional connection with the right inferior frontal gyrus and left parahippocampus;the Sub of the elderly demonstrated enhanced functional connection mainly with right Superior frontal gyrus(Fig.5).Conclusion:1 Compared with the young group,the elderly demonstrated reduced functional connection mainly with right inferior frontal gyrus,the elderly demonstrated enhanced functional connection maily with right superior frontal gyrus and left middle frontal gyrus.2 These findings suggest that rsFC alterations of the hippocampus subregions are relative independent characteristics in normal aging in human beings.3 These findings suggest that the reduced rsFCs may be associated with cognitive decline,while the enhanced rsFCs may be a compensation for cognitive decline. |
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