| Background: Alzheimer’s disease(AD) is a chronic neurodegenerative disease that usually starts latently and gets worse over time. The most common symptoms are memory loss and other types of cognitive decline. Mild cognitive impairment(MCI) is considered as the prodromal stage of AD. Standardized behavioral tests and pathological studies have demonstrated that olfactory deficits exist in AD and MCI. Blood oxygen level dependent(BOLD) functional magnetic resonance imaging(f MRI) can reflect the neuron activities indirectlyand detect the in-vivo changes of olfactory functions.Objective: To investigate the value of olfactory f MRI in detecting the changes of olfactory functions in AD, MCI patients and controls(CTRL).Methods: 10 early stage AD patients, 18 MCIdue to AD patients and 21 cognitive normal CTRLs underwent a block-design olfactory f MRI scan. All the participants wereadministeredthe olfactory scale and neuropsychological test battery including Mini Mental State Examination(MMSE), Wechsler Memory Scale(WMS), Wechsler Adult Intelligence scale(WAIS-RC)、Category Fluency Test(CFT), Trail Making Test(TMT), California Verbal Learning Test II(CVLT II), Boston Naming Test,(BNT), Montreal Cognitive Assessment(Mo CA) and Clinical Dementia Rating Scale(CDR).Results:(1) The primary olfactory cortex(POC) and second olfactory cortex were well activated in CTRL group.(2) The BOLD signals with bilateral POC, hippocampus, insula andright orbitofrontal cortex(OFC) were weaker in the AD and MCI groups compared with the CTRL group, especially in the AD group. Furthermore, the BOLD signal intensity and activation volume in POC decreased significantly.Conclusion(1) Olfactory f MRI based on block-design can activate the primary and second olfactory cortex efficiently.(2) The BOLD signals were weaker in the main olfactory cortex regions and the significant decline in POC in the AD and MCI patients.Background: POC is a complex structure that is a target of incoming olfactory information from the olfactory blub, including the anterior olfactory nucleus, olfactory tubercle, piriformcortex, anterior portion of the periamygdaloidcortex and amygdala, and anterior perforated substance. The areas that evidence early neuropathyin Alzheimer’s disease, particularly in themedial temporal lobe(MTL), are areas important for memory function, and also critical for the processing of olfactoryinformation. Olfactory f MRI in the first study has confirmed the significant changing of BOLD signal in POC in AD and MCI groups compared to the CTRL group.Objective: To detect the olfactory cortex degeneration by f MRI and structural MRI, and provide a new method to setup an olfactory cortex degeneration model based on multi-modal MRI.Methods: Total structural volumes of the POC, hippocampus, andthe change of% BOLD f MRI activation were measured by manual, along with the partial correlation with olfactory scale, MMSE, Mo CA, CVLT-II, CFT, BNT,WMS-memory quotient(MQ), WAIS-(full IQ,FIQ; verbal IQ, VIQ; performance IQ,PIQ)tests in 21 CTRL, 18 MCI, and 10 AD subjects.Results:(1) Prominent atrophy in the POC, hippocampusand %BOLD f MRI activation in the POC were found in both ADand MCI subjects and showed a gradual decline from CN to MCI to AD(P<0.001).(2)The positive correlation between POC volume and %BOLD f MRI activationwas observed(P<0.05). Furthermore, both of them werepositivecorrelations with olfactory scale, hippocampus volume and MMSE, Mo CA, CVLT-II, CFT, BNT, WMS(MQ), WAIS(FIQ、VIQ、PIQ) tests(P<0.05), and significant negative correlations were found with TMT(P<0.001). %BOLD f MRI activation in POC was observed positive correlation with CFT(P<0.05),and without statistics finding in correlation between POC volume and CFT(P>0.05).Conclusion:(1) Decline in olfactory activity was correlated with the AD structural degeneration in the POC, and correlation with olfactory scale and neuropsychological test battery.(2) Olfactory cortex degeneration is a promising method in diagnosis and prediction AD in the early stage.Background: Alzheimer’s disease is considered as a typical neurodegenerative disease with gray matter(GM) atrophy. It is unclear that the pathogenesis of white matter(WM) damage in AD and the relationship with the neuropsychological test battery. Diffusion tensor imaging(DTI) is a well accepted method to detect WM changes in-vivo by the multiple DTI index of fractional anisotropy(FA), mean diffusion(MD), axial diffusivity(DA) and radial diffusivity(DR).Objective: To detect the microstructural WM damage and provide a new method of diagnosis and treatment in the early stage of AD.Methods: Voxel-based tractbased spatial-statistics(TBSS) was used to obtain whole-brain maps of main WM bundles for fractional anisotropy(FA), mean diffusivity(MD), radial diffusivity(DR) and axial diffusivity(DA)in 21 CTRL, 18 MCI, and 10 AD subjects. The differences of FA, MD, DA, and DR values were detected in CTRL vs. AD and CTRL vs. MCI groups. When considering the three groups simultaneously, meanvalues for each DTI index in the regions showing groupdifferences(i.e. controls vs. AD and controls vs. a-MCI) were used as a mask, and then FAo, MDo, DAoand DRo values were measured and compared with the neuropsychological test battery.Results:(1) FA reductions, MD, DA and DR increases were widespreadin the whole WM skeleton, and most of the FA reductions or MD increases areas overlapped the DR increases regions.(2) Relative to CTRL group, MCI patients only had some patches of FA reductions, MD, DA and DR increases surrounding the subcortical regions.(3) Significant differences were observed during the AD, MCI and CTRL groups(P<0.05).(4) FAo valueswere significant positive correlation with hippocampus volume(P<0.001). Otherwise, MDo, DAo, and DRo values were significant negative correlations with hippocampus volume(P<0.001).(5) FAo values were positive correlations with MMSE, Mo CA, CVLT-II, WMS(MQ), WAIS(FIQ、VIQ、PIQ)tests results(P<0.05). Otherwise, MDo, DAo, and DRo values were negative correlations with MMSE, Mo CA, CVLT-II, WMS(MQ),WAIS(FIQ、VIQ、PIQ)tests results(P<0.05). FAo values were negative correlations with TMT results, and MDo values inversely. But none of the DTI indexes showed correlations with BNT and CFT results(P>0.05).Conclusion:(1) White matter damage occurs in both AD and MCI patients, and with the correlation of neuropsychological tests associated with memory and executive functions. Wide spread WM damage happens in AD patients, but located in subcortical WM in MCIs. It’s a gradual progress of the WM integrity destroyed from MCI to AD stage.(2) Multiple DTI index analysis is a promising method to diagnose and predict the early stage of AD. Furthermore, FA values are more sensitive compared to MD values, and DR values are more sensitive compared to DA values. |
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