title: Amyloid-independent functional neural correlates of episodic memory in amnestic mild cognitive impairment.
abstract: OBJECTIVE
  Although amnestic mild cognitive impairment (aMCI) could have various biological characteristics, little attention has been given to the nature of episodic memory decline in aMCI with pathophysiologies other than Alzheimer's disease (AD), i.e., aMCI with low beta-amyloid (Aβ) burden. This study aimed to identify the functional neural basis of episodic memory impairment in aMCI with Aβ burden negative (aMCI-Aβ-) and to compare these results with aMCI with Aβ burden positive (aMCI-Aβ+).
  
  
  METHODS
  Individuals with aMCI (n = 498) were selected from the Alzheimer's Disease Neuroimaging Initiative database. Based on the mean florbetapir standard uptake value ratio, participants were classified as aMCI-Aβ- or aMCI-Aβ+. Correlations between memory scores and regional cerebral glucose metabolism (rCMglc) were analyzed separately for the two subgroups using a multiple regression model.
  
  
  RESULTS
  For aMCI-Aβ-, significant positive correlations between memory and rCMglc were found in the bilateral claustrum, right thalamus, left anterior cingulate cortex, left insula, and right posterior cingulate. For aMCI-Aβ+, significant positive correlations between memory and rCMglc were found in the temporoparietal areas. These correlation patterns remained unchanged when clinical severity was added as a covariate
  
  
  CONCLUSIONS
  Our findings indicate that memory impairment in aMCI-Aβ- is related to multimodal integrative processing and the attentional control system, whereas memory impairment in aMCI-Aβ+ is related to the typical brain memory systems and AD signature. These results suggest that although the two subgroups are clinically in the same category as aMCI, the memory impairment process depends on completely different functional brain regions according to their Aβ burden level.
authors.affiliation: Premedical Science, College of Medicine, Chosun University, 365 Pilmundaero, Dong-gu, Gwangju, Republic of Korea.
authors.forename: Eun Hyun
authors.initials: EH
authors.lastname: Seo
authors.affiliation: Department of Neuropsychiatry, School of Medicine, Chosun University/Chosun University Hospital, 365 Pilmundaero, Dong-gu, Gwangju, Republic of Korea. ilhan.choo@chosun.ac.kr.
authors.forename: I L Han
authors.initials: IL
authors.lastname: Choo
mesh_terms: D000368:Aged; D000647:Amnesia / Q000150:complications*; D016229:Amyloid beta-Peptides / Q000378:metabolism; D001921:Brain / Q000378:metabolism / Q000503:physiopathology*; D060825:Cognitive Dysfunction / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D061212:Memory, Episodic
chemical_list: D016229:Amyloid beta-Peptides
keywords: Amnestic mild cognitive impairment; Aβ burden; Episodic memory; Regional cerebral glucose metabolism