title: Role of hippocampal CA1 atrophy in memory encoding deficits in amnestic Mild Cognitive Impairment.
abstract: Identifying the specific substrates of memory deficits in early Alzheimer's disease would help to develop clinically-relevant therapies. The present study assesses the relationships between encoding versus retrieval deficits in patients with amnestic Mild Cognitive Impairment (aMCI) and atrophy specifically within the hippocampus and throughout the white matter. Twenty-two aMCI patients underwent T1-weighted MRI scans and neuropsychological testing. Grey matter and white matter segments obtained from the MRI images were each entered in correlation analyses, assessed only in the hippocampus for grey matter segments, with encoding and retrieval memory performances. For the grey matter segments, the resulting spmT correlation maps were then superimposed onto a 3D surface view of the hippocampus to identify the relative involvement of the different subfields, a method already used and validated elsewhere. Memory encoding deficits specifically correlated with CA1 subfield atrophy, while no relationship was found with white matter atrophy. In contrast, retrieval deficits were weakly related to hippocampal atrophy and did not involve a particular subfield, while they strongly correlated with loss of white matter, specifically in medial parietal and frontal areas. In aMCI patients, encoding impairment appears specifically related to atrophy of the CA1 hippocampal subfield, consistent with the predominance of encoding deficits and CA1 atrophy in aMCI. In contrast, episodic retrieval deficits seem to be underlain by more distributed tissue losses, consistent with a disruption of a hippocampo-parieto-frontal network.
authors: INSERM, U1077 Caen, France.
authors: Marine
authors: M
authors: Fouquet
authors: Béatrice
authors: B
authors: Desgranges
authors: Renaud
authors: R
authors: La Joie
authors: Denis
authors: D
authors: Rivière
authors: Jean-François
authors: JF
authors: Mangin
authors: Brigitte
authors: B
authors: Landeau
authors: Florence
authors: F
authors: Mézenge
authors: Alice
authors: A
authors: Pélerin
authors: Vincent
authors: V
authors: de La Sayette
authors: Fausto
authors: F
authors: Viader
authors: Jean-Claude
authors: JC
authors: Baron
authors: Francis
authors: F
authors: Eustache
authors: Gaël
authors: G
authors: Chételat
mesh_terms: D000368:Aged; D001284:Atrophy; D060825:Cognitive Dysfunction / Q000503:physiopathology*; D005260:Female; D006624:Hippocampus / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000503:physiopathology*