title: Increased functional connectivity in the default mode network in mild cognitive impairment: a maladaptive compensatory mechanism associated with poor semantic memory performance.
abstract: Semantic memory decline and changes of default mode network (DMN) connectivity have been reported in mild cognitive impairment (MCI). Only a few studies, however, have investigated the role of changes of activity in the DMN on semantic memory in this clinical condition. The present study aimed to investigate more extensively the relationship between semantic memory impairment and DMN intrinsic connectivity in MCI. Twenty-one MCI patients and 21 healthy elderly controls matched for demographic variables took part in this study. All participants underwent a comprehensive semantic battery including tasks of category fluency, visual naming and naming from definition for objects, actions and famous people, word-association for early and late acquired words and reading. A subgroup of the original sample (16 MCI patients and 20 healthy elderly controls) was also scanned with resting state functional magnetic resonance imaging and DMN connectivity was estimated using a seed-based approach. Compared with healthy elderly, patients showed an extensive semantic memory decline in category fluency, visual naming, naming from definition, words-association, and reading tasks. Patients presented increased DMN connectivity between the medial prefrontal regions and the posterior cingulate and between the posterior cingulate and the parahippocampus and anterior hippocampus. MCI patients also showed a significant negative correlation of medial prefrontal gyrus connectivity with parahippocampus and posterior hippocampus and visual naming performance. Our findings suggest that increasing DMN connectivity may contribute to semantic memory deficits in MCI, specifically in visual naming. Increased DMN connectivity with posterior cingulate and medio-temporal regions seems to represent a maladaptive reorganization of brain functions in MCI, which detrimentally contributes to cognitive impairment in this clinical population.
authors.affiliation: Department of Neurosciences, University of Parma, Parma, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Gardini
authors.affiliation: Department of Neuroscience, University of Sheffield, United Kingdom & IRCCS, Fondazione Ospedale San Camillo, Venice, Italy.
authors.forename: Annalena
authors.initials: A
authors.lastname: Venneri
authors.affiliation: Brain Center for Motor and Social Cognition, Istituto Italiano di Tecnologia, Parma, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Sambataro
authors.affiliation: Department of Psychology, University of Oviedo, Oviedo, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Cuetos
authors.affiliation: Department of Neurosciences, University of Parma, Parma, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Fasano
authors.affiliation: Department of Neurosciences, University of Parma, Parma, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Marchi
authors.affiliation: Neuroradiology Unit, Azienda Ospedaliero-Universitaria of Parma, Parma, Italy.
authors.forename: Girolamo
authors.initials: G
authors.lastname: Crisi
authors.affiliation: Department of Neurosciences, University of Parma, Parma, Italy Centre of Cognitive Disorders, AUSL, Parma, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Caffarra
mesh_terms: D000368:Aged; D001921:Brain / Q000098:blood supply / Q000473:pathology*; D001931:Brain Mapping; D060825:Cognitive Dysfunction / Q000150:complications / Q000473:pathology / Q000523:psychology; D005260:Female; D005790:General Adaptation Syndrome / Q000209:etiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000209:etiology*; D008875:Middle Aged; D009415:Nerve Net / Q000098:blood supply / Q000502:physiology; D009434:Neural Pathways / Q000098:blood supply / Q000502:physiology*; D009483:Neuropsychological Tests; D012660:Semantics
keywords: Alzheimer's disease; default mode network; functional MRI resting state; mild cognitive impairment; semantic memory