Cognitive Efficiency in Alzheimer's Disease is Associated with Increased Occipital Connectivity

Matteo De Marco, Davide Duzzi, Francesca Meneghello, Annalena Venneri

Research output: Contribution to journalArticle

Abstract

There are cognitive domains which remain fully functional in a proportion of Alzheimer's disease (AD) patients. It is unknown, however, what distinctive mechanisms sustain such efficient processing. The concept of "cognitive efficiency" was investigated in these patients by operationalizing it as a function of the level of performance shown on the Letter Fluency test, on which, very often, patients in the early stages of AD show unimpaired performance. Forty-five individuals at the prodromal/early stage of AD (diagnosis supported by subsequent clinical follow-ups) and 45 healthy controls completed a battery of neuropsychological tests and an MRI protocol which included resting state acquisitions. The Letter Fluency test was the only task on which no between-group difference in performance was found. Participants were divided into "low-performing" and "high-performing" according to the global median. Dual-regression methods were implemented to compute six patterns of network connectivity. The diagnosis-by-level of performance interaction was inferred on each pattern to determine the network distinctiveness of efficient performance in AD. Significant interactions were found in the anterior default mode network, and in both left and right executive control networks. For all three circuits, high-performing patients showed increased connectivity within the ventral and dorsal part of BA19, as confirmed by post hoc t tests. Peristriate remapping is suggested to play a compensatory role. Since the occipital lobe is the neurophysiological source of long-range cortical connectivity, it is speculated that the physiological mechanisms of functional connectivity might sustain occipital functional remapping in early AD, particularly for those functions which are sustained by areas not excessively affected by the prodromal disease.

Original languageEnglish
Pages (from-to)541-556
Number of pages16
JournalJournal of Alzheimer's Disease
Volume57
Issue number2
DOIs
Publication statusPublished - 2017

Keywords

  • Aged
  • Alzheimer Disease/diagnostic imaging
  • Brain Mapping
  • Cognition/physiology
  • Female
  • Follow-Up Studies
  • Gray Matter/diagnostic imaging
  • Humans
  • Magnetic Resonance Imaging
  • Male
  • Neural Pathways/diagnostic imaging
  • Neuropsychological Tests
  • Occipital Lobe/diagnostic imaging
  • Prodromal Symptoms
  • Rest

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