Resting-State Connectivity of the Left Frontal Cortex to the Default Mode and Dorsal Attention Network Supports Reserve in Mild Cognitive Impairment

• Published in: Frontiers in aging neuroscience 2017-08, Vol.9, p.264-264
• Main Authors: Franzmeier, Nicolai, Göttler, Jens, Grimmer, Timo, Drzezga, Alexander, Áraque-Caballero, Miguel A, Simon-Vermot, Lee, Taylor, Alexander N W, Bürger, Katharina, Catak, Cihan, Janowitz, Daniel, Müller, Claudia, Duering, Marco, Sorg, Christian, Ewers, Michael
• Format: Article
• Language: English
• Subjects: Age; Atrophy; Attention; Brain mapping; Brain research; Brodmann's area; Cognition & reasoning; Cognitive ability; cognitive reserve; Cortex (frontal); Dementia; Disease; Education; frontoparietal control network; functional connectivity; Functional magnetic resonance imaging; Gender; Hippocampus; Hypotheses; Medical imaging; Memory; mild cognitive impairment; Neural networks; Neuroscience; Older people; Pathology; Visual cortex; Visual perception
• ISSN: 1663-4365; 1663-4365
• DOI: 10.3389/fnagi.2017.00264

Reserve refers to the phenomenon of relatively preserved cognition in disproportion to the extent of neuropathology, e.g., in Alzheimer's disease. A putative functional neural substrate underlying reserve is global functional connectivity of the left lateral frontal cortex (LFC, Brodmann Area 6/44). Resting-state fMRI-assessed global LFC-connectivity is associated with protective factors (education) and better maintenance of memory in mild cognitive impairment (MCI). Since the LFC is a hub of the fronto-parietal control network that regulates the activity of other networks, the question arises whether LFC-connectivity to specific networks rather than the whole-brain may underlie reserve. We assessed resting-state fMRI in 24 MCI and 16 healthy controls (HC) and in an independent validation sample (23 MCI/32 HC). Seed-based LFC-connectivity to seven major resting-state networks (i.e., fronto-parietal, limbic, dorsal-attention, somatomotor, default-mode, ventral-attention, visual) was computed, reserve was quantified as residualized memory performance after accounting for age and hippocampal atrophy. In both samples of MCI, LFC-activity was anti-correlated with the default-mode network (DMN), but positively correlated with the dorsal-attention network (DAN). Greater education predicted stronger LFC-DMN-connectivity (anti-correlation) and LFC-DAN-connectivity. Stronger LFC-DMN and LFC-DAN-connectivity each predicted higher reserve, consistently in both MCI samples. No associations were detected for LFC-connectivity to other networks. These novel results extend our previous findings on global functional connectivity of the LFC, showing that LFC-connectivity specifically to the DAN and DMN, two core memory networks, enhances reserve in the memory domain in MCI.