The importance of hippocampal dynamic connectivity in explaining memory function in multiple sclerosis. Issue 5 (30th March 2018)

• Record Type: Journal Article
• Authors: van Geest, Quinten; Hulst, Hanneke E.; Meijer, Kim A.; Hoyng, Lieke; Geurts, Jeroen J.G.; Douw, Linda
• Is Part Of: Brain and behavior. Volume 8:Issue 5(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-03-30
• Subjects: cognition -- dynamic functional connectivity -- functional magnetic resonance imaging -- hippocampus -- memory -- multiple sclerosis; Neurology -- Periodicals; Neurosciences -- Periodicals; Psychology -- Periodicals; Psychiatry -- Periodicals; 616.8005
• DOI: 10.1002/brb3.954
• Languages: English
• ISSNs: 2162-3279

Abstract

Abstract: Introduction: Brain dynamics (i.e., variable strength of communication between areas), even at the scale of seconds, are thought to underlie complex human behavior, such as learning and memory. In multiple sclerosis (MS), memory problems occur often and have so far only been related to "stationary" brain measures (e.g., atrophy, lesions, activation and stationary (s) functional connectivity (FC) over an entire functional scanning session). However, dynamics in FC (dFC) between the hippocampus and the (neo)cortex may be another important neurobiological substrate of memory impairment in MS that has not yet been explored. Therefore, we investigated hippocampal dFC during a functional (f) magnetic resonance imaging (MRI) episodic memory task and its relationship with verbal and visuospatial memory performance outside the MR scanner. Methods: Thirty‐eight MS patients and 29 healthy controls underwent neuropsychological tests to assess memory function. Imaging (1.5T) was obtained during performance of a memory task. We assessed hippocampal volume, functional activation, and sFC (i.e., FC of the hippocampus with the rest of the brain averaged over the entire scan, using an atlas‐based approach). Dynamic FC of the hippocampus was calculated using a sliding window approach. Results: No group differences were found in hippocampal activation, sFC, and dFC. However, stepwise forward regression analyses in patients revealed that lower dFC of the left hippocampus (standardized β = −0.30; p = .021) could explain an additional 7% of variance (53% in total) in verbal memory, in addition to female sex and larger left hippocampal volume. For visuospatial memory, lower dFC of the right hippocampus (standardized β = −0.38; p = .013) could explain an additional 13% of variance (24% in total) in addition to higher sFC of the right hippocampus. Conclusion: Low hippocampal dFC is an important indicator for maintained memory performance in MS, in addition to other hippocampal imaging measures. Hence, brain dynamics may offer new insights into the neurobiological mechanisms underlying memory (dys)function. Abstract : Dynamic functional connectivity (dFC) of the hippocampus and the (neo)cortex may be an important neurobiological substrate of memory impairment in MS. We investigated the added value of hippocampal dFC on top of traditional MRI measures in explaining verbal and visuospatial memory. We found that lower dFC of the left and right hippocampus was related to better verbal and visuospatial memory performance, respectively, on top of hippocampal volume and stationary functional connectivity.