Lorenzo Pasquini1, Martin Scherr2, Masoud Tahmasian3, Chun Meng4, Nicholas E Myers5, Marion Ortner6, Mark Mühlau7, Alexander Kurz6, Hans Förstl6, Claus Zimmer4, Timo Grimmer6, Afra M Wohlschläger1, Valentin Riedl3, Christian Sorg8. 1. Department of Neuroradiology, Technische Universität München, Munich, Germany; TUM-Neuroimaging Center, Technische Universität München, Munich, Germany. 2. TUM-Neuroimaging Center, Technische Universität München, Munich, Germany; Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University Salzburg, Salzburg, Austria. 3. Department of Neuroradiology, Technische Universität München, Munich, Germany; TUM-Neuroimaging Center, Technische Universität München, Munich, Germany; Department of Nuclear Medicine, Technische Universität München, Munich, Germany. 4. Department of Neuroradiology, Technische Universität München, Munich, Germany. 5. TUM-Neuroimaging Center, Technische Universität München, Munich, Germany; Department of Experimental Psychology, Oxford University, Oxford, United Kingdom. 6. Department of Psychiatry, Technische Universität München, Munich, Germany. 7. TUM-Neuroimaging Center, Technische Universität München, Munich, Germany; Department of Neurology of Klinikum rechts der Isar, Technische Universität München, Munich, Germany. 8. Department of Neuroradiology, Technische Universität München, Munich, Germany; TUM-Neuroimaging Center, Technische Universität München, Munich, Germany; Department of Psychiatry, Technische Universität München, Munich, Germany. Electronic address: c.sorg@lrz.tum.de.
Abstract
BACKGROUND: The hippocampus (HP) is part of the default mode network (DMN), and both are key targets of Alzheimer's disease (AD). Because of widespread network degeneration, it has been suggested that increasing HP disconnection from the DMN may lead to progressive disinhibition of intra-HP synchronized activity. METHODS: To analyze HP local (i.e., within HP) and global (i.e., within DMN) intrinsic functional connectivity (local/global intrinsic functional connectivity [iFC]), healthy controls and patients with mild cognitive impairment and AD dementia were assessed by spatial high and normal resolution resting-state functional magnetic resonance imaging. RESULTS: Although patients' parietal local-iFC was reduced and positively correlated with reduced global-iFC within the DMN, HP local connectivity was progressively increased and negatively correlated with HP decreased global connectivity. Increased intra-HP connectivity was associated with impaired memory. CONCLUSION: Our result demonstrates a link between increased local and reduced global hippocampal connectivity in AD. Increased intra-HP synchrony may contribute to distinct symptoms such as memory impairment or more speculatively epileptic seizure.
BACKGROUND: The hippocampus (HP) is part of the default mode network (DMN), and both are key targets of Alzheimer's disease (AD). Because of widespread network degeneration, it has been suggested that increasing HP disconnection from the DMN may lead to progressive disinhibition of intra-HP synchronized activity. METHODS: To analyze HP local (i.e., within HP) and global (i.e., within DMN) intrinsic functional connectivity (local/global intrinsic functional connectivity [iFC]), healthy controls and patients with mild cognitive impairment and AD dementia were assessed by spatial high and normal resolution resting-state functional magnetic resonance imaging. RESULTS: Although patients' parietal local-iFC was reduced and positively correlated with reduced global-iFC within the DMN, HP local connectivity was progressively increased and negatively correlated with HP decreased global connectivity. Increased intra-HP connectivity was associated with impaired memory. CONCLUSION: Our result demonstrates a link between increased local and reduced global hippocampal connectivity in AD. Increased intra-HP synchrony may contribute to distinct symptoms such as memory impairment or more speculatively epileptic seizure.
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