AUTHOR=Funane Tsukasa , Jun Heechul , Sutoko Stephanie , Saido Takaomi C. , Kandori Akihiko , Igarashi Kei M. TITLE=Impaired sharp-wave ripple coordination between the medial entorhinal cortex and hippocampal CA1 of knock-in model of Alzheimer’s disease JOURNAL=Frontiers in Systems Neuroscience VOLUME=16 YEAR=2022 URL=https://www.frontiersin.org/journals/systems-neuroscience/articles/10.3389/fnsys.2022.955178 DOI=10.3389/fnsys.2022.955178 ISSN=1662-5137 ABSTRACT=

Clinical evidence suggests that the entorhinal cortex is a primary brain area triggering memory impairments in Alzheimer’s disease (AD), but the underlying brain circuit mechanisms remain largely unclear. In healthy brains, sharp-wave ripples (SWRs) in the hippocampus and entorhinal cortex play a critical role in memory consolidation. We tested SWRs in the MEC layers 2/3 of awake amyloid precursor protein knock-in (APP-KI) mice, recorded simultaneously with SWRs in the hippocampal CA1. We found that MEC→CA1 coordination of SWRs, found previously in healthy brains, was disrupted in APP-KI mice even at a young age before the emergence of spatial memory impairments. Intriguingly, long-duration SWRs critical for memory consolidation were mildly diminished in CA1, although SWR density and amplitude remained intact. Our results point to SWR incoordination in the entorhinal-hippocampal circuit as an early network symptom that precedes memory impairment in AD.