Imaging a memory trace over half a life-time in the medial temporal lobe reveals a time-limited role of CA3 neurons in retrieval
Vanessa Lux,
Erika Atucha,
Takashi Kitsukawa,
Magdalena M Sauvage
Affiliations
Vanessa Lux
Functional Architecture of Memory unit, Mercator Research Group, Medical Faculty, Ruhr University Bochum, Bochum, Germany
Erika Atucha
Functional Architecture of Memory unit, Mercator Research Group, Medical Faculty, Ruhr University Bochum, Bochum, Germany; Functional Neuroplasticity Department, Otto von Guericke University, Magdeburg, Germany; Functional Architecture of Memory Dpt, Leibniz-Institute for Neurobiology, Magdeburg, Germany
Takashi Kitsukawa
Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
Functional Architecture of Memory unit, Mercator Research Group, Medical Faculty, Ruhr University Bochum, Bochum, Germany; Functional Neuroplasticity Department, Otto von Guericke University, Magdeburg, Germany; Functional Architecture of Memory Dpt, Leibniz-Institute for Neurobiology, Magdeburg, Germany
Whether retrieval still depends on the hippocampus as memories age or relies then on cortical areas remains a major controversy. Despite evidence for a functional segregation between CA1, CA3 and parahippocampal areas, their specific role within this frame is unclear. Especially, the contribution of CA3 is questionable as very remote memories might be too degraded to be used for pattern completion. To identify the specific role of these areas, we imaged brain activity in mice during retrieval of recent, early remote and very remote fear memories by detecting the immediate-early gene Arc. Investigating correlates of the memory trace over an extended period allowed us to report that, in contrast to CA1, CA3 is no longer recruited in very remote retrieval. Conversely, we showed that parahippocampal areas are then maximally engaged. These results suggest a shift from a greater contribution of the trisynaptic loop to the temporoammonic pathway for retrieval.
