Periodic Reporting for period 1 - REMGRAM (Unlocking the secrets of remote memories: dissecting the cortico-hippocampal engram)
Okres sprawozdawczy: 2024-05-01 do 2026-04-30
Podsumowanie kontekstu i ogólnych celów projektu
REMGRAM is a neuroscience research project that investigates how the brain decides which parts of an experience are stored as long-term memories and which are progressively forgotten. Understanding these mechanisms is essential because memory dysfunction is a central feature of neurological and psychiatric disorders such as Alzheimer’s disease and post-traumatic stress disorder (PTSD), which affect millions of people in Europe.
When people remember an event after a long period of time, they usually retain only its most meaningful or emotional aspects, while many details disappear. Although scientists already know a great deal about how memories are initially formed, it is still unclear why some components of an experience survive over time while others fade away. REMGRAM aims to answer this question by studying how different groups of neurons contribute to the formation of recent and remote memories.
The project focuses on “engrams”, which are groups of neurons activated during an experience and believed to physically store memories in the brain. Previous research has shown that memories are initially dependent on the hippocampus, a brain region involved in episodic memory, and later become more dependent on cortical regions associated with long-term and generalized memory storage. However, the biological mechanisms that determine which specific aspects of an experience are transferred into long-lasting cortical memories remain unknown.
To address this challenge, REMGRAM uses a cutting-edge optogenetic technology called FLiCRE. This method allows researchers to label and manipulate neurons that are active during very precise moments of an experience, with a temporal resolution of only a few seconds. Unlike previous technologies, which could only identify neurons active over long periods of time, FLiCRE makes it possible to distinguish between different neuronal populations involved in separate components of the same event.
Using mouse models of contextual fear memory, REMGRAM will identify neurons activated during specific behavioral phases (exploration, shock-delivery, freezing behavior and others). The project will investigate whether these distinct neuronal populations contribute differently to the formation of recent memories and long-term remote memories.
The research combines several advanced neuroscience techniques, including optogenetics, calcium imaging, behavioral analysis, histology, and computational neuroscience. Real-time behavioral tracking systems will be used to selectively label neurons during specific actions performed by the animals. Subsequently, neuronal activity will be monitored and manipulated to determine how individual memory components are stored, stabilized, generalized, or forgotten over time.
Beyond its scientific importance, REMGRAM has significant societal relevance. Better understanding of how memories are selected and stabilized in the brain could support the future development of therapies aimed at preventing memory loss or reducing maladaptive memory persistence in neurological and psychiatric disorders. The findings may contribute to future non-invasive strategies to improve cognitive health and quality of life in ageing populations and patients affected by memory-related diseases.
The project also contributes to methodological innovation in neuroscience by demonstrating the use of highly precise neuronal labeling technologies to study memory processes. These approaches could later be applied to other areas of behavioral and brain research.
REMGRAM strongly supports open science practices. Research results, protocols, and publications will be made openly accessible through open-access journals, preprint servers, and public repositories. The project also includes communication and outreach activities designed to increase public awareness of neuroscience research, brain health, and the importance of animal models in biomedical science.
Overall, REMGRAM aims to generate new knowledge about the biological foundations of memory persistence and forgetting, while also developing innovative tools and approaches that may benefit the broader neuroscience community and future translational research.
When people remember an event after a long period of time, they usually retain only its most meaningful or emotional aspects, while many details disappear. Although scientists already know a great deal about how memories are initially formed, it is still unclear why some components of an experience survive over time while others fade away. REMGRAM aims to answer this question by studying how different groups of neurons contribute to the formation of recent and remote memories.
The project focuses on “engrams”, which are groups of neurons activated during an experience and believed to physically store memories in the brain. Previous research has shown that memories are initially dependent on the hippocampus, a brain region involved in episodic memory, and later become more dependent on cortical regions associated with long-term and generalized memory storage. However, the biological mechanisms that determine which specific aspects of an experience are transferred into long-lasting cortical memories remain unknown.
To address this challenge, REMGRAM uses a cutting-edge optogenetic technology called FLiCRE. This method allows researchers to label and manipulate neurons that are active during very precise moments of an experience, with a temporal resolution of only a few seconds. Unlike previous technologies, which could only identify neurons active over long periods of time, FLiCRE makes it possible to distinguish between different neuronal populations involved in separate components of the same event.
Using mouse models of contextual fear memory, REMGRAM will identify neurons activated during specific behavioral phases (exploration, shock-delivery, freezing behavior and others). The project will investigate whether these distinct neuronal populations contribute differently to the formation of recent memories and long-term remote memories.
The research combines several advanced neuroscience techniques, including optogenetics, calcium imaging, behavioral analysis, histology, and computational neuroscience. Real-time behavioral tracking systems will be used to selectively label neurons during specific actions performed by the animals. Subsequently, neuronal activity will be monitored and manipulated to determine how individual memory components are stored, stabilized, generalized, or forgotten over time.
Beyond its scientific importance, REMGRAM has significant societal relevance. Better understanding of how memories are selected and stabilized in the brain could support the future development of therapies aimed at preventing memory loss or reducing maladaptive memory persistence in neurological and psychiatric disorders. The findings may contribute to future non-invasive strategies to improve cognitive health and quality of life in ageing populations and patients affected by memory-related diseases.
The project also contributes to methodological innovation in neuroscience by demonstrating the use of highly precise neuronal labeling technologies to study memory processes. These approaches could later be applied to other areas of behavioral and brain research.
REMGRAM strongly supports open science practices. Research results, protocols, and publications will be made openly accessible through open-access journals, preprint servers, and public repositories. The project also includes communication and outreach activities designed to increase public awareness of neuroscience research, brain health, and the importance of animal models in biomedical science.
Overall, REMGRAM aims to generate new knowledge about the biological foundations of memory persistence and forgetting, while also developing innovative tools and approaches that may benefit the broader neuroscience community and future translational research.
Prace wykonane od początku projektu do końca okresu sprawozdawczego oraz najważniejsze dotychczasowe rezultaty
During the project, the planned experimental platform based on FLiCRE technology was successfully established and optimized to investigate how distinct neuronal populations contribute to recent and remote memory storage. The work focused on identifying and manipulating specific engram subpopulations activated during different phases of contextual fear memory formation.
The project implemented a combination of advanced behavioral neuroscience techniques, including FLiCRE-based neuronal tagging, optogenetics, calcium imaging, stereotactic surgeries, histology, and computational analysis of neuronal activity. Behavioral protocols for contextual fear conditioning and memory generalization were optimized and standardized to ensure reliable identification of neuronal populations associated with distinct behavioral components of memory acquisition.
Using FLiCRE, neuronal ensembles activated during specific moments of memory encoding were selectively labeled and manipulated with high temporal precision. This approach enabled the identification of neuronal populations associated with pre-shock, shock, and freezing phases of contextual fear conditioning in both the hippocampal CA1 region and the anterior cingulate cortex (ACC).
One of the major scientific achievements of the project was the demonstration that while recent memory recall strongly depends on shock-responsive neuronal populations located in the hippocampus (Pouget et al., 2026), at remote time points, memory retrieval showed a functional shift toward cortical circuits, particularly involving the ACC. These findings provide direct evidence for a dynamic reorganization of memory representations across brain regions over time.
Importantly, the project demonstrated that both pre-shock and shock-responsive neuronal populations are sufficient and necessary for memory recall at remote time points in the ACC. Through optogenetic manipulation of FLiCRE-labeled cells, activation of these neuronal ensembles was able to induce memory-related behavioral responses, while their inhibition impaired memory expression. These results support the hypothesis that distinct subpopulations of engram cells contribute differentially to memory persistence and retrieval.
The calcium imaging component of the project was also successfully implemented and optimized. In vivo recordings revealed the presence of distinct neuronal populations corresponding to pre-shock, shock, and freezing-responsive cells in both CA1 and ACC during memory processing. These experiments provided real-time characterization of neuronal activity dynamics associated with different behavioral components of fear memory.
In parallel, the project established optimized pipelines for calcium imaging acquisition and analysis, including data preprocessing, neuronal activity extraction, and behavioral alignment. Histological protocols and imaging procedures were also refined to support accurate identification and quantification of tagged neuronal populations.
Overall, the project achieved its main technical objectives by establishing and validating a novel experimental framework capable of dissecting memory engrams with high temporal specificity. The results generated important new knowledge about how different neuronal subpopulations contribute to the transition from recent hippocampus-dependent memories to remote cortical memories. These findings represent a significant advancement in the understanding of memory consolidation and systems-level memory reorganization in the brain.
The project implemented a combination of advanced behavioral neuroscience techniques, including FLiCRE-based neuronal tagging, optogenetics, calcium imaging, stereotactic surgeries, histology, and computational analysis of neuronal activity. Behavioral protocols for contextual fear conditioning and memory generalization were optimized and standardized to ensure reliable identification of neuronal populations associated with distinct behavioral components of memory acquisition.
Using FLiCRE, neuronal ensembles activated during specific moments of memory encoding were selectively labeled and manipulated with high temporal precision. This approach enabled the identification of neuronal populations associated with pre-shock, shock, and freezing phases of contextual fear conditioning in both the hippocampal CA1 region and the anterior cingulate cortex (ACC).
One of the major scientific achievements of the project was the demonstration that while recent memory recall strongly depends on shock-responsive neuronal populations located in the hippocampus (Pouget et al., 2026), at remote time points, memory retrieval showed a functional shift toward cortical circuits, particularly involving the ACC. These findings provide direct evidence for a dynamic reorganization of memory representations across brain regions over time.
Importantly, the project demonstrated that both pre-shock and shock-responsive neuronal populations are sufficient and necessary for memory recall at remote time points in the ACC. Through optogenetic manipulation of FLiCRE-labeled cells, activation of these neuronal ensembles was able to induce memory-related behavioral responses, while their inhibition impaired memory expression. These results support the hypothesis that distinct subpopulations of engram cells contribute differentially to memory persistence and retrieval.
The calcium imaging component of the project was also successfully implemented and optimized. In vivo recordings revealed the presence of distinct neuronal populations corresponding to pre-shock, shock, and freezing-responsive cells in both CA1 and ACC during memory processing. These experiments provided real-time characterization of neuronal activity dynamics associated with different behavioral components of fear memory.
In parallel, the project established optimized pipelines for calcium imaging acquisition and analysis, including data preprocessing, neuronal activity extraction, and behavioral alignment. Histological protocols and imaging procedures were also refined to support accurate identification and quantification of tagged neuronal populations.
Overall, the project achieved its main technical objectives by establishing and validating a novel experimental framework capable of dissecting memory engrams with high temporal specificity. The results generated important new knowledge about how different neuronal subpopulations contribute to the transition from recent hippocampus-dependent memories to remote cortical memories. These findings represent a significant advancement in the understanding of memory consolidation and systems-level memory reorganization in the brain.
Innowacyjność oraz oczekiwany potencjalny wpływ (w tym dotychczasowe znaczenie społeczno-gospodarcze i szersze implikacje społeczne projektu)
REMGRAM advanced the understanding of how different components of a memory are selectively stored and reorganized across brain regions over time. While previous studies showed that recent memories rely on the hippocampus and remote memories progressively recruit cortical regions, the precise neuronal populations underlying this transition were still unknown.
The project went beyond the state of the art by using FLiCRE technology to label and manipulate neuronal populations with second-scale temporal precision during specific phases of memory acquisition. This allowed, for the first time, the identification of distinct pre-shock, shock, and freezing-responsive engram cells in the ACC within the same behavioral task at remote time points.
Using this approach, the project demonstrated that recent memory recall depends primarily on shock-responsive hippocampal neurons, while remote memory retrieval progressively shifts toward ACC-dependent cortical representations. Importantly, both pre-shock and shock neuronal populations were shown to be sufficient and necessary for memory recall through selective optogenetic manipulation of FLiCRE-tagged cells.
The project also established optimized protocols for behavioral testing, FLiCRE-based tagging, calcium imaging recordings, and neuronal activity analysis. Calcium imaging experiments confirmed the presence of distinct pre-shock, shock, and freezing neuronal populations in both CA1 and ACC.
These findings provide new mechanistic insight into systems memory consolidation and establish a novel experimental framework for studying memory engrams with high temporal precision. The results may contribute in the future to research on memory-related disorders such as PTSD and Alzheimer’s disease by improving understanding of how memories are stabilized, generalized, or lost over time.
The project went beyond the state of the art by using FLiCRE technology to label and manipulate neuronal populations with second-scale temporal precision during specific phases of memory acquisition. This allowed, for the first time, the identification of distinct pre-shock, shock, and freezing-responsive engram cells in the ACC within the same behavioral task at remote time points.
Using this approach, the project demonstrated that recent memory recall depends primarily on shock-responsive hippocampal neurons, while remote memory retrieval progressively shifts toward ACC-dependent cortical representations. Importantly, both pre-shock and shock neuronal populations were shown to be sufficient and necessary for memory recall through selective optogenetic manipulation of FLiCRE-tagged cells.
The project also established optimized protocols for behavioral testing, FLiCRE-based tagging, calcium imaging recordings, and neuronal activity analysis. Calcium imaging experiments confirmed the presence of distinct pre-shock, shock, and freezing neuronal populations in both CA1 and ACC.
These findings provide new mechanistic insight into systems memory consolidation and establish a novel experimental framework for studying memory engrams with high temporal precision. The results may contribute in the future to research on memory-related disorders such as PTSD and Alzheimer’s disease by improving understanding of how memories are stabilized, generalized, or lost over time.