About this Research Topic
The term “engram” refers to the physical elements serving learning and memory. A growing body of literature, mainly focusing on hippocampal circuits, has identified and manipulated cellular engrams, which are defined as neurons whose activity is both necessary and sufficient for the establishment of new memories. However, more questions are raised, as researchers strive to define a cellular and, possibly, synaptic code for memory storage and retrieval. Indeed, synaptic plasticity (i.e., potentiation or depression of synaptic transmission) can be considered as a "local" phenomenon, involving a subset of the dendritic spine equipment of a given neuron or neuronal ensemble. In addition, plastic changes can have different magnitudes or polarities among the various dendritic compartments of a neuron.
The current conceptual and experimental approach is based on the manipulation of whole neurons serving engram formation. The "cellular engram" approach has provided fundamental information on the mechanisms of learning and memory, but is limited by its low spatial resolution. Thus, a paradigm shift, allowing a zooming in to "synaptic engrams" is required. This can be accomplished by creating new tools for studying synaptic engrams under multiple points of view: structural, functional, behavioral, “omics”. These tools should be designed with the specific aim of answering the following main questions:
1) Do synaptic engrams established in response to different learning and memory processes (e.g., different behavioral paradigms) have a different distribution?
2) Do synaptic engrams created in different brain areas share common functional/morphological/molecular principles?
3) Do synaptic engrams have a specific molecular or functional fingerprint?
4) Do different neuronal types have a specific role in engram formation?
5) Do neurons collaborate with other cell types in establishing engrams?
6) How do neurological and neurodegenerative pathologies affect synaptic engrams?
Our Research Topic will gather contributions from Experts in the study of learning and memory to providing a comprehensive overview of the state of the art of research on memory engrams. Contributions employing diverse approaches, namely molecular biology, imaging, proteomics, transcriptomics, optogenetics and electrophysiology are encouraged and welcome. In addition, selected reviews of the current literature on engrams and memory will be accepted.
The ideal contribution should be focusing on the application of the technical approaches outlined above to the study of memory engrams, thus adding new bricks to the building of our knowledge on the mechanisms serving the creation and maintenance of the physical information storage units of the brain.
Keywords: cFos, Arc, fluorescent proteins, optogenetics, dendritic spines, synapse potentiation
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