Editorial: Changes in Molecular Expression After Memory Acquisition and Plasticity. Looking for the Memory Trace

FREUDENTHAL, RAMIRO A. M.; ROMANO, ARTURO; BAEZ, MARIA VERONICA

Frontiers in Molecular Neuroscience

Frontiers

Lugar: Lausane; Año: 2020 vol. 13 p. 1 - 50

Since Semon defined an engram as the neural substrate for memories (Semon, 1921, 1923), several hypotheses have been established, which had tried to determine how an engram is codified and where it is located in different brain structures. Historically, memory trace was defined as the physical mark of an acquired memory that in turn was considered a process divided in stages: acquisition, consolidation, and retrieval. The definition of the physical mark is central to understanding memory processing and helped to establish different scales at which these processes have been studied. Substantial support from research in several model systems points to the synaptic changes that occur initially during memory acquisition and consolidation and also during reconsolidation and extinction. Those changes, led to neurons to interact in a coordinate way that was called, neural assemblies. These assemblies are groups of cells that respond to specific stimulus in a coordinate way with a unique spatiotemporal pattern of firing. Based on that, it would be possible that neural assemblies would define the engram, as the physical mark of a memory (Nicolelis et al., 1997). Nevertheless, non-synaptic mechanisms have been described that are also capable of acting as memory substrates (Abraham et al., 2019). In this context, epigenetic intrinsic cellular adaptations emerge as a possible mechanism that regulate the pattern of RNA transcription and possibly indirectly other molecular dynamics that could initiate the engram at the intracellular level.