Engram neurons: Encoding, consolidation, retrieval, and forgetting of memory

Area of Science:

• Neuroscience
• Cognitive Science
• Molecular Biology

Background:

• The memory engram, the physical trace of memory in the brain, is a rapidly evolving field.
• Recent advances offer insights into how neural populations represent and store memories over time.

Purpose of the Study:

• To synthesize current knowledge on the dynamic changes of memory engram neurons across the memory lifespan.
• To illustrate how engram properties evolve from encoding through consolidation, retrieval, and forgetting.

Main Methods:

• Review and integration of recent experimental findings in memory research.
• Analysis of neurobiological mechanisms underlying memory encoding, consolidation, retrieval, and forgetting.

Main Results:

• Engram neurons undergo significant transformations influenced by cell-intrinsic properties during encoding.
• Encoding neurons are crucial for synaptic and systems-level memory consolidation.
• Changes in engram properties guide neural reactivation during retrieval, facilitating recall.
• Neurobiological mechanisms of forgetting actively counteract established engram properties.

Conclusions:

• The traditional view of the engram needs broadening to include diverse cell-type participation across memory stages.
• A synthesis of general principles governing the dynamic engram across its lifespan is presented.
• Future research directions for understanding the dynamic engram are proposed.