Allocating, Tagging, and Linking Memories

The formation, stabilization, and editing of memory engrams has been a subject of active research in neuroscience. By comparison, little is known regarding the mechanisms that determine which synapses and neurons (synaptic and neuronal allocation, respectively) go on to encode a given memory. Memory allocation mechanisms are critical for controlling the size of engrams, their strength, longevity, and ultimately how they are linked or related to other engrams. Here, we review recent research of the mechanisms that underlie memory allocation. Specifically, we discuss how mechanisms such as neuronal intrinsic excitability, synaptic tagging and capture, synaptic cross talk, and spine clustering can influence synaptic and neuronal allocation during memory formation. We propose that higher order memory processes, such as memory linking, integration, and inference, are made possible due to specific memory allocation mechanisms that ensure storage in ways that facilitate effective updating and integration at a later time. Finally, we finish by considering the future directions and challenges for memory allocation studies.