Synaptic modifications in learning and memory - A dendritic spine story

Abstract

Synapses are specialized sites where neurons connect and communicate with each other. Activity-dependent modification of synaptic structure and function provides a mechanism for learning and memory. The advent of high-resolution time-lapse imaging in conjunction with fluorescent biosensors and actuators enables researchers to monitor and manipulate the structure and function of synapses both in vitro and in vivo. This review focuses on recent imaging studies on the synaptic modification underlying learning and memory.

Keywords: Dendritic spine; LTD; LTP; Learning; Memory; Synapse.

Figure 1.

Illustration of learning-related spine dynamics. The animal is trained on a learning task (Task 1). (A) Learning is accompanied by elevated spine formation beyond the basal level. (B) If the animal does not learn, basal level spine dynamics persist. (C) Consolidation of learned Task 1 preferentially stabilizes learning-related new spines and eliminates some pre-existing spines at an elevated rate. Thus, learning only transiently increases spine density, but rewires the neural circuit. Furthermore, new spines tend to emerge in clusters, which likely promotes their subsequent survival. (D) Learning and consolidation of a different task (Task 2) induces the formation and stabilization of a new set of spines. (E) Selectively shrinking Task 2-related spines by optogenetic actuators disrupts Task 2 performance. Inset: a new spine shares the same presynaptic bouton with an existing spine, resulting in a multispine bouton (MSB).