Changes in the molecular composition and strength of synaptic connections are thought to underlie learning-related plasticity in the brain. These activity-dependent modifications in synaptic strength utilize a variety of cellular and molecular mechanisms, many of which control the abundance of receptors in the postsynaptic membrane and the structure of dendritic spines. These structural and functional changes are driven by the activation of Ca²⁺-dependent signaling cascades that engage membrane trafficking pathways, influence the lateral diffusion and trapping of receptors in the postsynaptic density, and alter the morphology of dendritic spines. Numerous methods have been developed to visualize these synaptic changes in both tissue preparations and in vivo during learning. These powerful imaging approaches have provided fundamental insights into the processes that drive learning-related synaptic plasticity.

This methods collection includes common approaches to probe functional changes at synapses (live-cell imaging of pH-sensitive fluorescent proteins fused to receptor subunits, genetically encoded calcium indicators, and FRET-based sensors of intracellular signaling pathway) and structural changes (live-cell imaging of dendritic spines, TimeSTAMP, mGRASP, and super-resolution imaging of the postsynaptic machinery), as well as methods to measure the mobility of receptors, signaling factors, and scaffold proteins in spines and dendrites (single-particle tracking and photobleaching/photoactivation experiments).