The brain adapts to the environment in part by persistently modifying and rearranging the diverse synaptic connections between neurons. These changes include strengthening or weakening existing links, as well as forming and eliminating synapses — long-term adjustments that are required for learning and memory.
Since excitatory synapses on excitatory neurons are localized to small protrusions called dendritic spines, earlier studies have used dendritic spine dynamics to monitor excitatory synaptic remodeling in vivo. However, the lack of a morphological surrogate for inhibitory synapses has precluded their observation, and although the interplay between excitatory and inhibitory transmission maintains a critical role in brain plasticity, the inability to monitor inhibitory synapse dynamics has prohibited examination of how they correspond with excitatory changes.