Long-Term In Vivo Imaging of Structural Plasticity in Rodents

Morphological changes, emergence, and elimination of individual synapses are referred to as structural plasticity. Structural plasticity represents a basic process that enables neurons to strengthen or weaken their connectivity to neighboring neurons. Thereby, neuronal networks preserve their ability to change their wiring in response to external stimuli. To monitor structural plasticity of synapses, two-photon in vivo imaging has become an invaluable tool. The combination of two-photon microscopy, installation of cranial windows, and fluorescent proteins allows to monitor structural plasticity in live animals repetitively over periods of hours, days, weeks, months, and even more than a year. Initial studies investigated superficial brain regions such as the somatosensory, visual cortex, or olfactory bulb. More recently, also deeper brain regions such as the hippocampus have been made accessible by the development of specialized surgeries and optics. The current chapter will introduce the relevant techniques and surgery procedures to carry out repetitive long-term in vivo imaging in rodents.