Circadian changes in neuronal networks

• Circadian plasticity of the nervous system is generated by the circadian clock.
• Synaptic contacts and morphology of neurons oscillate during the day and night.
• Structural circadian changes lead to cyclic remodeling of brain neuronal networks.
• Network remodeling enables diurnal and nocturnal modes of brain functioning.

The circadian clock generates circadian plasticity in some of the clock and non-clock neurons leading to the daily changes in their structure and in the number of synaptic contacts. This plasticity affects neuronal networks in the brain. The two best known examples of circadian changes in neuronal networks are those observed in the first optic neuropil (lamina) of the fly's visual system and between one group of clock neurons, the small ventral lateral neurons (s-LNvs), and their target cells in the dorsal part of the Drosophila brain. Both of these networks are remodeled in the course of the day by the circadian clock and they are further affected by external stimuli.