Brain complexity: circadian rhythm (Introduction)

by David Turell , Thursday, November 06, 2014, 18:11 (3452 days ago) @ David Turell

In fruit flies, there are large changes in circadian rhythm:-"In Drosophila, this biological clock comprises 150-200 neurons nestled in seven clusters that include the small ventral lateral (sLNv) neurons. Researchers had known that these circadian pacemakers keep fly brains on a clock by rhythmically releasing chemical cues such as pigment dispensing factor (PDF) and other neurotransmitters. But in a 2008 study, María Fernanda Ceriani of the Leloir Institute in Argentina and colleagues found that these pacemaker cells also remodel their physical connections, forming more-complex ones during the day and significantly simpler circuits at night. The daily structural changes led Ceriani to wonder whether such physical contacts could also communicate time to neurons outside the clock.-"To map synaptic connections, Ceriani and her colleagues labeled neurons with complementary fragments of a fluorescent protein; if two cells formed a synapse, the separate parts of the transmembrane protein snapped together and fluoresced under a microscope. The method, called GRASP, identified potential postsynaptic contacts formed early in the morning by axonal processes from sLNvs reaching out not only to other classes of clock neurons, such as posterior dorsal neuron 1 (DN1p) cells, but to neurons in noncircadian brain regions, such as the mushroom body, lateral horn, and the pars intercerebralis. Those processes then appeared to be pruned back overnight. In contrast, projections to DN1p cells remained constant throughout the day and night, while synapses made with another neuronal cluster were enhanced at night."-http://www.the-scientist.com/?articles.view/articleNo/41277/title/Rhythmic-Rewiring/-Humans probably have similar mechanisms. This requires complex informational planning to develop. This is probably one the patterns followed in animal life development