Retinal ganglion cells project to the thalamus and superior colliculus, where their axonal terminals form orderly topographic maps. There is converging evidence that, during development, correlated impulse activity and competition between axonal inputs for postsynaptic targets are essential for establishing orderly sets of connections. In simultaneous recordings from 100 ganglion cells in the neonatal cat retina, slow waves of correlated impulses are found even before photoreceptors are present. These waves of electrical activity could provide the spatiotemporal correlations needed to create topographical projections in the brain.

C.J. Shatz, "Impulse activity and the patterning of connections during CNS development," Neuron, 5, 745-56, December 1990. (Stanford University School of Medicine, Calif.)

The barn owl can localize sound sources. Two pathways carrying information about sound have been traced into the brain of the owl, one computing interaural time differences and the other analyzing interaural amplitude differences. These two streams are combined to create...

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