[
Nature,
1998]
Bilaterally symmetrical animals must be able to integrate sensory inputs and coordinate motor control on both sides of the body. Thus, many neurons in the central nervous system (CNS) project their axons to the opposite side of the body, whereas others project axons that remain on the same side. In the latest issues of Cell and Neuron, the groups of Corey Goodman, Guy Tear, Marc Tessier-Lavigne and Cori Bargmann report that, from worms and flies to rats and humans, a common mechanism determines which axons cross the midline and which do not.