Development of layers, maps and modules.

Developing neuronal cell sheets acquire position-specific features by mechanisms that differ in radial and tangential dimensions. These features include guiding cues for axonal growth and targeting that are used, for example, in map formation. Recent evidence supports the notion that graded distributions of molecules are involved in growth cone navigation and axonal branching. In addition, activity-dependent processes are important determinants of functional architecture, especially with respect to modular organization.