FIGURE 1.

Schematic diagram of reentrant white-matter fiber bundles linking distant cortical areas. Gray triangles represent pyramidal neurons that comprise the bulk of neocortical gray matter. For clarity, the dense packing of axonal and dendritic arbors that link neurons within the cortical gray matter is not shown. Colored filled circles represent excitatory neurons projecting axons that send reentrant action potentials bidirectionally between areas. Colored arrowheads represent presynaptic terminals of these axons. AP→ indicates direction of signaling.