NEURONAL DOMAINS IN DEVELOPING NEOCORTEX - MECHANISMS OF COACTIVATION

The mammalian neocortex consists of columnar circuits, whose developme nt may be controlled by patterns of spontaneous activity. Columnar dom ains of spontaneously coactive neurons were previously described using Ca2+ imaging of slices from developing rat neocortex. We have now inv estigated the cellular mechanisms responsible for the coactivation of these domains. The activation starts in the center of a domain and spr eads at speeds of approximately 100 mu m/s. Domains occur in the prese nce of tetrodotoxin but are blocked by the gap junction blockers halot hane and octanol. Simultaneous intracellular and optical recordings fr om dye-coupled cells reveal functional coupling between developing neo cortical neurons. These data support the hypothesis that a neuronal do main results from the spontaneous excitation of one or a few trigger n eurons that subsequently activate, either electrically or biochemicall y, the rest of the cells via gap junctions.