A network of fast-spiking cells in the neocortex connected by electrical synapses

Encoding of information in the cortex is thought to depend on synchronous f iring of cortical neurons(1,2). Inhibitory neurons are known to be critical in the coordination of cortical activity(3-5), but how interaction among i nhibitory cells promotes synchrony is not well understood(4,6-12). To addre ss this issue directly, we have recorded simultaneously from pairs of fast- spiking (FS) cells, a type of gamma-aminobutyric acid (GABA)-containing neo cortical interneuron(13). Here we report a high occurrence of electrical co upling among FS cells. Electrical synapses were not found among pyramidal n eurons or between FS cells and other cortical cells. Some FS cells were int erconnected by both electrical and GABAergic synapses. We show that communi cation through electrical synapses allows excitatory signalling among inhib itory cells and promotes their synchronous spiking. These results indicate that electrical synapses establish a network of fast-spiking cells in the n eocortex which may play a key role in coordinating cortical activity.