WHAT STOPS SYNCHRONIZED THALAMOCORTICAL OSCILLATIONS

Slow-wave sleep as well as generalized absence seizures are characteri zed by the occurrence of synchronized oscillations in thalamocortical systems that spontaneously appear and disappear. The spontaneous appea rance of synchronized oscillations results from the initiation by one or a small number of cells followed by the progressive recruitment of large numbers of neighboring neurons into the synchronized network act ivity. Synchronized network oscillations representative of slow-wave s leep, as well as absence seizures, were demonstrated to cease spontane ously at least in part through the persistent activation of a hyperpol arization-activated cation conductance, Block of this conductance resu lted in oscillations that, once generalized, occur continuously. These results indicate that the persistent activation of a hyperpolarizatio n-activated cation conductance is a key mechanism through which synchr onized oscillations in thalamocortical networks normally terminate.