20 ms

20 ms

FIGURE 7—1 Intracellular counterparts of spike-wave discharges (SWDs) in GAERS model of absence epilepsy. A: Electroencephalographic (EEG) recording of spontaneous SWDs. B: Schematic diagram of the thalamocortical network. The different colors of neuronal cell types also apply to the intracellular in vivo traces recorded during SWDs in C-E: Green, neurons of reticular thalamic (RT) nucleus; blue, thalamocortical (TC) neuron of the ventrobasal thalamus; red. neuron of the cortical layer V. C: Layer V cortical neurons reveal rhythmic depolarizations, which elicit one to three action potentials, superimposed on a long-lasting hyperpolarization. D: In reticular thalamic (RT) neurons, SWD-associated activity starts with a hyperpolarization (see expanded trace bottom left), followed by rhythmic generation of low-threshold Ca2+ spikes (LTSs) associated with bursts of action potentials (see expanded trace bottom right). Note that excitatory postsynaptic potentials (EPSPs) lead to the generation of a LTS. E: Thalamocortical (TC) neurons of the ventrobasal thalamus show rhythmic sequences of EPSP and inhibitory postsynaptic potentials (IPSPs), with occasional firing of action potentials. An EPSP/IPSP sequence is expanded in the bottom panel. (C-E adapted, with permission, from Crunelli and Leresche, 2002.)

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