LTS cells in cerebral cortex and their role in generating spike-and-wave oscillations

Some types of epileptic seizures involve both thalamus and cerebral cortex, while other types can be evoked in the cerebral cortex without thalamic participation. We investigated the possible role of low-threshold spike (LTS) cortical neurons in the genesis of these intracortical seizures. We found LTS cortical neurons in cat area 5}7 in vivo, the properties of which could be modeled based on relatively weak densities of the T-type calcium channel. At the network level, a small minority of LTS pyramidal cells was su$cient to generate paroxysmal oscillations with spike-and-wave (SW) "eld potentials. These oscillations reproduce the properties of intracortical SW paroxysms observed in athalamic cats, such as the slow frequency (1.8}2.5 Hz). We suggest that calcium-mediated rebound mechanisms intrinsic to cerebral cortex can explain the genesis of intracortical SW activity. 2001 Elsevier Science B.V. All rights reserved.