In Section 1 of this volume, many current concepts in epilepsy research were discussed within the context of intact animal models. In Section 2, the emphasis was on insights from the in-vitro examination of tissue from such models. In this last section, the experimental ‘model’ begins with normal tissue. The investigators have asked, ‘What are the basic cellular properties, present in normal cells and tissue, that could contribute to the generation of abnormal activity?’ These studies provide a lexicon of the ‘mights’ and ‘coulds’ with respect to various forms of epileptiform activities.

The discussions presented in this section provide examples of a variety of different levels of analysis. In the chapters by Wilson & Bragdon (Chapter 11) and by Connors & Amitai (Chapter 12), the emphasis is on local circuitry (the connectivity between neural elements) and a consideration of which elements are critical for the generation of abnormal activities. Connors & Amitai pursue this issue by examining the properties of a given cell type as it relates to the generation of epileptiform activities within the circuit. In Chapter 14 (McBain et al) the focus is on the influence of the extracellular milieu surrounding neurons – how changes in that environment might lead to the transformation from normal to abnormal activities, even in the absence of specific abnormalities within given cell populations.