Metastability of brain states and the many routes to seizures: Numerous causes, same result

Typical recordings of brain activity, such as electroencephalograms, exhibit an apparent irregularity. Regular, long-lasting periodic activity, is really more characteristic of pathologies like epilepsy. However, it is this randomness in the activity of brain cellular networks that results in the highly variable and adaptable products of brain function, purposeful behaviour probably at the top. We review here some current ideas about the global, coordination dynamics of the neuronal networks of the mammalian brain, and use epileptiform activity as a guide to explore these notions and possible methodologies in the analysis of brain dynamics. We would like to conclude that, at a global level of description, we can formulate conceptual frameworks through which we can comprehend how disparate microscopic events lead to similar macroscopic patterns, apparently organized, of synchronised cellular activity, in normal and pathological brain states. Hence, there may be more than one route to the seizures characteristic of the epilepsies. As reflected from this review, efforts are needed to combine, in a coherent theoretical framework, the integration between the different levels of activity, local and collective, that originate the spatio-temporal patterns of neuronal activity. We hope to provide the reader with a sense of how close or far we are from a unified perspective, and to provoke some lines of inquiry.