Eur. Phys. J. Special Topics 227, 883–893 (2018)
https://doi.org/10.1140/epjst/e2018-800015-1

Regular Article

Synchronization structure of evolving epileptic networks using cross-entropy

¹ Instituto de Matemática e Estatística, Universidade de São Paulo, São Paulo, Brazil
² Hospital Israelita Albert Einstein, São Paulo, Brazil
³ São Paulo State University (UNESP), Instituto de Física Teórica, São Paulo, Brazil
⁴ Epistemic, Department of Research, São Paulo, Brazil

^a e-mail: birasm@gmail.com

Received: 1 February 2018
Received in final form: 27 April 2018
Published online: 19 October 2018

Abstract

In this paper we present connectivity patterns of evolving large scale epileptic networks. We employed a cross-entropy measure in the frequency domain on EEG signals to infer the networks, before and during episodes of epileptic seizures. This measure allowed us to make a richer portrait about the node interactions on the graph and to identify emergent structures associated with the synchronization of brain activity. Our results points to a more complex scenario of network organization than the synchronized/unsynchronized dichotomy, with two main results: first, showing regions with unsynchronized (or independent) behavior, even during absence seizures, contradicting the concept of hypersynchrony. Furthermore, we explore the cross-entropy fluctuations along the seizure: a group of nodes became more similar over time while another group became more different, showing a complementary behaviour and different local brain activities. These results bring new questions about the spreading and the sustenance of the epileptic seizures and others synchronization phenomena in living systems.