The purpose of this paper is to show through the concrete example of epileptic seizure anticipation how neuro-dynamic analysis and “pheno-dynamic” analysis may guide and determine each other. We will show that this dynamic approach to epileptic seizure makes it possible to consolidate the foundations of a cognitive non pharmacological therapy of epilepsy. We will also show through this example how the neuro-phenomenological co-determination could shed new light on the difficult problem of the “gap” which separates subjective experience from neurophysiological (...) activity. (shrink)

The quantification of phase synchrony between neuronal signals is of crucial importance for the study of large-scale interactions in the brain. Two methods have been used to date in neuroscience, based on two distinct approaches which permit a direct estimation of the instantaneous phase of a signal [Phys. Rev. Lett. 81 (1998) 3291; Human Brain Mapping 8 (1999) 194]. The phase is either estimated by using the analytic concept of Hilbert transform or, alternatively, by convolution with a complex wavelet. In (...) both methods the stability of the instantaneous phase over a window of time requires quantification by means of various statistical dependence parameters (standard deviation, Shannon entropy or mutual information). The purpose of this paper is to conduct a direct comparison between these two methods on three signal sets: (1) neural models; (2) intracranial signals from epileptic patients; and (3) scalp EEG recordings. Levels of synchrony that can be considered as reliable are estimated by using the technique of surrogate data. Our results demonstrate that the differences between the methods are minor, and we conclude that they are fundamentally equivalent for the study of neuroelectrical signals. This offers a common language and framework that can be used for future research in the area of synchronization. © 2001 Published by Elsevier Science B.V. (shrink)

Neurophenomenology (Varela 1996) is not only philosophical but also empirical and experimental. Our purpose in this article is to illustrate concretely the efficiency of this approach in the field of neuroscience and, more precisely here, in epileptology. A number of recent observations have indicated that epileptic seizures do not arise suddenly simply as the effect of random fluctuations of brain activity, but require a process of pre-seizure changes that start long before. This has been reported at two different levels of (...) description: on the one hand, the epileptic patient often experiences some warning symptoms that precede seizures from several minutes to hours in the form of very specific lived events. On the other hand, the analyses of brain electrical activities have provided strong evidence that it is possible to detect a pre-seizure state in the neuronal dynamics several minutes before the electro-clinical onset of a seizure. We review here some of the ongoing work of our research group concerning seizure anticipation. In particular, we discuss experimental evidence of upward (local-to-global) formation of conscious experience and its neural substrate, but also of the downward (global-to-local) determination of local neuronal activity by situated conscious activity and its substrate large-scale neural assemblies. This causal role of conscious experience may lead to new kinds of therapy for epileptic patients. (shrink)