Thalamic deactivation at sleep onset precedes that of the cerebral cortex in humans.

Thalamic and cortical activities are assumed to be time-locked throughout all vigilance states. Using simultaneous intracortical and intrathalamic recordings, we demonstrate here that the thalamic deactivation occurring at sleep onset most often precedes that of the cortex by several minutes, whereas reactivation of both structures during awakening is synchronized. Delays between thalamus and cortex deactivations can vary from one subject to another when a similar cortical region is considered.

Human thalamic and cortical activities assessed by dimension of activation and spectral edge frequency during sleep wake cycles.

Study Objectives: Using spectral edge frequency (SEF95) and dimension of activation (DA), a new tool derived from the dimension of correlation, we assessed the activation of thalamus and cortex in the different vigilance states.

Patients: Results were gathered from intracerebral recordings performed in 12 drug-resistant epileptic patients during video-stereoelectroencephalographic (SEEG) monitoring.

Results: In the cortex, we observed a progressive decrease of DA from wake to sleep, with minimal DA values characterizing the deep slow wave sleep (dSWS) stage.

[Contribution of non-linear mathematics (chaos theory) to EEG analysis].

Since 1963, nonlinear dynamics or "chaos theory" were widely used in various area of physics. The first application to the analysis of the human electroencephalogram (EEG) was performed in 1985. A tutorial revue of some concepts of nonlinear dynamics is presented with the various results obtained since 1985.

3-D eye movement measurements on four Comex's divers using video CCD cameras, during high pressure diving.

Previous studies have shown the vulnerability of the vestibular system regarding barotraumatism (1) and deep diving may induce immediate neurological changes (2). These extreme conditions (high pressure, limited examination time, restricted space, hydrogen-oxygen mixture, communication difficulties etc.) require adapted technology and associated fast experimental procedure.