Soman, an anticholinesterasic neurotoxic drug, induces epileptic seizures during severe intoxication. Their trigger conditions still remain unknown and a great variability between animals is observed. The butterfly model in the catastrophe theory has been used to explain these triggering conditions.We have developed a technique allowing, in freely moving rats, the « in vivo » determination of three sets of neurophysiological data, followed before and during a soman intoxication. For the same rat, we associated cortical acetylcholinesterase (AChE) activity by microdialysis with (...) both the assay of extracellular acetylcholine (ACh) concentrations and electroencephalographic (EEG) recording and power spectrum analysis (gamma band). Data have been analysed to define the critical parameters which lead to the epileptic fit. (shrink)

High noise levels may have an adverse effect on the normal cochlea function and lead to significant hearing loss. Clinically, exposure to high intensity impulse noise produces a wide range of audiometric effects which may result in long term or even irreversible symptoms. Nevertheless, there is sometimes a spontaneous rebound recovery of the auditory function. This phenomenon was previously studied in the vision, another sensory function. It was called the visual survival attractor.In view of the importance that the sensory organs (...) have for the brain, and in particular in its function of recognising and dealing with its environment, it was interesting to know whether this survival attractor concept already described for vision occurs more generally in all the sensory functions. With this in mind we present here the results of a new study, this time on hearing. (shrink)

This work is a qualitative study of an organism''s physiological adaptative response to stress. The experimental data were selected from a previous study leading to the conclusion that stress may be considered as a topological retraction within a vital space that must be more precisely defined. The experimental methodology uses rat poisoning by neurotoxins. The control parameter is the intensity of the toxic doses. Measured parameters are the animals'' survival rate and the kinetics of cerebral acetylcholinesterase activity. The results, when (...) expressed as a function of the inverted doses, show a characteristic evolution. The pattern of the curve closely resembles a vortex profile. This analogy is studied more extensively in both the physical and biological domains. These findings help to clarify the concept of biological stress which presents the same vectorial properties as hydrodynamic vorticity. In particular, the dissipation of stress and the dissipation of vorticity seem to obey the same laws. This observation is valid for both diffusion and convection processes. The decompensation phase of stress could be compared with the instability and turbulence in flows.Our approach in this paper is mainly to establish a general and phenomenological description of the stress response fitting experimental observations. (shrink)