[Evoked potentials and structured and colored stimuli].

After a historical account and a brief description of the techniques of signal analysis used in their laboratory (visual evoked potentials (VEPs) with statistical calculations, Fast Fourier Transform, correlation function), the authors present the experiments they undertook concerning colored stimulations. These experiments were carried out in 3 steps: colored stimulations on a cathode-ray screen, with constant luminance, concerning 8 healthy volunteers (72 VEPs analyzed); colored stimulations on a 'structured' screen (pattern reversal), concerning 31 healthy volunteers (186 VEPs analyzed); colored and pattern stimulations on a new cathode-ray stimulator built in the 'Centre National des Arts et Métiers' enabling both preceding types of stimulations with increased reliability and offering new possibilities of stimulation (variation of contrast, luminance or chromaticity precisely controlled) with various patterns in the background. The results evidence two different groups of electrophysiological responses, distinctly related to the presence or absence of a morphological structure in the stimulation.

Status of vestibular function after prolonged bedrest.

6 young, healthy, male volunteers were submitted to one week of head down (-4 degrees) bedrest. This position simulates the cerebral hemodynamic conditions in weightlessness. Measurements of vestibular equilibrium and of oculomotor system function were made before and after the prolonged bedrest.