Healthy participants aged from 1 to 75 years old. All experiments conducted in this study will make use of the electroencephalogram (EEG) recording technique. Healthy participants cannot participate if they suffer from dermatosis on the scalp. There is no other contraindication to the practice of an EEG, which simply consists of recording the electrical activity of the brain on a trace, after application of a conductive gel on the scalp where sensors connected to a recording device are placed.

We will collect the cerebral electrical response by the technique of steady state visual evoked potentials (SSVEP) which consists of presenting a visual stimulus periodically to interpret the EEG signal according to those variations.

Electroencephalography is registered through a 68-electrode electroencephalography while stimuli will be presented at the centre of the screen at a distance of 150cm.

The pattern of visual stimulation is based on the technique of steady state visual evoked potentials. These potentials consist of the presentation of a visual stimulus at a (relatively fast) periodic rate to produce an EEG signal over the occipital cortex exactly at the frequency of stimulation. By varying the value of a parameter of the stimulation (e.g. the contrast of the stimulus) varies. This variation makes it possible to determine the threshold value where an EEG response is perceived, and thus to evaluate visual parameters such as visual acuity, contrast sensitivity or recognition of more complex shapes.

Fast periodic visual stimulation using stimuli such as gratings, checkerboards, words and faces