This project proposes to investigate the impact of transcranial electrical stimulations (TES) on the human brain and more precisely on the visual ventral stream that supports vision and memory processes. In order to precisely validate the impact of TES, we will use simultaneous multi-scale electroencephalographic (EEG) recordings and fast periodic visual stimulations (FVPS). This coupling in human in-vivo is unique in worldwide. Multi-scale EEG recordings (intracerebral and scalp) is rare and allow the precise investigation of brain functioning from the neural populations to the surface of the scalp (Koessler et al., 2015; Jacques et al., 2019 & 2020). The FPVS is a robust, fast, specific method which allows to measure evoked potentials of the human brain in the frequency domain. In order to evaluate the impact of the TES, we will investigate both drug resistant epileptic patients and healthy subjects. We will analyze cognitive EEG biomarkers (evoked by the FPVS) in terms of amplitude, signal to noise ratio and anatomical distribution during three steps: before the TES, during the TES and after the TES. Finally, we will design and evaluate the abilities of a new FPVS-EEG system (Bioserenity®) to record these cognitive biomarkers in these clinical and experimental contexts.