The present invention relates to the medical field, in particular to the enhancement of brain performances and for the treatment of pathological stress. More specifically the present invention relates to a nanoparticle or nanoparticles' aggregate for use in enhancing brain performances or in prevention or treatment of pathological stress in a subject without exposure of the nanoparticle or nanoparticles' aggregate to an electric field, and preferably without exposure thereof to any other external activation source, wherein the nanoparticle's or nanoparticles' aggregate's material is selected from a conductor material, a semiconductor material, an insulator material with a dielectric constant ε ijk equal to or above 200, and an insulator material with a dielectric constant ε ijk equal to or below 100. It further relates to compositions and kits comprising such nanoparticles and/or nanoparticles' aggregates as well as to uses thereof without exposure thereof to an electric field, and preferably without exposure thereof to any other external activation source such as a light source, a magnetic field, or an ultrasound source.