International audience We have covered the general outlines of Jaques Lacan’s main positions on psychogenesis and organogenesis with the help of a number of texts by writers who have studied the same issues. Lacan progressively moved from a position in his early psychiatric texts which was adjacent to Jasper’s to a dismissal of psychogenesis and dualism, based on the trinarity of the structure of the chain of the signifiers and the articulation of its three categories, the Real, the Symbolic and the Imaginary. Lacan’s theses relate to the concept of « not all» and the concept of « subject’s constitutive rift». These two lacanian concepts, that lead to the departure of Lacan from the body-psyche dualism, are present in different periods of his teachings. In this article we refer to the concept of «semiotic reduction» as an application of our own devise with reference to Lacan’s teachings on psychogenesis and organogenesis and more specifically on how one could consider the ‘deficit of organic functions’ including those of the brain in terms of Lacan’s theory.