For some neurobiologists, present biological descriptions of the brain may integrate the theoretical frame initiated by Freud. The recent acquisitions of neurobiology prove a plasticity of the neural network anabling the inscription of the experiment. The neuroplasticity constitutes the cornerstone of the reconciliation between the psychoanalysis and neurosciences. The brain must not be considered as a rigid organ, determined and determining but well as a dynamic structure, in constant rebuilding. Contrary to the genetic determinism, the plasticity involves diversity and singularity. The variations of the feasible offered by the plasticity are seducing but to what extent towards the constraint of genetics and the epigenetic ? Both concepts, plasticity and epigenesis are well distinct. An epigenetic phenomenon associated to a maternal behaviour seems to have been proved recently in the rat. Attachment and depression require reflection in the sight of epigenesis and plasticity. The Freud concepts are not always applied to biological patterns without any clumsiness. Demonstrating psychoanalysis from neurosciences or the contrary does not seem very realistic. On the other hand there should a good reason to give rise to exchange, to make a clear distinction between psychoanalytical unconsciousness and neurological unconsciousness, and put an end to the groundless opposition between mental and cerebral.