Bilateral lesions involving the medial aspect of the hemisphere may induce pure amnestic syndromes. Which neural elements have to be destroyed remains open to question: hippocampus, mamillary body, dorso-medial nucleus of the thalamus play probably a role at one point or another of the memory process. Lesions of the dorso-lateral part of the frontal lobe disturb the chronological order of memories. Il has been suggested that 2 systems were involved: the first one is hippocampo-mamillo-thalamic (Papez circuit), the second one is amygdalo-thalamo-frontal. The respective role of each of these circuits remain controversial.