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Karim Benchenane’s article, the third contribution to our dossier on brain plasticity, revisits this notion to explain that it covers “the way experience will, in the long term, modify the effectiveness with which neurons are able to communicate among themselves.” Though he stresses the primordial role of the earliest years, he nonetheless observes that, contrary to what we had long thought, this plasticity lasts a whole lifetime. Benchenane then explains the mechanisms governing memory, while stressing that there are different forms — most notably, short-term and long-term memory — not all of them dependent on the hippocampus. Then, as learning and memorization consume a large part of the energy required for brain functioning, he reminds us of the importance of sleep, which is required for physical recovery. He is careful also to underscore that these processes are still subjects of scientific controversy, which he lays out here very clearly and interestingly. Lastly, Benchenane alerts us to the risk of falling victim, as we sleep, to social conditioning and he closes his article with some thoughts on brain-machine interactions, a subject to which we shall return in our third dossier on the brain, to be published at the end of the year.