[Remembering an amnesic patient (and half a century of memory research)].

The development of memory research is inextricably bound to the fate of patient HM. On the occasion of his death, the circumstances are remembered, which lead to the bilateral removal of parts of his medio-temporal cortex in 1953. And the importance of the subsequent more than a half-century of research about his postoperative amnesic deficits as well as remaining learning and memory functions are outlined. The early reports triggered improved animal research which together with parallel investigations on HM and patients with similar deficits eventually lead to the downfall of the up until then dominating antilocalisationist view of brain functions. This was the result of having convincingly shown that memory could be severely impaired without major changes in other cognitive functions. Later investigations lead to question the unity of memory itself and forced a more and more differentiated description of different kinds of memory and their associations with separate neuroanatomical structures. A simplified summary of the resulting recent ideas of declarative memory systems is presented together with an outline of connections to their supporting medio-temporal, diencephalic and frontal-cortical structures. Finally, an attempt is made to address the question about the impact on the person HM of not having been able to form consciously retrievable memories from age 27 until his death at age of 82, thus having to rely for a reconstruction of his life on memories from child- and young adulthood as well as single momentary short-lived experiences.