 The usual evidence marshaled in favor of C1 relies on amnesiac case studies (Milner 1962; see Cohen &amp; Squire 1980 for discussion). A typical example is HM. After bilateral removal of the hippocampus, parahippocampal gyrus, entorhinal cortex, and most of the amygdala to relieve debilitating symptoms of epilepsy, HM was unable to form new memories of facts or events and he could no longer access memories he acquired in the few years leading up to his surgery. Nevertheless, it was found that over 10 trials, HM tuned his motor skill to trace the outline of a five-pointed star based only on looking at reflection in a mirror. Since he could not store new memories, HM’s declarative knowledge of the means of performing the task did not change from one trial to the next. But his performance improved. So, the reasoning goes, the improvement of motor skills is governed by a distinct cognitive system from that which governs the retention of declarative facts.