Puzzling thoughts for H.M.: Can new semantic information be anchored to old semantic memories? Neuropsychology 2004

Researchers currently debate whether new semantic knowledge can be learned and retrieved despite extensive damage to medial temporal lobe (MTL) structures. The authors explored whether H.M., a patient with amnesia, could acquire new semantic information in the context of his lifelong hobby of solving crossword puzzles. First, H.M. was tested on a series of word-skills tests believed important in solving crosswords. He also completed 3 new crosswords: 1 puzzle testing pre-1953 knowledge, another testing post-1953 knowledge, and another combining the 2 by giving postoperative semantic clues for preoperative answers. From the results, the authors concluded that H.M. can acquire new semantic knowledge, at least temporarily, when he can anchor it to mental representations established preoperatively. Memory is not a unitary capacity but, instead, can be divided into anatomically and functionally independent systems. Promi-nent among these divisions is the distinction between declarative (explicit) memory, the conscious recollection of facts and past events, and nondeclarative (implicit) memory, the influence of previous experience on task performance without conscious refer