Human memory has historically defied precise scientific description, its biological functions broadly but imperfectly defined in psychological terms. In a pair of papers published in the Nov. 2 issue of The Journal of Neuroscience, researchers at the University of California, San Diego report a new methodology（方法学） that more deeply parses how and where certain types of memories are processed in the brain, and challenges earlier assumptions about the role of the hippocampus（海马） . Specifically, Larry R. Squire, PhD, a Research Career scientist at the VA Medical Center, San Diego and professor of psychiatry, neurosciences, and psychology at UC San Diego, and Christine N. Smith, PhD, a project scientist, say that contrary to current thinking the hippocampus (a small seahorse-shaped structure located deep in the center of the brain and long associated with memory function) supports both recollection and familiarity（熟悉，精通） memories when these memories are strong.

Recollection and familiarity memory are two components of recognition memory -- the ability to identify an item as having been previously encountered. Recollection memory involves remembering specific details about a learning episode, such as where and when the episode occurred. Familiarity memory refers to remembering an item as previously encountered, but without any recall of specific details, such as recognizing someone's face but recalling nothing else about that person (For example, where you met the person.).

Prevailing（流行的，一般的） research posits that recollection and familiarity memories involve different regions in the brain's medial temporal lobe: the hippocampus for recollection, the adjacent perirhinal cortex for familiarity.

"But given the connectivity in that part of the human brain, that separation seemed too clean, too neat," said Squire, a leading expert on the neurological bases of memory. "The idea of distinct functions was unlikely."

Recollection-based memories are typically associated with higher confidence and accuracy than familiarity-based decisions. Accordingly, in the past, comparisons between recollection and familiarity have also involved a comparison between strong memories and weak memories. So the question is how the brain accomplishes recollection and familiarity when the effect of memory strength is taken off the table.