Do your memories disappear when you sleep?

by Kaitlin | March 8, 2007 at 03:28 pm

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This article--which I had to read a few times to get to the heart of, thanks to the folks at Scientific American (more power to you for not playing dumb)--basically breaks down to this: they thought that our brains stored memories by "using a 'sketch pad'" to record the information and experiences we encounter on a daily basis. This study, however, posits that we actually temporarily store these things in one part of our brains until we sleep, and then that information moves to a more permanent resting place, making room for new info the next day. Neato!

During sleep, instead of replaying a neuronal activity pattern of a learned behavior to the neocortex, the hippocampus responds to activity in the neocortex. Mehta and his colleagues surmise, "that [the] synchronous activation of [the] hippocampus by the [neo]cortex erases whatever you have learned recently from hippocampus."

In other words, rather than memories being transferred to the neocortex during sleep, the authors speculate that memories are stored in both the neocortex and the hippocampus. Then, during sleep, the hippocampus, acting as a temporary storage system, is cleared for another day of learning, while the memories are retained in the neocortex, which provides permanent storage much like a computer hard disk.

Bruce McNaughton, director of the Division of Neural Systems, Memory and Aging at the University of Arizona, believes the new work adds another piece to the puzzle, but does not believe it is a breakthrough. "The bottom line here is that this is a very very complicated system," he says, adding that he expects it to take another 20 years before the science community fully understands exactly how memories are formed and stored. "One has to be very careful, in interpreting the results done under anesthesia," he warns, "because it's totally not the same brain."