LTP: Memory, arousal, neither, both

Abstract

The neurophysiological phenomenon of LTP (long term potentiation) is considered by many to represent an adequate mechanism for acquiring or storing memories in the mammalian brain. In our target article, we reviewed the various arguments put forth in support of the LTP/memory hypothesis. We concluded that these arguments were inconsistent with the purported data base and proposed an alternative interpretation that we suggested was at least as compatible with the available data as the more widely held view. In doing so, we attempted to illustrate that the inadequacy of present experimental designs did not permit us to distinguish between equally viable hypotheses. In the four years since we wrote the first draft of our target article, hundreds of additional studies on LTP have been published and their results have been incorporated into current theories about memory. A diverse group of commentators responded to our target article with their own theories of how memories might be stored in the brain, some of which rely on LTP. Some commentators doubted whether memories can be stored through modifications of synaptic strength. Some assert that it will never be possible to understand the neural mechanisms of memory; still others remain hopeful that we will accomplish some semblance of a resolution, provided we appreciate LTP's role in a subset of seemingly amorphous memory systems. In summary, although it is commonly written that “LTP is a memory storage device,” the divergence of views among the commentators suggests, at least as strongly as our target article, that such conviction is unwarranted and fails to acknowledge both the lack of consensus regarding the role of LTP in memory and the complexity of the phenomenon of memory itself.