LTP - MEMORY, AROUSAL, NEITHER, BOTH

The neurophysiological phenomenon of LTP (long term potentiation) is c onsidered by many to represent adn adequate mechanism for acquiring or storing memories in the mammalian brain. In our target article, we re viewed the various arguments put forth in support of the LTP/memory hy pothesis. We concluded that these arguments were inconsistent with the purported data base and proposed an alternative interpretation that w e suggested was at least as compatible with the available data as the more widely held view. In doing so, we attempted to illustrate that th e inadequacy of present experimental designs did not permit us to dist inguish between equally viable hypotheses. In the four years since we wrote the first draft of our target article, hundreds of additional st udies on LTP have been published and their results have been incorpora ted into current theories about memory. A diverse group of commentator s responded to our target article with their own theories of how memor ies might be stored in the brain, some of which rely on LTP. Some comm entators doubted whether memories can be stored through modifications of synaptic strength. Some assert that it will never be possible to un derstand the neural mechanisms of memory; still others remain hopeful that we will accomplish some semblance of a resolution, provided we ap preciate LTP's role in a subset of seemingly amorphous memory systems. In summary, although it is commonly written that ''LTP is a memory st orage device,'' the divergence of views among the commentators suggest s, at least as strongly as our target article, that such conviction is unwarranted and fails to acknowledge both the lack of consensus regar ding the role of LTP in memory and the complexity of the phenomenon of memory itself.