Introduction
From time to time, someone asks, “why do we call it LTP?” referring to “long-term potentiation (LTP)” as the name for the persistent increase in synaptic strength that occurs in many brain areas. A few opinions and anecdotes have been put forward. The history of the name “LTP” is not extremely important in the grand scheme of neuroscience. Nevertheless, if it’s important enough to mention at all, then it’s important enough to get straight. Here is the true story of the name “LTP,” i.e., the one that is verifiable by anyone who wishes to check it. The reality is that LTP was named by Alger and Teyler in 1976.
In 1966 in Per Andersen’s lab in Oslo, Terje Lomo found that transiently raising the stimulation frequency of hippocampal axons caused a marked and prolonged increase in the ability of those axons to induce a postsynaptic response. In 1973, Timothy Bliss and Lomo followed up and published their famous paper entitled, “Long-lasting potentiation of synaptic transmission in the dentate area of the anaesthetized rabbit following stimulation of the perforant path.”
Descriptions are not names
You might think their name for the phenomenon was “long-lasting potentiation.” But this is not true. First, neither Bliss nor Lomo ever claimed it was. Second, in the text of their paper, they refer to the phenomenon variably as “long-lasting potentiation” or “long-term potentiation.” Clearly, the designations “long-lasting” and “long-term” were descriptions, not names.
The distinction between “description” and “name” is critical to sorting out the whole issue, so let’s consider it briefly. A name is a unique tag that we apply to something. The name identifies that thing and we use the name consistently. If you name your dog, Fido, then that’s his name and you always call him Fido when his food is ready, for instance. You do not name him “Fido” and also sometimes call him “Spot” of “Mopsy.” However, you can refer to Fido by different descriptions, and descriptions vary according to circumstances. You might refer to Fido as “my furry little friend,” or “the guard dog,” or “stinky,” without implying that that’s his name.
Did Douglas and Goddard name it?
It is sometimes said that Douglas and Goddard named the phenomenon by titling their paper, “Long-term potentiation of the perforant path-granule cell synapse in the rat hippocampus” (Brain Res, 1975). An examination of the document as well as the subsequent publications of the Goddard lab indicates otherwise. First, the phrase “long-term potentiation” only occurs in the title of their paper and nowhere else; not the Abstract, Results, Figures, or Discussion. The text refers to “the potentiation,” 33 times, with the qualifiers “post-tetanic,” or “long lasting” another 5 times, but not once to “long-term potentiation.” If the name was “long-term potentiation” why not use it? Second, their next paper on the topic, (McNaughton, Douglas, and Goddard; Brain Res, 1978) explicitly named the phenomenon, “long-term enhancement.” Clearly, the Goddard lab did not consider “long-term potentiation” to be a name. Third, a prominent graduate of the Goddard laboratory, Bruce McNaughton, continued to study “long-term enhancement,” which he abbreviated “LTE,” throughout the 1980s and early 1990s. Fourth, LTE and LTP are identical. Evidence for this claim is that, later McNaughton papers transitioned into calling “LTE/LTP.”
In summary, the objective evidence contradicts the claim that the Goddard lab named the phenomenon, “long-term potentiation.” Likewise, in September 1976, Gary Lynch’s lab mentioned “Long term potentiation” only in their Nature paper title, not in the text, and not as a name. In all these cases, “long-term,” appeared as a description, not as part of a name.
The origin of long-term potentiation (LTP) as the name
In the 1972, Timothy Teyler returned from a sabbatical in Oslo where he had learned the hippocampal slice technique and observed Lomo’s phenomenon. At the time the Andersen lab referred to it simply as “plasticity” (e.g., Bliss and Lomo, 1970). Adding to the confusion, in 1975 Schwartzkroin and Wester’s paper on the potentiation called it “long-lasting facilitation.” Obviously, things were getting nowhere when it came to the name. Teyler and I were in the Department of Psychology at Harvard when we finished our first paper on synaptic plasticity and wanted a real name for the long-term phenomenon. In those days psychology divided memory mainly into “long-term” and “short-term” memory which, in textbooks, were designated “LTM” and “STM.” Since people already considered long-term potentiation to be a likely substrate for LTM, making the name explicit and abbreviating it “LTP” was a natural step, so we took it. We used the name “long-term potentiation” and “LTP” consistently in our paper in 1976. Its true that the three letters do fall “trippingly from the tongue,” as has been pointed out, but that’s not why Teyler and I chose them.
And that’s why we call it LTP.
References
Alger BE, Teyler TJ (1976) Long-term and short-term plasticity in the CA1, CA3, and dentate regions of the rat hippocampal slice. Brain Res,110(3):463-80.
Bliss TV, Lomo T (1970) Plasticity in a monosynaptic cortical pathway. J Physiol, 207(2):61P.
Bliss TV, Lomo T(1973) Long-lasting potentiation of synaptic transmission in the dentate area of the anaesthetized rabbit following stimulation of the perforant path. J Physiol, 232(2):331-56.
Douglas RM, Goddard GV (1975) Long-term potentiation of the perforant path-granule cell synapse in the rat hippocampus. Brain Res, 86(2):205-15.
Lynch GS, Gribkoff VK, Deadwyler SA (1976) Long term potentiation is accompanied by a reduction in dendritic responsiveness to glutamic acid. Nature, 263(5573):151-3
Lømo T (1966). “Frequency potentiation of excitatory synaptic activity in the dentate area of the hippocampal formation”. Acta Physiologica Scandinavica. 68 (Suppl 277): 128.
McNaughton BL, Douglas RM, Goddard GV (1978) Synaptic enhancement in fascia dentata: cooperativity among coactive afferents. Brain Res, 157(2):277-93.
Schwartzkroin PA, Wester K (1975) Long-lasting facilitation of a synaptic potential following tetanization in the in vitro hippocampal slice. Brain Res, 89(1):107-19.