1966

Long-term potentiation

Terje Lømo first observes long-lasting synaptic potentiation

Lømo was not looking for a memory mechanism. The strengthened response in a rabbit's hippocampus simply refused to fade.

An accident in Per Andersen's laboratory

In 1966, beginning independent doctoral work in Per Andersen's University of Oslo laboratory, Terje Lømo stimulated the perforant-path input to dentate granule cells in anesthetized rabbits. His project concerned that pathway, dentate physiology and the already-described phenomenon of frequency potentiation.

Testing responses at longer intervals after stimulus trains, he found something he had not gone looking for: brief trains increased the efficiency of transmission at perforant-path–granule-cell synapses, and the enhancement could persist for hours.

No exact calendar day for the observation is established in the consulted histories; only the year is securely supported.

An abstract nobody noticed

Lømo reported the preliminary finding in a 1966 abstract and a short presentation to the Scandinavian Physiological Society in Turku, suggesting the effect might represent a form of synaptic memory.

It attracted little attention and was not immediately pursued. The experiments later failed in the same Oslo laboratory and preparation, which helps explain the delay.

Timothy Bliss arrived in Oslo in 1968 and persuaded Lømo to run the systematic experiments; they were performed in 1968–1969 and published in 1973.

What the observation was not

It was an observation and a brief abstract, not the canonical full paper — seven years separate the two.

Lømo recorded extracellular population responses from dentate granule cells, not the behaviour of a single isolated postsynaptic neuron.

The name came afterwards. "Long-term potentiation" was applied retrospectively, and firsthand histories dispute any single clean naming moment.

Sources

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What the sources leave uncertain

No exact calendar day for the laboratory observation is established in the consulted histories; only the year 1966 is securely supported.
“First observed” must be distinguished from the first full description. The preliminary observation and abstract date to 1966, while the canonical Bliss–Lømo paper appeared in 1973.
The label LTP was applied retrospectively. Lømo’s observation predated stabilization of the name “long-term potentiation.”