Two main questions drive scientists’ quest in understanding how memory get formed and stored in the brain: how does learning occur? And how does memory last for several years or even a life-time?

In the 1970s’, scientists proposed an artificial model, the Long Term Potentiation, that would mimic the brain plasticity, its capacity to reorganize after new experiences. They realized that an electrical shock induced in a rabbit’s hippocampus last for just a second, but gave a long term change in the brain: the connections between the neurons got stronger. But is LTP really important, or are scientists just fooling themselves? Even though it is a very artificial thing, it is hoped that by studying it, it could reveal the mechanism of memory storage.

Today, scientists are not sure yet that LTP is what happens when a memory is formed, but it has the properties everyone expect memory to have: it is triggered by a lot of electrical activity, which happens during learning, and the consequences of that is a persistent strengthening.

Sam Cooke took over Whitlock’s work at the Picower Institute. “Jonathan Whitlock’s study was important because he showed that LTP occurs when learning occurs. But he didn’t show that this was necessary or sufficient for information to be stored in the brain,” Cooke says. And that’s what Cooke aims at.

The first step to show that LTP is necessary to form memory is to try to erase memory. Scientists know that during the critical period of around half an hour after LTP is induced, its effect can be reversed. So if LTP is a key mechanism in information storage then, Cooke should be able to form a memory, and use another artificial process, the Long Term Depotentiation (LTD), to erase that memory. “In simple terms, LTP and LTD are just the opposite process,” Cooke adds.

To do so, Cooke trains animals and observes the changes in the connections between the neurons in their hippocampus. To record the changes, he implants 16 tiny electrodes in a rat hippocampus, which is not bigger than 2 mm deep and 6 mm long. Once equipped, the rat explores objects made out of LEGO with different textures on them. He learns what this objects he has never seen look like, and smell like. Then, Cooke removes one of the objects and replaces it with a new object. The fact that the rat doesn’t explore a familiar object demonstrates that he remembers it. “The rat is just interested in new things he’s never seen before,” Cooke says. At that point, he knows a memory has been formed.

To erase it, he applies a low-frequency stimulation into the rat hippocampus. In doing so, Cooke hopes to mismatch, or disassociate the connections between the neurons involved in that specific memory the rat has just formed. As fast as two fingers clapping, the memory could be erased. But Cooke is only at the beginning of his study and hasn’t published any peer-reviewed article yet. More reserved than Whitlock, he knows his research requires a long set of experiments before he can tell any definitive result about his work.

Scientists know from experiments made in the 1950’s that the hippocampus plays a role in memory formation. Listen to Cooke’s thoughts on that bean-shaped part of the brain.