The Molecule of the Memory

Scientists have been looking for long time for a memory molecule.

By now, a European team has found one in mice's hipocampus (a brain area linked to the many functions), connected to their ability to learn, form memories and recall them.

"Obviously, mental illnesses can better be cured when you know what molecules are involved. Right now, these drugs in existence, they do something, but very little. And I think that is because of a lack of knowledge about the molecular mechanism. It is not the first target to make a drug, but (our discovery) definitely will aid the people that do that work," said Liliana Minichiello at the European Molecular Biology Laboratory in Monterotondo, Italy.

Brain cells communicate via electrical signals and a particularly strong and long-lasting signal to a brain cell is thought to point the formation of a new memory or long-term protentation (LTP).

LTP is the origin of learning and recalling at the molecular level. That's why scientists monitored the brain while learning. Thus, the Italian-Spanish team monitored mice while they learned and recalled that new knowledge. This way they could check the role of a receptor molecule called TrkB, found in some hippocampus cells, for the LTP process.

"Other studies in our lab said that this molecule was significant. This went deeper and produced more evidence. We measured the LTP while the mouse was conscious and learning. The mouse was alive," Minichiello said.

The researchers found that mice with mutated/defective TrkB molecules could not activate an important signaling pathway, and were also unable to learn. Moreover, the cells with defective TrkB molecules could not generate a normal LTP recall response (remembering) when presented with a familiar situation. Thus, healthy TrkB molecules were strongly associated with the ability to learn and recall something that had been memorized. "We established that while the mouse is learning, there are changes in the hippocampus that do not happen if you mutate the receptor. It helps us to understand the molecular pathway for learning, but also for generating LTP," Minichiello said.

"The discovery is significant in that it is the first time scientists have been able to prove that TrkB and the signaling pathway it activates are essential to learning and memory," said Minichiello.