Memory discoveries

 

Memory: It’s All About Connections

When we learn something—even as simple as someone’s name—we form connections between neurons in the brain. These synapses create new circuits between nerve cells, essentially remapping the brain. The sheer number of possible connections gives the brain unfathomable flexibility—each of the brain’s 100 billion nerve cells can have 10,000 connections to other nerve cells.

Those synapses get stronger or weaker depending on how often we’re exposed to an event. The more we’re exposed to an activity (like a golfer practicing a swing thousands of times) the stronger the connections. The less exposure, however, the weaker the connection, which is why it’s so hard to remember things like people’s names after the first introduction.

“What we’ve been trying to figure out is how does this occur, and how do you strengthen synapses at a molecular level?” Huganir says.

New Discoveries in Memory

Many of the research questions surrounding memory may have answers in complex interactions between certain brain chemicals—particularly glutamate—and neuronal receptors, which play a crucial role in the signaling between brain cells. Huganir and his team discovered that when mice are exposed to traumatic events, the level of neuronal receptors for glutamate increases at synapses in the amygdala, the fear center of the brain, and encodes the fear associated with the memory. Removing those receptors, however, reduces the strength of these connections, essentially erasing the fear component of the trauma but leaving the memory.

Now Huganir and his lab are developing drugs that target those receptors. The hope is that inactivating the receptors could help people with post-traumatic stress syndrome by reducing the fear associated with a traumatic memory, while strengthening them could improve learning, particularly in people with cognitive dysfunction or Alzheimer’s disease.