11/01/1995 08:00:00

Question of the month: How do we remember?

Answered by Erin Schuman, Assistant Professor of Biology, Caltech

Question: What happens to your brain when you remember something?

When you remember something, there are a couple of ideas about what happens in your brain. Both involve improving the communication between neurons.

One idea is that certain synapses—the links between neurons—are strengthened, which improves the interaction between neurons. One scientific term for this strengthening is long-term potentiation, or LTP for short. In essence, LTP says that if two neurons are active at the same time, then the synapse between them will tend to be strengthened.

The other theory about how communication between neurons improves says that the properties of the individual neurons change, rather than the synapses between them. The result, enhancing the flow of information through the network of neurons, is the same for both theories, and both are widely accepted.

Memory formation via LTP involves many biochemical steps. The entire process is very complicated and is not fully understood, but scientists have identified a few of the molecules that are involved. One is nitric oxide (NO)—not to be confused with laughing gas, or nitrous oxide (N2O). Other molecules that most scientists agree play a role in LTP are NMDA receptors and protein kinases. Two more molecules whose involvement in LTP was discovered recently in my lab are named BDNF and NT-3. Both are neurotrophic factors, named for their role in keeping nerve cells healthy. They may actually represent a distinct way in which synapses enhance their strength.

If we can identify all the molecules involved and understand how they interact to create changes in synaptic strength, then eventually we might discern the differences between people with sharp memories and those who are more forgetful. This research may also one day shed light on how memory is affected by such things as age, nutrition, disease, and paying attention. And as the ultimate, far-in-the-future goal, this knowledge might enable doctors to slow the normal biochemical changes in the brain that come with aging, or to supplement memory molecules that are in short supply in the brain.

This is a monthly feature produced by the Media Relations Office at the California Institute of Technology, in collaboration with Caltech's faculty, to answer commonly asked or particularly intriguing questions about science and the natural world. The Media Relations Office invites your science questions.

Contact: Jay Aller (818) 395-3631 aller@caltech.edu

Written by John Avery