Memories Have Time Stamps

via CNN

What was the name of that guy with that stuff in that place with those things? Don’t you remember?

We all suffer occasional lapses in memory. Some people suffer severe neurological conditions, such as Alzheimer’s, that rob them of their ability to form memories or remember recent events.

Three new studies shed light on the way the brain forms, stores and retrieves memories. Experts say they could have implications for people with certain mental disorders.

Newly born brain cells, thousands of which are generated each day, help “time stamp” memories, according to a computer simulation by scientists at the Salk Institute for Biological Studies in La Jolla, California, and the University of Queensland in Australia. The research was published in the journal Neuron.

These cells do not record an exact, absolute date — such as January 28, 2009 — but instead encode memories that occur around the same time similarly. In this way, the mind knows whether a memory happened before, after or alongside something else.

Neuroscientists believe that if the same neurons are active during two events, a memory linking the two may be formed.

For example, you might remember that, on a day a few years ago, you went to a restaurant and then went to a baseball game. Researchers think the same neurons are active during both events, which results in an association with each other when you remember them.

In fact, the same young neurons respond to everything that happens for several weeks, said two of the study’s co-authors, professor Fred Gage and graduate student Brad Aimone from the Salk Institute. While associations are known to form based on sight, smell, and other senses — you may remember last year’s baseball game through the taste of a hot dog today, for example — their computer model shows that the young brain cells also link through time.

“Even though these young cells are only a small percentage of the overall circuit, we believe that their effect may be enough to give people the sense of “this happened around the same time as” something else, Gage and Aimone wrote in an e-mail.

The findings could have promising implications for diseases that involve a neurogenesis deficit — in other words, a lack of new brain cells being born — which happens in conditions such as depression, Alzheimer’s and Parkinson’s, the authors said.