Probing the Mechanics Behind How We Remember

At the chemical level, memory storage seems to activate the nerve cell to start a cascade of reactions that can last a fraction of a second or linger for years, depending on the type of memory being stored. While much of this work has been conducted in sea snails, there's evidence to suggest that the process applies to higher species, including people.

Alkon and his colleagues at the National Institute of Neurological Disorders and Stroke have found that the first change is in calcium, which floods into the neuron within milliseconds of the start of a memory task. This is one of the things that scientists believe happens when you look up a phone number for a restaurant and hold it in memory for just the short time it takes to place the call.

This ability "is what people refer to as working memory," said Robert Desimone, director of NIMH's Intramural Research Program.

But if you need to remember that phone number permanently, rehearsal is necessary, and it prompts an intricate series of reactions within the nerve cell.

Acuity of Interest Can Affect Retention

Why some memories are saved and others are simply discarded in healthy people appears to be determined in part by attention. Throughout the day, the brain is bombarded by thousands of pieces of information. Remembering every activity of every day would quickly overload neural circuits.

So the novelty of certain situations and the emotions and other sensory cues about them help dictate their importance and their storage in our memories. Vivid, emotional experiences appear to release chemicals in the brain that aid in the storage of information, Desimone said. "So, if I tell you, 'I'm going to give you this Pizza Hut number and I want you to remember it,' you probably would for a few minutes. But if I said, 'Remember this number, or I will kill you,' it might actually get stored right away in your long-term memory."

Attention, whether prompted by fear or genuine interest, helps filter what is saved in memory, and for this reason, it has become one of the new frontiers in memory research.

As the population ages, understanding memory is vital for battling Alzheimer's disease and other age-related dementias. But it's not just the elderly who can benefit from memory research.

Only by understanding how memory works can researchers open the door to new treatments for psychiatric illnesses and learning disabilities.

"Memory is the most significant of all the mental processes," Kandel said. "Memory is involved in every aspect of our lives."