Perfect Memory? Forget About It

Medically Reviewed by Jacqueline Brooks, MBBCH, MRCPsych
From the WebMD Archives

March 15, 2001 -- "Ah, yes! I remember it well." You may think you remember it well, but as the old Jay Lerner song so aptly points out, you may be fooling yourself. Two people may have totally different recall of the same event, even if they are lovers reminiscing about their first meeting.

Which is not such a bad thing, according to recent research.

"It is often not necessary for us to be able to remember everything we said, thought, or experienced," psychologist Ulrich Hoffrage, PhD, tells WebMD. "It is often even good to forget in order not to overload our memories with garbage that we will never need any more."

With his colleagues at the Max Planck Institute for Human Development in Berlin, Germany, Hoffrage studied hindsight bias -- that phenomenon that makes us so good at Monday morning quarterbacking. The results were published last year by the American Psychological Association.

Hoffrage's group gave students nutrition information about different foods, asked them questions about that information, and asked them to recall their previous answers a day or a week later. Those students receiving no additional feedback had no change in their memory of their previous answers. But those students reminded of the nutritional information changed the memory of their earlier answers, correcting them to reflect the additional feedback.

Accurate memory of yesterday's beliefs is less important than updating beliefs to reflect new information, Hoffrage explains. "A gap in memory is often not a bad thing, since it often can be compensated for by reconstruction," he says.

How can the brain "reconstruct" old memories?

In research published last August in the journal Science, Karim Nader, PhD, and colleagues at New York University (NYU) in New York City found that stored memories are not all carved in stone. Frightening memories, at least, can be scattered like dust in the wind.

"Memories being remembered go back into a transient, unstable state," he tells WebMD. "From there, the memory can be stored again, or it can be inactivated." Nader is an assistant professor at NYU.

Nader's group studied rats trained to remember that a warning tone led to a painful foot shock. Ordinarily, sounding the tone made these rats freeze in fear even when the shock was not applied. If they were given a drug that blocked protein synthesis, they played happily when the tone went off.

Even more surprising, this lack of conditioned fear response persisted for periods of up to two weeks. By preventing protein synthesis needed for memory storage, the researchers had wiped out the painful memory.

"We don't yet understand completely which memories can be blocked," Nader says. "Content, fear or other emotion evoked by the memory, how long ago it was stored, or other factors may play a role."

Nader's research might ultimately benefit Vietnam War veterans suffering from post-traumatic stress disorder. If a veteran experiences "shell-shock" whenever he hears a loud noise that reminds him of a grenade exploding, giving him a drug that blocks memory storage while exposing him to an explosive sound might cure the problem.

But what if you want to remember, not to forget? How we successfully retrieve stored memories is the research focus of David I. Donaldson, PhD, a psychologist at Washington University in St. Louis.

"Neuroimaging techniques that allow us to see the workings of the brain are beginning to reveal the network of brain regions that are involved when people remember," Donaldson tells WebMD about research he published in the January and February issues of Neuroimage. "Several brain regions become more active when retrieval is successful than when no information can be remembered."

Episodic memory, or memory of personal events such as weddings, birthdays, or even everyday happenings, can be easily disrupted. "In the case of Alzheimer's disease this can become so severe that eventually an individual may not recognize his own family members," Donaldson says.

While there may be no immediate applications to Alzheimer's disease or other memory disorders, understanding the different brain regions and processes involved in trying to remember and in successfully remembering stored information may ultimately pay off.

"Whether this turns out to be help that comes in the form of medicine, mental training, or a combination of the two remains to be seen," Donaldson says.

By studying bilingual immigrants, Robert W. Schrauf, PhD, has shed new light on autobiographical memory for life events, which normally accumulates steadily over the lifespan and shows little disruption with normal aging. His findings are published in the December issue of Culture and Psychology.

Bilingual immigrants tend to remember events that took place in their homeland in their mother tongue, while they remember more recent events in their second language, according to Schrauf, a psychological anthropologist at the Buehler Center on Aging at Northwestern University Medical School in Chicago.

In Alzheimer's disease, blurring of episodic memory for past events may relate to difficulty in searching through memory rather than loss of the memories themselves, Schrauf explains.

"We are exploring how remembering in the mother tongue will help 'jump start' memories for bilingual immigrants with Alzheimer's disease," Schrauf says. "As clues to the past are made more detailed, more remembering will result."

As scientists tackle the problem of Alzheimer's disease and other memory disorders, episodic memory may be a good place to start.

"Impairment in episodic memory is frequently the first sign of developing dementia," says Endel Tulving, PhD, who holds a cognitive neuroscience chair at the Rotman Research Institute in Toronto. "Episodic memory has to do with remembering the 'what? where? when?' of experienced events. Our ability to detect the onset of dementia would be enhanced if all these components were taken into account."

Through studies using special imaging techniques, Tulving is exploring brain regions involved in episodic memory processes. The implications of understanding this form of memory may reach far beyond its applications to Alzheimer's disease.

Tulving believes that experiencing events as part of our past is based on self-awareness across time, allowing us to form future goals and to shape our behavior to achieve them.

Episodic memory allows us to think about the future and thereby helps human culture and civilization to evolve, he said at last year's meeting of the American Association for the Advancement of Science.

"It's a poor sort of memory that only works backwards," the Queen remarked to Alice in Lewis Carroll's Through the Looking Glass.

And Tulving might agree.