Uncovering amnesiacs' hidden memories.

Uncovering amnesiacs' hidden memories

University of Toronto researchers aretapping the unconscious memory systems of amnesia victims, enabling some patients to remember and learn certain facts for the first time since the onset of amnesia. The use of this "implicit memory' component now offers "some hope for teaching amnesiacs complex, new knowledge,' psychologist Daniel L. Schacter reported this week in Chicago at the American Association for the Advancement of Science annual meeting.

Working with victims of head injury,encephalitis, Alzheimer's disease and other physiological syndromes, Schacter and his colleagues tackled the problem of "antrograde amnesia,' in which people are unable to remember facts and events that have occurred since their injury or disease. Historically, he says, attempts to restore this type of memory to such people have been "useless.' Most of those efforts involved "explicit memory': asking the person to consciously recall a word, event or fact that was presented a short time earlier.

But some promising, isolated resultsover the past decade suggested that in the process of learning certain skills or tasks, some amnesia patients demonstrate that they do remember, even though, when asked, they cannot consciously recall what they had been taught. In a series of recent studies, Schacter has used this unconscious, implicit memory to teach computer vocabulary and programming skills to amnesiacs.

In his latest work with three head-injuryvictims and one encephalitis victim, the psychologist employed a technique called "the method of vanishing cues.' This involved "priming,' in which the patient was asked to identify a computer-related concept--for example, "a repeated portion of a program.' The patients were given the answer, "loop,' just once, and were subsequently given fewer and fewer letters of the word-- "loo-,' "lo--,' "l---'--until finally they were given no letters.

After eight trials, Schacter reports thatthere was "little or no forgetting after a six-week delay.' Moreover, the patients went on to be able to write computer programs, and had retained such information when tested months later.

"We've found that even severely amnesicpatients perform relatively well on implicit tests of memory,' he says. "They are not aware that they are remembering or learning, but we've been able to push the preserved and residual memory abilities that they do have.'

Because of their short-term memoryproblems, many amnesiacs have been unable to get jobs and lead relatively normal lives. The next logical question, Schacter says, was, "Is it possible to build on those [implicit memory] skills to help these people in their lives?'

Schacter and his colleagues then attemptedjob training with one of his four latest subjects--a woman with viral encephalitis. The job was a rather complicated process, involving transferring business information from a card onto an eight-column display; the woman had to learn to identify multidigit numbers and such terms as "Doc. #' (document number) and "Ser. #' (serial number).

Schacter again used the method ofvanishing cues. After an initially poor performance, the woman improved dramatically over the next several sessions and was completing transfers in 10 to 11 seconds, comparable to people already on the job. She accomplished this, he notes, even though "she did not recall the events of training explicitly.'

Among such amnesia victims, he adds,IQ, vocabulary and skills have not been impaired--it's simply a matter of enabling the people to use those skills once again. "What we've done so far,' he says, "is to shed light on some form of memory and to demonstrate that people with amnesia due to head injury [and other physiological causes] have the potential to perform useful tasks.'