Cognitive Syndromes
Learning Feasible After Memory Loss, Study Says
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A Washington State University neuropsychologist has demonstrated there is a way for severely brain-damaged patients to learn even though their memories are impaired.
In a series of complex computer tests, Maureen Schmitter-Edgecombe and her assistant, Heather M. Nissley, showed that patients with severe closed-head injuries could identify, recall and then indicate where on their computer screen a given "target number" had been flashed.
The study indicates that persons who have survived serious head injuries are able to learn "without awareness," as one critique puts it. That finding raises hope for lessening the disability of certain cognitively disabled victims through innovative rehabilitation techniques.
Beyond that, the study, which appears in the scholarly journal Neuropsychology, contributes to the gathering evidence that implicit learning is facilitated by a separate neural mechanism in the brain than explicit learning. It's thought that the separate system that evolved early in man's development is comparatively unchanging and tends to be more resilient than the system used in explicit learning.
"I don't want to go beyond the data, but we demonstrated - in what we believe is a perceptual, implicit system - that the closed-head-injury patients learn just like normal people, although they are not aware they are learning," says Mrs. Schmitter-Edgecombe.
By "implicit system," Mrs. Schmitter-Edgecombe refers to a learning process like that used by young children who learn rules of grammar and piece together coherent sentences without having to be taught how - and without realizing they are learning. Implicit learning is contrasted with "explicit learning," the kind of purposeful attention and memorization used in school or on the job.
"The key for us now is to figure out how to utilize these unconscious mechanisms that don't involve a conscious learning route. We now know the potential for learning exists. We have to find out how to work with that knowledge," she says.
Physicians and psychologists use the term "closed-head injury" to refer to a "traumatic brain injury" caused by an external physical force that slams the brain against the skull but does not cause the skull to break or be penetrated. Such injuries are fairly common.
Psychologists say they are probably more common than we know because many times the brain damage goes undiagnosed or is misdiagnosed.
The damage can be extensive. It affects the ability to think and can erase the capacity to remember events and even words. It can rob the victim of the ability to concentrate, learn, keep up in conversation or do more than one thing at a time. Aside from the cognitive consequences, behavior and emotional reactions can be altered by the injuries.
Automobile and motorcycle accidents are the chief cause of such injuries among adolescents and young adults, while falls mainly cause such injuries to persons over the age of 75. The Brain Injury Association, a patient advocacy and education organization, reports that 5.3 million Americans - 2 percent of the population - live with disabilities resulting from severe head injuries.
Some 1.5 million people sustain brain injuries each year. Roughly 80,000 of those victims experience long-term disability.
Mrs. Schmitter-Edgecombe's study explains the results of testing done on 19 victims, still disabled a year after their accidents, and 19 uninjured "control" subjects. The brain-injured subjects ranged in age from 15 to 55. All had been in a coma for at least 24 hours in the course of their recovery. Fifteen of the victims had been hurt in motor-vehicle crashes. Four were damaged when they fell from a height of more than 10 feet.
The control subjects were chosen to resemble the injured subjects in sex, age and other salient characteristics. When the test performances of the injured and uninjured were compared, it was shown that the disabled learned as well as the uninjured and healthy test subjects.
August Gribbin is a staff writer with the Washington Times.
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