The patients that DeLuca works with confabulate because of a rupture in a tiny blood vessel in the brain called the anterior communicating artery (ACoA). The rupture of this tiny artery temporarily cuts off the normal flow of oxygenated blood to areas of the brain that are essential to the proper recall of memories. The damage caused by an ACoA rupture can vary from one person to another, both in the location and the degree of damage. And the symptoms are also diverse: the person can suffer memory impairment alone, or memory impairment accompanied by confabulation.
When the ACoA balloons into an aneurysm and bursts, part of the frontal lobethe region of the brain behind the foreheadis starved of oxygenated blood. This condition, known as hypoxia, can lead to the death of brain cells. An area at the bottom of the brain, the basal forebrain, can also suffer damage. For reasons not entirely clear, damage to the basal forebrain can impair the ability to form lasting memories from recent experiences, a condition known as anterograde amnesia.
Confabulation in ACoA patients takes two forms. One involves distortions of when a particular remembered event actually occurredwhat DeLuca calls its "temporal context." The other type of confabulation is marked by distortions in what actually occurredthe actual content of a memory.
For instance, when asked what he did the previous weekend, one of DeLuca's ACoA patients said that he spent time with an old friend, visited New York City, and stopped by his store. Then the patient mentioned that the store was no longer in operation, contradicting himself. Furthermore, since the man had not left the hospital in the previous three weeks, much less traveled to New York City, the whole story was a confabulation. He had distorted both the when and the what of his memory.
Yet this patient was totally unaware of the errors in his memory of the weekend. This reflects an aspect of confabulation known as impaired self monitoring. "Normally we're able to filter out what doesn't fit with the context of what we're doing or saying," DeLuca says. "But apparently, people who confabulate are having a breakdown in that. The system that tells them it's not right isn't working. Thats the frontal lobes."
The frontal lobes are important to the "executive" functions of the mind, including self monitoring, or awareness of ones own behavior. In confabulation, self monitoring is crippled. This is what allows a confabulating ACoA patient to recall impossible or improbable events without realizing it.
The picture of human memory emerging from research on confabulation doesnt match the popular misconception of memory as a computerlike system that simply stores and retrieves information. Instead, DeLuca emphasizes, memory is a "reconstructive process" that pieces together rough drafts of an event based on a lifetime of experiences and perceptions. And being imperfect, human memory needs something to check up on it: call it the executive within. Deprived of this executive within, the confabulating patient mixes fact and fiction and the order of particular events.
DeLuca is quick to emphasize, however, that ACoA patients who confabulate are not deliberately attempting to deceive anyone. Some psychiatrists, he says, still assume that confabulation is an amnesic patients way of filling in lost details to save face. However, DeLuca sees little evidence for that in his research. "They really believe with conviction that what they're saying is absolutely true," he says.
At the Kessler Medical Rehabilitation Research and Education Corporation, where DeLuca and his colleagues conduct their research, neuropsychologists, physicians, and therapists help people with confabulation to become aware that some of the memories they recall, believe, and even passionately defend are inaccurate. As awareness of the confabulation grows, the person confabulates less. Just how and why this happens is unknown. But gradually, over a period of weeks to months, most patients stop reporting inaccurate memories. The amnesia generally persists, but the executive within has returned to his desk.
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