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12 December 2013 1:00 pm ,
Vol. 342 ,
In an ambitious project to study 1000 years of sickness and health, researchers are excavating the graveyard of the now...
Stefan Behnisch has won awards for designing science labs and other buildings that are smart, sustainable, and...
The iconic 125-year-old Lick Observatory on Mount Hamilton near San Jose, California, is facing the threat of closure...
Recent results from the Curiosity Mars rover have helped scientists formulate a plan for the next phase of its mission...
A new, remarkably powerful drug that cripples the hepatitis C virus (HCV) came to market last week, but it sells for $...
In pretoothbrush populations, gumlines would often be marred by a thick, visible crust of calcium phosphate, food...
Evolutionary biologists have long studied how the Mexican tetra, a drab fish that lives in rivers and creeks but has...
Victorian astronomers spent countless hours laboriously charting the positions of stars in the sky. Such sky mapping,...
- 12 December 2013 1:00 pm , Vol. 342 , #6164
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A Mind Deceived by the Past
22 June 1999 3:30 pm
Besides forgetting their spouses' birthdays or where they left their car keys, some amnesiacs confabulate--that is, they invent stories that they believe are true. In this month's issue of Nature Neuroscience, researchers provide evidence that the fantasies come from old memories dredged up by associations with contemporary situations. The findings suggest that an area of the brain implicated in emotion and rewarding behavior is important for constructing a sense of present reality.
Confabulators can tell some pretty strange tales: Take the case of a former dentist who would leave the hospital telling the nurse that he had patients waiting. The stories are almost always rooted in past experiences, although confabulators confuse when the events happened. A woman may want to drop what she's doing and feed her baby, even though her "baby" is 35 years old.
Wondering whether confabulators are failing to suppress old memories, a team led by Armin Schnider at University Hospital in Geneva, Switzerland, showed a series of pictures, some turning up more than once, to 12 nonconfabulating amnesiacs, six confabulating amnesiacs, and 10 control subjects. In three consecutive experiments, participants were asked to identify which pictures were repeated in each series. The team stacked each deck with pictures shown in a previous experiment but appearing only once in the current trial.
Both groups of amnesiacs fared worse than controls at picking out the repeated pictures, but only the confabulators fell for the red herrings from earlier experiments. "They cannot suppress information which they have seen before but which is not relevant now," says Schnider. The confabulating patients all had damage to areas of the brain that make up the anterior limbic system, which set them apart from the other subjects. Schnider suggests that this region exerts an influence on the mind and "allows you to base your thinking and actions on current reality."
"It's beautiful data," says neuroscientist Tim Shallice of University College London. This is the first time anyone has proposed a suppression mechanism to explain confabulations, he says, but the idea fits nicely with some previous findings.