送交者: bluesea 于 2005-2-18, 16:08:40:
Science Points to a 'Sixth Sense'
Thu Feb 17,11:47 PM ET Health - HealthDay
By Ed Edelson
HealthDay Reporter
THURSDAY, Feb. 17 (HealthDay News) -- Ever get a gut feeling something just isn't quite right, and make a decision accordingly? Science is beginning to suggest those instincts may have roots deep in the brain.
Research in young volunteers points to some kind of "sixth sense" -- a mechanism in the brain that picks up on subtle clues, then sends out subconscious signals of trouble ahead.
The finding could help explain certain intuitive phenomena seen among humans. For example, in the recent Asian tsunami, aboriginal people sought out higher ground in the moments before the disaster, as did many wild animals. Could subtle changes in weather or the environment have warned them early on?
Just such an early warning system may exist in the anterior cingulate cortex, a brain area important in processing complex information, according to a report by psychologists at Washington University in St. Louis. Their findings appear in the Feb. 18 issue of the journal Science.
In their experiments, the researchers challenged healthy young volunteers to a series of tricky visual tests aimed at setting up conflicting choices within the brain, explained Joshua Brown, a research associate in psychology who performed the study with Todd Braver, an associate professor of psychology.
During the experiments, the St. Louis team observed each participant's real-time brain activity using functional magnetic resonance imaging (fMRI).
"We used a situation where we presented signals on a computer screen," Brown said. "If it was an arrow pointing left, they pushed the left button. If it pointed right, they pushed the right button."
But then the tricks began. First, the computer screen would occasionally show a larger arrow that required a participant to push a button other than the one just indicated by a first arrow. The time at which the second arrow was presented was gradually made longer, so that a participant was more likely to have pushed the wrong button.
Second, the arrow signals were preceded by colored dashes -- white for left, blue for right. The experiments were rigged so that participants eventually had an error rate of about 50 percent when shown a blue dash, but only 4 percent when shown a white dash.
While the volunteers weren't told of the rigging, "some of them had begun to figure it out, at least on a subconscious level," Brown said. As this dawning awareness emerged, the fMRI images showed increased activity in the anterior singulate cortex whenever the blue dash was flashed.
"The purpose was to see if the brain picked up on the blue color being associated with a large number of errors," Brown said. "It appears that this part of the brain is somehow figuring out things without you necessarily having to be consciously aware of it."
The report "has the potential of unifying different approaches to the anterior cingulate cortex," said William J. Gehring, associate professor of psychology at the University of Michigan. "Researchers have been looking at the response to errors people make and also the response to negative events. This is tying those two together."
Still, Gehring said, "this is the sort of thing where you need additional research. The report is not specific about what is going on, and how closely the response is tied to awareness."
Gehring and Brown agreed that the findings have potential applications to psychiatric practice, but they lie far in the future.
Abnormalities of the anterior cingulate cortex have been associated with a number of mental illnesses, including schizophrenia, Brown said.
"It's a little premature to say how this might help us treat individuals with mental illness," he said. "There's a lot we don't know about what goes wrong in mental illness. But if we understand how this works in healthy individuals, we will be in a better position to understand what goes wrong in mental illness."
Abnormal activity of the anterior cingular cortex has been linked to obsessive-compulsive disorder, Gehring said. "It's been shown that there is too much activity in this area. There is a general sense that things are going wrong, when actually they are not."
More information
A simple introduction to brain function is available from the University of Washington.