ERROR DETECTION IN THE GRAY MATTER
Have Scientists Discovered Intuition?
Memories of 1999, after all, are still fresh. Eight years ago, when the Mars Polar Lander space probe entered the atmosphere of the red planet, radio contact was suddenly lost. The satellite simply disappeared from the screens at the control center. Four hundred million dollars had vanished into silence.
The brain knows more than we sometimes give it credit for. Those subtle feelings of foreboding may be your gray matter telling you that you've made a mistake.
The two managers in charge of the project were convinced that they would be fired without further ado. "That's how we deal with errors in our culture," says Markus Ullsperger. But this time, the managers were spared, Ullsperger, a brain researcher at the Cologne-based Max Planck Institute for Neurological Research, recounts. "And it was a good decision," he says. "After all, millions had been invested in their training and education."
From the standpoint of neuropsychology, this was an excellent management decision. Errors, Ullsperger is convinced, are in fact one of the most valuable sources of knowledge. "A man's errors are his portals of discovery," Irish writer James Joyce once said, anticipating a conclusion modern neuroscience has now confirmed.
Ability to Detect its Own Errors
Ullsperger, like a dozen other research teams around the world, is currently studying how the brain tracks down and processes its own errors. "Our brain has the fascinating ability to detect errors and, if they have already occurred, to learn from the experience," he explains.
"Error-related negativity" (ERN) is a concept that has captivated the scientific world. It refers to a characteristic wave of voltage beneath the skullcap, which can be measured whenever the brain detects that an error has been made. Especially surprising is the fact the ERN signal already begins to flicker even before a person is aware of his error.
In the early 1990s, Michael Falkenstein, a neurophysiologist from the western German city of Dortmund, observed for the first time how voltage declines by at least 10 microvolts in a specific group of nerve cells, and that this occurs only 100 milliseconds after a person has made an error -- about the time it takes for your cursor to respond to a click of the mouse.
Falkenstein's discovery marked the beginning of a period of systematic study of the brain's fine-tuned error detector. It paved the way for fascinating new theories on questions such as why compulsive disorders occur or why some people hesitate while others make confident decisions. It also shines a new light on the development of addiction.
Suddenly it becomes clear why a person can often avoid making a certain mistake based purely on gut feeling. "The experiences of the error system provide precisely that subconscious knowledge on which intuition is based," explains Ullsperger.
Vaguely Uneasy Feeling
The error system acts in two ways. First, it intervenes in a corrective way when a person has committed an error. But it also has a warning capability. When it recognizes that an action may not lead to the desired outcome, this recognition is expressed in a vaguely uneasy feeling.
Ullsperger and his fellow researchers plan to find out exactly how this works, using a functional nuclear magnetic resonance (NMR) scanner. Research subjects lying in the NMR tube undergo simple tests, such as the Eriksen-Flanker task, a common and well-known tool of neuroscientists. In the test, rows of letters, like SSHSS, SSSSS or HHSHH flicker in front of the subjects' eyes. They are then asked to press one of two buttons: the left button if the letter in the middle is S and the right button if it is H.
This isn't as easy as seems. The letters to the right and left of the main letters confuse the observer. Especially when they are given only a limited amount of time to perform the task, the subjects frequently correct their answers a few moments later. "They behave the way we do when we misspeak, notice the error and then quickly correct our sentence," says Ullsperger.
Electrodes in a rubber cap on the subject's head measure the typical ERN waves flickering through the brain during this process. Meanwhile, the NMR scanner observes the area of the brain in which nerve cells are especially active.
Stops Producing Dopamine
The method makes it possible to replicate the anatomy of error detection. What it reveals is that immediately following the ERN wave, the midbrain suddenly stops producing dopamine. This neurochemical signal is transferred to the basal ganglia and thus into the limbic system, in which emotions are generated.
Researchers have also discovered another nerve cord involved in error detection. It leads to a deep section of the cortex, which then broadly distributes the signal in the cerebral cortex. "This cascade sends the following signals to the executive positions: Stop, something is going wrong here! Check again and, if necessary, correct immediately," explains Ullsperger.
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