Cutting edge: Jeffery Schall

January 26, 2001

Forget the homunculus - the brain may have a supervisory system that helps it to learn from success and to correct mistakes

When the young executive asked the retiring CEO how he had learnt to make so many good decisions over his career, the CEO replied: "By making so many bad decisions." In my laboratory, we are investigating how the brain makes decisions and produces movements to obtain goals. We recently discovered a part of the brain that appears to evaluate the consequences of actions.

Learning how the brain works is like learning how a computer works. One must analyse the signals produced by individual components of the circuit. We obtain our data by monitoring the activity of neurones in monkeys that perform tasks to earn a reward. We recently adapted an experiment developed by cognitive psychologists to study how humans control their behaviour. In successive trials, subjects are asked to respond as quickly as possible to a stimulus simply by looking at it. But in rare, randomly selected trials, subjects receive a second stimulus shortly after the first, telling them not to respond as previously instructed. Sometimes subjects are able to withhold the movement in time. Sometimes they are not.

Several brain structures respond to stimuli and produce movements. We have previously studied how neurones in one part of the brain decide which stimuli from among a collection to respond to and how other neurones control whether or not to produce the movement. In work just published in Nature , we describe signals produced by neurones in yet another part of the brain. Some brain cells were activated when errors were produced. The activation of these neurones in the monkeys probably contributes to a neural signal observed in humans under similar conditions. Therefore, we believe they are part of a brain system activated when you make a mistake and experience an "oops" sensation. Other neurones were activated when the subject was successful. We believe these neurones are part of a system in the brain that is activated when you achieve success under challenging conditions and experience a "yippee" sensation.

A hallmark of intelligent behaviour is the ability to learn from success and to correct mistakes. It seems that the parts of the brain responsible for responding to stimuli and producing movements have their hands full, so to speak. We believe that the signals we observed are part of a supervisory, executive system that monitors the consequences of actions. This hypothesis takes a key step towards banishing the popular idea of the homunculus - the little person in the head who was supposed to be the agent of intelligence. Our and other groups' research in cognitive neuroscience identifies free will with brain function.

One is often asked about the practical benefits of research such as this. The justification could not be more straightforward - if you do not know how something works, you cannot fix it. Disorders such as schizophrenia are characterised by impaired control of thought and action. Hope for prevention or cure of mental disorders springs from basic research on brain function; that is why our research was funded by the National Institute of Mental Health. But such utilitarian goals are inspired by the insights derived from basic research on the brain. With more government support, sustained by public interest, research on how the brain produces thought and emotion could effect a change in humanity's conception of its place in the universe comparable to that effected by Copernicus and Darwin.

Jeffrey Schall is professor of psychology and director of the Vanderbilt Vision Research Center at Vanderbilt University, Nashville, United States.

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