27 November 2012
Our brain appears to be well prepared for what needs to happen after an error has been made in order to avoid another error. It determes if we need to be less guided by impulses or if we should refocus our attention. The researchers - Joram van Driel, Richard Ridderinkhof and Mike Cohen – make a convincing case for the existence of two subsystems in the brain. These subsystems differ both in terms of the network of brain regions that are active (front areas versus back areas of the brain) and the language with which they communicate (theta waves versus alpha waves).
It was already common knowledge in Neuroscience that brain responses to errors are very strong and that a network of brain areas is activated within one hundred milliseconds. As a result, the brain finds itself in a more alert state, so that the same error is not made. The brain is thus capable of detecting an error rapidly. Not every error is the same. Some errors are an impulsive response to a cue from the environment (if someone, for example, reaches for a failing plant, which turns out to be a cactus), while other errors are caused by attention lapses (if a person’s mind wanders leading him or her to drive through a red light).
While brain activity was being measured with an electro-encephalogram (EEG), the researchers made subjects perform various tasks that are known to bring about many errors. Subjects performed, for example, a so-called ‘Simon task’, in which they had to respond to a blue or yellow circle with their left hand and a green or red circle with their right hand. The circles could appear on both the left and right sides of the screen. The subjects had to therefore pay attention to the colour and not the location.
When impulsive errors are made, the brain is guided by the (task-irrelevant) location when the colour and location do not match. In those cases, there is an immediate response: amplified theta waves (brain waves of around 6 Hertz) were observed in the central frontal region of the brain which communicated that more control was needed to the other lateral frontal parts of the brain. However, when the colour and location not matching could be perfectly predicted, the attention of the subjects quickly lapsed. The task becomes easier in this instance, but the subject still makes errors. When this happens, the theta activity can be seen to decrease slightly, while the suppression of alpha waves (around 10 Hertz) greatly increases at the back of the brain slightly later. Reduced alpha waves represent increased attention.
The research is important for further scientific research. But it also has social and clinical implications, for instance in relation to children with ADHD. Research can reveal whether an individual child with ADHD is primarily struggling with impulsive actions or with wandering attention, and how this is reflected in the types of errors that these children make in the classroom. As a result, it’s possible to establish the extent to which brain mechanisms for maintaining adequate control after making errors caused by impulsiveness or lapses in attention exist, and the effect of therapy or medication on these mechanisms.
Joram van Driel, K. Richard Ridderinkhof & Michael X. Cohen: ‘Errors Are Not All Alike: Theta and Alpha EEC Dynamics Relate to Differences in Error Processing Dynamics' in The Journal of Neuroscience (21 November 2012).