Previous studies have shown that children with ADHD have difficulty in 'switching-off' the default mode network (DMN) in their brains. This network is usually active when we are doing nothing, giving rise to spontaneous thoughts or 'daydreams', but is suppressed when we are focused on the task before us. In children with ADHD, however, it is thought that the DMN may be insufficiently suppressed on 'boring' tasks that require focused attention.
The MIDAS group researchers, which included Dr Martin Batty and Dr Elizabeth Liddle, compared brain scans of 18 children with ADHD, aged between nine and 15 years old, against scans of a similar group of children without the condition as both groups took part in a task designed to test how well they were able to control their behaviour. The children with ADHD were tested when they were taking their methylphenidate and when they were off their medication. The findings are published in the Journal of Child Psychology and Psychiatry.
Whilst lying in a magnetic resonance imaging (MRI) scanner, which can be used to measure activity in the brain, the children played a computer game in which green aliens were randomly interspersed with less frequent black aliens, each appearing for a short interval. Their task was to 'catch' as many green aliens as possible, while avoiding catching black aliens. For each slow or missed response, they would lose one point; they would gain one point for each timely response.
To study the effect of incentives, the reward for avoiding catching the black alien was then increased to five points, with a five-point penalty incurred for catching the wrong alien.
By studying the brain scans, the researchers were able to show that typically developing children switched off their DMN network whenever they saw an item requiring their attention. However, unless the incentive was high, or they had taken their medication, the children with ADHD would fail to switch o
|Contact: Lindsay Brooke|
University of Nottingham