My son Peter, who is ADHD and autistic, pointed me to several articles reporting research, conducted at The University of Nottingham in Great Britain, on children with attention deficit / hyperactivity disorder that suggests what goes wrong,
There’s a part of the brain that is working whenever people aren’t doing anything in particular. It’s called the “default mode network (DMN)” — it’s what your brain is doing when you’re daydreaming. and it’s inactive when you are paying close attention. It’s been known that people with ADHD have difficulty turning off the network.
The researchers compared magnetic resonance images of children playing a computer game. For children in the control group, who did not have ADHD, the network was inactive while they were playing the game, while the children who had been diagnosed were always being distracted by something the daydreaming part of their brain happened to notice.
So much is not entirely new, but what the researchers found is that if the children were taking their medication (Ritalin, or some other form of methylphenidate) their mri scans looked like the scans of the children in the control group. But that wasn’t the only way to affect the scans; making the game more exciting, for instance by increasing the incentives to do well, also made their brain activity resemble that of the control group. That suggests a reason why ADHD children can sometimes focus with great attention over long periods on something that intensely interests them. And when they don’t they are not merely being contrary.
Science Daily reported:
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 off the DMN and would perform poorly. This effect of incentives was not seen in children without ADHD — activity in their DMN was switched off by items requiring their attention regardless of the incentive on offer.
The university’s press release is here, and the paper, published in the Journal of Child Psychology and Psychiatry, is “Task-related Default Mode Network modulation and inhibitory control in ADHD: effects of motivation and methylphenidate.” Information about this and previous papers are here.
UPDATE: Peter comments: “[The research is ] of interest to me because it’s such a very good description of what goes wrong with my brain. It also, I think, explains why fidgets work so well for helping me focus; if I’m fidgeting, the default mode network can busy itself fidgeting while I go pay attention to something else.”