Though you’ve been told your child has attention deficit hyperactivity disorder (ADHD), you simply cannot understand what is going on beneath the surface. Why can’t the school psychiatrist explain what causes your kid to become distracted? A new study from scientists at the University of Michigan may ease your mind while providing much-needed insight into that of your child. By examining brain scans of affected and normal children, they discovered a key difference between the brain wiring of kids with ADHD and those without. Children and teens with ADHD, their new study finds, lag behind age-group peers in how quickly their brains form connections within, between, and among key brain grids: the default mode network and the task-positive networks.

Connectomics and the Future of Neuroscience

In the last decade, functional magnetic resonance imaging (fMRI) scans have revealed not just the physical structure of the human brain, but how the brain organizes itself into large-scale connectivity networks, which mature throughout early childhood all the way to young adulthood. A field known as connectomics is the study of these connections in the brain. Using the most recent technology, connectomic scientists observe not just the one-to-one communications between two specific brain regions, but whole patterns of activity and collaboration among thousands of nodes within the brain.

For the current study, Dr. Chandra Sripada, an assistant professor in the Department of Psychiatry at the University of Michigan Medical School, and a team of colleagues looked at the brain scans of 275 kids and teens with ADHD, and 481 unaffected age-group peers, using connectomic methods. The fMRI scans showed brain activity during a resting state, highlighting the ways in which a number of different and specialized brain networks communicated among themselves. After examining and comparing scans, the researchers discovered lags in development of connection and isolated where these lags occurred — within the internally-focused network, called the default mode network or DMN, and in development of connections between DMN and two networks that process externally-focused tasks, often called task-positive networks, or TPNs.

Bizarrely, a great deal of activity occurs in your brain whenever you are doing nothing at all. When you are daydreaming and your brain has returned to default mode, dispersed areas within your brain, the DMN, are busy messaging one another. Shockingly, your brain is so busy while you are daydreaming, say, the energy consumed by the DMN is about 20 times that used by the TPNs, the areas of the brain that respond to outside stimulus and complete necessary tasks.

The team believes their findings might help other researchers better understand the longitudinal course of ADHD from childhood to adulthood. For instance, some children and teens "grow out" of the disorder, while the disorder persists throughout adulthood in others. "This study provides a coarse-grained understanding, and now we want to examine this phenomenon in a more fine-grained way that might lead us to a true biological marker, or neuromarker, for ADHD," said Sripada. Ultimately, understanding the neural mechanisms of ADHD should lead to better diagnosis and treatment.

Source: Sripada C, et al. Proceedings of the National Academy of Sciences. 2014.