Researchers combined 11 brain scan studies that looked at how the brain handles timing tasks. Together the studies covered 150 people with ADHD and 145 people without it. Most of the data came from children, with 9 of the datasets in young people and only 2 in adults, so the results lean toward children and teens.
During timing tasks, the ADHD group showed less brain activity than the comparison group in a few areas. These included part of the front left of the brain along with the insula, the cerebellum, and a region toward the lower back and side of the brain. In one region toward the back, the precuneus and nearby areas, the pattern flipped and the ADHD group showed more activity than the comparison group.
The team also looked at medication. Lower activity in a front region called the right DLPFC showed up in people who had never taken stimulant medication, but it looked normal in people on long-term stimulants. This medication result rested on only two never-medicated samples, and close to half the patients were on medication (47%), so it is not firm.
Only 13% of patients had another condition, so the analysis could not say much about that.
Source: Heledd Hart, Joaquim Raduà, David Mataix‐Cols, et al.. Meta-analysis of fMRI studies of timing in attention-deficit hyperactivity disorder (ADHD). Neuroscience & Biobehavioral Reviews (2012). doi:10.1016/j.neubiorev.2012.08.003
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