Professor Philip Shaw discusses three brain areas in relation to the neuropathology of ADHD: the frontal cortex, amygdala, and hippocampus.

I think the part of the brain that is most consistently implicated in ADHD that people most reliably find that there is some structural difference, is in the frontal cortex, the front parts of the brain. Within that, it is the dorsolateral prefrontal cortex, the part on the side (about here), that most groups find is different in kids with ADHD, that’s kind of regardless of which measure you use. So, it’s a bit smaller in volume. If you look at cortical thickness, it tends to be a bit thinner. There does seem to be a very consistent finding that that area of the brain is structurally compromised. And then, of course, the assumption is because that’s got a structural difference, does this lead to functional differences? And if you look at studies which use functional imaging to look at how the brain is active whenever kids with ADHD are doing certain tasks, you do indeed find differences in those parts of the brain, as well. So that’s a very convincing story, I think, for the prefrontal cortex, that is, both structural compromise, structural differences, and also differences in functional activity. For deeper structures in the brain, like the amygdala and the hippocampus, the findings are a lot less consistent. For the amygdala, which is a little almond-like structure that sits at the front of the temporal lobe, very much associated with emotional processing. Some people have found differences, some haven’t. Some have found, for example, very interesting shape differences in the amygdala, which might be relevant. One particularly interesting recent finding was that the connections between the amygdala and the frontal parts of the brain might be different in kids with ADHD. In terms of the hippocampus, again, it’s a complicated story for ADHD. One particularly interesting study actually found that the hippocampus was bigger in kids who had ADHD. And, the fewer symptoms they had, the bigger the hippocampus, which might suggest that the hippocampus getting bigger is compensating for the symptoms. So that’s one interesting finding in the hippocampus, but the most reliable findings are in the frontal cortex.

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