Is there a brain basis to ADHD?

20 April 2013

Interview with

Professor Trevor Robbins, Cambridge University

Hannah -   So, other than the symptoms that people with the disorder present, what other ways can we start to understand it?  To find out, I visited Professor Trevor Robbins who's head of the Behavioural and Clinical Neuroscience Institute at Cambridge University.

Trevor -   So, then going to the other levels of analysis, the psychological level, we can ask the question, what is impulsivity, and abnormality as a reward system?  For example, we can ask whether ADHD individuals are somehow understimulated or underaroused so that they need to indulge in this overactivity to get themselves to a natural level of behaviour. We can ask whether they have problems with reward or is there problems in what we called executive control of their behaviour, which is often the case for example if your frontal lobes are impaired in the brain. 

At the brain level, we can use quite a lot of evidence from brain imaging to show for example that in ADHD, there are problems in areas like the frontal lobes so the grey matter may not be fully formed in these areas, or maybe the connections between different areas don't form particularly well and there is certainly emerging evidence for that. 

There may also be biochemical evidence in the brain of abnormalities.  For example, in the neurotransmitters dopamine or noradrenaline and they've been focused on a lot because these neurotransmitters which are of course chemical messengers are affected by the drugs which are customarily used to treat ADHD.  So for most among these is Ritalin, also called methylphenidate which is a kind of amphetamine and amphetamine itself is also used under the name of Adderall.  And methylphenidate increases the levels of dopamine and noradrenaline that are available to stimulate the nerve cells.  It does this by blocking a molecule called the transporter which stops these neurotransmitters being catabolised or metabolised.  Instead, they're taken back up into the nerve cells.  So that's very interesting.  The fact that these drugs like Ritalin and amphetamine works, suggests that there is some abnormality possibly in these transmitters.

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