Understanding Attention Deficit/Hyperactivity Disorder (ADHD) Part 2

In part two of my latest series on attention deficit/hyperactivity disorder (ADHD) we take a closer look at the nature of the disorder.

These positron emission tomography (PET) scans show that patients with ADHD had lower levels of dopamine transporters in the nucleus accumbens, a part of the brain’s reward center, than control subjects.

What is attention deficit/hyperactivity disorder?

Do you remember a classmate who just could not sit still or another who just sat quietly in the corner, day dreaming and looking out the window but when called on by the teacher did not know what was going on? Today both of these children might be diagnosed with ADHD. Indeed some still argue that there is no such thing as ADHD – that it is an artificially conceived diagnosis to aid the selling of prescription drugs and that in previous times a child with ‘ADHD’ was no more than considered to be no more than ‘bored’,’ restless’ or ‘giddy’.


ADHD was first described more than 100 years ago and its symptoms include excessively inattentive, hyperactive, or impulsive behaviours. For instance, children with ADHD find it more difficult to focus and to complete their schoolwork. ADHD affects up to eight in one hundred children and in over half the cases, it continues to persist into adulthood.Although most individuals with ADHD do not outgrow the disorder, their symptoms often change as they grow older, with less hyperactivity as adults. Problems with attention tend to continue into adulthood. There is no cure for ADHD at this time.

Possible causes

Recent brain imaging studies have shown a reduction in the levels of the neurotransmitters dopamine and noradrenaline in at least some people with the disorder. Because the nerve circuits in the prefrontal brain regions, which are normally involved in attention, require high levels of dopamine and noradrenaline stimulation, reduced levels of these two neurotransmitters could potentially lead to the weakened regulation of attention and behavior observed in ADHD .Altered brain activity also has been observed in particular nerve circuits connecting the cortex (outer part), striatum (deeper parts), and cerebellum (back of the neck), particularly in the right brain hemisphere with a delay in cortical development seen in some children with ADHD.
In part three of this series,  I will explain more what neuroscientists mean by ‘attention’, where it is found in the brain and how it is affected in ADHD.

Other Sources:

Part 1: Understanding ADHD and Learning Disability