ADHD Neurobiology
Children with ADHD suffer from a brain-based biological disorder. They have lower levels of dopamine, a neurotransmitter. In addition, brain-imaging including MRIs and PET scans show that brain metabolism is lower in patients with ADHD than in normal controls, with significantly lower metabolic activity in regions of the brain that control attention, social judgment and movement.
Brain Imaging – Structural
The cerebral cortex is broken up into 4 lobes: frontal, occipital, parietal and temporal
Brain imaging studies suggest the frontal cortex is involved in ADHD
The frontal cortex is involved mainly with executive functions:
- problem solving
- attention
- reasoning
- planning
ADHD suffers usually have deficits in these functions.
- these deficits become obvious in tests that are used during diagnosis, such as the Stroop test.
| The brain has two hemispheres. The left is responsible for language and calculation, while the right is involved in attention. |
- some evidence suggests the right frontal lobe is smaller in children with ADHD than non-ADHD children
- the right side of the brain is generally considered to be involved in attention processes
- People with ADHD and people who have suffered frontal lobe damage or right hemisphere damage through illness or accident have similar symptoms
Brain Imaging – Functional
functional imaging techniques (SPECT & fMRI) allow us to view the brain while it works
Functional studies of ADHD demonstrate:
- a decrease in the metabolic activity in the right frontal lobe
- a decrease in the metabolic activity in the basal ganglia which is responsible for regulating movement and is connected with the frontal lobe region
- 3 areas closely related to the basal ganglia are believed to be responsible for the symptoms of ADHD:
(Click on the name to see where in the brain each region is)
- the prefrontal cortex (part of the frontal lobe) ,thought to be the brain’s “command center”
- the caudate nucleus (part of the basal ganglia)
- the globus pallidus (part of the basal ganglia)
Some researchers believe that problems in the circuit between these three regions are the underlying mechanisms that cause ADHD symptoms.
Prefrontal Cortex
Marked areas:
A. Spatial working memory
B. Spatial working memory, performance of self-ordered tasks
C. Spatial, object and verbal working memory, self-ordered tasks, analytic reasoning
D. Object working memory, analytic reasoning
Image from Scientific American
Caudate
Globus Pallidus
This image was produced by the Digital Anatomist Project