New studies using a variety of different technologies show interesting differences in the brains of people with A.D.D.
- Electroencephalogram (EEG) studies taking readings from the surface of the scalp reveal slower overall electrical activity.
- SPECT (single-photon emission computed tomography), which can look at deeper structures, have found reduced blood flow in the brain’s frontal area and limbic system, areas that are important for impulse inhibition, when the person with A.D.D. is under stress. This may explain the impulsiveness of children with A.D.D. Blood flow was also decreased in the area of the striatum, the part of the brain that processes motor inhibition. This may contribute to hyperactivity.
- PET (positron emission tomography) scans to study the brains of adults who were diagnosed with A.D.H.D. in childhood. A PET scan measures the rate of glucose metabolism in the brain, and indirect measurement of brain activity. PET scanning showed decreased glucose metabolism (that is, less activity) in the frontal region of the brain in the A.D.H.D. group. This suggests that people with A.D.H.D. process information differently, especially in the frontal lobe. This area of the brain, called the executive area, processes incoming information and selects out which information is relevant to the person, what needs to be acted on, and what should be ignored. To a child who has A.D.D., all information may seem equally important – the noise of the car passing by and the teacher’s lecture. His brain can’t selectively tune in to the teacher’s visual and verbal instructions while tuning out classroom and outside noises.
- Because some children with A.D.D. show dramatic improvement with stimulant medications, this finding provides a clue to the mechanisms of A.D.D. Stimulant medications are thought to work by increasing neurotransmitters, chemical messengers that are responsible for information processing throughout the brain. Since stimulant medications affect these neurochemicals, A.D.D. in some children is thought to be basically an imbalance of neurotransmitters.
- The studies correlating brain activity with A.D.D. are still preliminary, yet the evidence is accumulating that the brains of at least some of these children perform differently, especially the areas of the brain that process behavior and learning. Children with A.D.D. do have a biological difference that needs to be recognized, respected, and managed. These findings take the pressure off parents who may feel responsible for their child’s problems. They also diffuse the unfair accusations that these children are simply kids who were never properly disciplined. Research is proving what parents and teachers have long suspected: these kids behave and learn differently, so they need to be parented and taught differently.