image by U.S. Army (lic)More recently, ADHD researchers have directed their attention to the cerebellum. Studies indicate the cerebellums of children with ADHD are notably smaller than their non-ADHD peers. The cerebellum is a brain region that plays a significant role in sensory perception and motor function. As such, a smaller cerebellum might account for ADHD symptoms such as impulsivity, and the tendency to act without thinking.
A smaller brain may impair executive functioning. This is a term psychologists use to refer to higher-order thinking skills, such as the ability to organize information; to sustain attention; and to choose an appropriate course of action. Many professionals suspect that impaired executive functioning can account for many ADHD symptoms.
Other research suggests there may be a subset of children with ADHD who have larger frontal lobes than average. These children seem to have predominately hyperactive behavior. Research also suggests that ADHD may affect the basal ganglia connection to the frontal lobe. The basal ganglia are brain structures that help to coordinate motor control, cognition, emotions, and learning. These preliminary findings seem to indicate that not only are there brain differences between people with ADHD and those without the disorder; but, there may also be brain differences among the three ADHD subtypes. LINK More research is needed to determine whether there are truly biological differences in structure and function between different ADHD subtypes.
It is important to note we do not know if these brain differences are the cause of ADHD symptoms. These differences could be a cause, a consequence, or of no consequence. At this point, we can merely observe differences and speculate plausible explanations based on what we do know.
Continuing with brain differences, some researchers have found that children with lesser amounts of gray matter have a harder time paying attention. Gray matter is a connective tissue in the brain. It facilitates communication within the brain. Several studies indicate that ADHD individuals have less gray matter. This suggests a possible link between brain structure and ADHD behaviors.
In addition to differences in brain structures, differences in brain activity can also be found. Brain activity can be measured by imaging technology such as Magnetic Resonance Imaging (MRI). During tasks that require careful attention and impulse control, individuals with ADHD show decreased activity in the striatum and the prefrontal cortex. These parts of the brain modulate movement, decision-making, and response to rewarding or unpleasant situations. These findings might account for the non-traditional learning styles in people with ADHD.
Although brain imaging techniques are useful for research, they are not currently used to diagnose ADHD. These types of studies provide helpful clues about the causes of this disorder. Someday research may determine the precise cause of ADHD. Until then, we can merely observe these differences and theorize causal relationships to ADHD symptoms. It is also important to note that these brain differences do not affect intelligence or other types of abilities. People with ADHD can be very smart, creative, athletic, and social. They can also be hopeful and optimistic; or, they can be depressed and discouraged. Thus, ADHD does not define a person. The unique brain differences described here reflect a genetic process that affects a specific set of tendencies and behaviors. It does not affect the entire range of a person's skills and abilities.