What Is ADHD?

Attention Deficit Hyperactivity Disorder

It is not laziness, an excuse for irresponsibility, or a fictitious disorder. ADHD has a long history.  In the 1800s, the symptoms we commonly attribute to ADHD were originally observed in the behavior of individuals with injuries to the front of their head.  These individuals would act impulsively, not have a “filter” and blurt things out, often rudely and crudely. They would get into fights and behaved “out of character.” They become easily distracted and often would fail to finish their work or frequently change the topic of their conversation. They couldn’t sit still. Their short-memory became impaired and they would forget things or misplace them. Their ability to plan and organize their work activities became impaired. Upon autopsy, these deceased patients would have brain damage in their pre-frontal cortex and striatum. The term “organic brain damage” emerged to label their condition.  Individuals who behaved similarly to those with organic brain damage were believed to have the same neurological damage. However, over the years, many individuals showed no signs of organic damage upon autopsy. So it was believed that their damage was minimal, or perhaps in the wiring of the brain itself and, therefore was not visible to the eye or the microscope. The term, minimal brain damage or MBD emerged to explain this condition.

As the education system grew in this country, children were required to participate in public school education. Teachers found a segment of their classroom population difficult to teach.  When the psychological testing movement arrived, children with subnormal intelligence could be identified, explaining why they were having learning problems. Other children were having difficulty learning despite their average or above average intelligence.  A portion of these children were not behavior problems, they had learning disabilities (e.g., Dyslexia).  However, about 5 to 10% of the children in school with difficulty learning, had behavioral symptoms  similar to individuals with MBD. However, there were problems with this diagnosis.  More boys than girls were being identified as having MBD and children who were quiet but struggling academically were being ignored. In the 1900s, the field of psychology was becoming recognized as a science, applying statistical models to the measurement of normative human behavior. Psychologists studied children who were of average or above in intelligence, but hyperactive to determine whether their hyperactivity made them different in their ability follow teacher instructions and learn to read, write and calculate. In the meanwhile, the medical community began to emphasize observable behavior in diagnostics which led to the change in terminology from MBD to “Hyperactivity Disorder.” Over the next years of experimental study of children with Hyperactivity Disorder, psychologists found that hyperactivity and inattention, both separately and combined, were associated with behavioral problems leading to poor achievement. So, “attention” emerged as another key variable in identifying the behavior and learning problems of these children.

With the merging sciences of neurology and psychology and successful use of stimulant medication to treat many children with ADHD, the theory emerged that these children lacked production of specific neurotransmitters in the prefrontal cortex and striatum.  The healthy prefrontal cortex and striatum are responsible for the executive functions: planning, organizing, paying attention, resisting distraction, regulating mood, and thinking before acting. ADHD symptoms are a result of deficits in the executor and result in impulsivity, inattention, distractibility, disorganization, poor planning, hyperactivity, and acting without considering the consequences of their behavior.

ADHD studies using the latest technology in brain imaging show the location of structural impairments in executive functioning in the brain. The SPECT (single photon computer tomography) images below, of the prefrontal undersurface view of the normal and ADHD unmedicated and medicated brains, show the anatomical deficits associated with the executive functions. You can see the areas that are impaired in the middle and right images below, compared to the normal view on the slide on the left.  The “holes” or dark areas represent the cooler areas where the brain is not giving off much heat.  In the image of the medicated brain, on the right, the holes appear to be more smaller, but are actually warmer areas of improved brain activity.

 ADHD SPECT Image

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