Attention Deficit Hyperactivity Disorder | Different Perspectives

The Cognitive Model Attention Deficit Disorder

In the past decades several names have been given to this symptom cluster, including “hyperactive child syndrome, hyperkinetic reaction of childhood, minimal brain dysfunction, and attention deficit disorder (with or without hyperactivity)” (Barkley). This re-labelling of the disorder every decade has sparked confusion but also reflected the shifting understanding of the disorder.

In the early 1900’s George Still was the first physician to publish cases and papers on children with these specific symptoms. He believed the problems were a result of defects in moral control. Later, Strauss and Lehtinen (1947) suggested brain damage in children as the source of this problem. The focus shifted to the excessive motor activity in the 1950s and 1960s. A growing body of evidence in the 1970s suggested major deficits with attention and impulsivity (Douglas 1972).

Hyperactivity was relegated to a secondary position to these problems with attention and impulse control. However, the term Attention Deficit Disorders was entered in DSM-III only in 1980. Early in the last decade, scientists posited that the central issue was one of executive functioning. Presently, it is believed that Attention Deficit Disorder is an organic disorder, which effects communication in the brain’s management system, thus affecting the executive functions- Executive Function (EF) Deficit.

Executive Functions are a set of high-level cognitive abilities that govern and modify other more basic abilities like attention, memory and motor skills that are needed for goal-directed behaviour. Executive Functions help to decide when to initiate or stop actions, when to adapt behaviour as needed, and to plan future behaviour when dealing with newer tasks and situations. Executive functions allow us to foresee outcomes and adjust to changing situations.

Several scientists, like Brown and Barkley have tried to explain the executive function deficiency in ADD/H. Psychologist Dr. Thomas Brown has described EF as the focus needed to plan and control any ongoing activity. It is a complex, dynamic process of selecting and engaging what is important to notice, to do, to remember, moment to moment to accomplish a task. He described six aspects of executive functions that are impaired in ADD.

Dr. Russell Barkley argues that the inability to inhibit is the core problem in ADHD and of all the executive functions is the most important.

Biological Model of Attention Deficit (Hyperactive) Disorder

Dr. Alan Zametkin, a psychiatrist at the National Institutes of Health, published evidence from positron-emission tomography (PET) scans that showed ADD to be associated with at least one physical marker in the brain: lower levels of activity in the prefrontal cortex, from which planning and self-control proceed. This was an important study that gave evidence of the organic nature of this disorder and helped towards establishing it as a neurological disorder.

Zametkin studied 25 adults who were hyperactive in their childhood and who had children with similar symptoms and compared them to 50 adults who were apparently ‘normal’. The brain’s glucose utilisation was studied as a measure of energy used by the use of PET scans while the subjects performed an attention task requiring them to press a button upon hearing a tone. These subjects displayed reduced overall brain metabolism than the controls, with the greatest deficits seen in the areas controlling attention and motor activity.

Other researchers have suggested the condition has a genetic basis. Dr. Florence Levy demonstrated that ADD was seen in 81 percent of identical twins (who share identical genetic material) as compared to 29% in fraternal twins. Under-activity in the brain’s management system (major circuits that sustain executive functions) is typical of ADD syndrome. The brain regulates itself and the entire body via the constant interactions among these circuits. These processes work at the synapses or spaces between the neurons through the use of chemicals. These networks have to communicate rapidly with one another in order to manage the body, all mental functions, and the person’s ongoing interactions with the world.

Hence, ADD syndrome is essentially a chemical problem with impairment in the chemistry (that supports rapid and efficient communication) of the brain’s management system. It reflects impairments in the brain’s ability to process dopamine and norepinephrine.

Dopamine and Norepinephrine are the main neurotransmitters affected by ADD. Though produced in normal amounts in the individual with ADD are not adequately released or reloaded. This results in inefficient and inadequate carrying of the messages across the synapse.

The structures and physiological processes of the brain that sustain the EF of the brain are the most complex systems which develop, they are also the slowest to develop compared to the other aspects of the brain and then gradually decline in efficiency in some people with old age.

Circuits that support executive functions of the brain are distributed throughout the brain. They occupy three main areas. The prefrontal cortex that is mainly concerned with working memory, the Limbic system and the Reticular Activating Systems that deals with regulating alertness and vigilance.

Working memory is a network of neurons that very briefly hold perceptions and thoughts of the moment and link them with stored memories. The limbic system, which is concerned with assessing rewards and punishments, is a crucial element underlying multiple executive functions. The brain uses one chemical, dopamine to highlight important stimuli. It provides incentive for the brain to act when something important is noticed. It plays a critical role in mobilizing and sustaining effort to get what the individual needs or wants. Dopamine is called the chemistry of motivation.  Norepinephrine is the primary neurotransmitter secreted by the RAS. When fired it is distributed throughout the brain, increasing alertness and excitability. Lack of it results in drowsiness, inattention and sleep.

These various brain circuits are closely linked to the executive functions of the brain. They integrate perceptions, assign importance, facilitate memories, regulate alertness and modulate emotions. They interact continuously to manage multiple events of daily life.