Neurology of ADHD
ADHD Brain
What is Happening in the Brain of a Person with ADHD ?
The most recent models describing what is happening neurologically in the brains of people with Attention Deficit Disorder suggest that several areas of the brain may be affected by the disorder.
They include:
- Frontal Lobes
- Inhibitory Mechanisms of the Cortex
- Limbic System
- Reticular Activating System
- What causes these various systems of the brain to get out of balance with Attention Deficit Hyperactivity Disorder individuals?
- Why would these systems become under aroused or over aroused?
- Is there one central system that controls or regulates these other systems?
- either doing or saying something without thinking first; or
- not saying “no” to yourself, inhibiting yourself, when you ought to do so.
Each of these areas of the brain is associated with various functions of the brain.
Above is a sample Q-EEGs of two Attention Deficit Disorder children compared to two non- ADD ADHD children.
The Attention Deficit Disorder children show excessive slow brainwave activity (theta and alpha ranges) compared to non- ADD ADHD activity. The slow brainwave activity indicates a lack of control in the cortex of the brain.
"Lack of control" is pretty descriptive of Attention Deficit Disorder kids. Medications, EEG Biofeedback training, Attend Nutraceuticals, and some other interventions, seem to change this and normalize, at least temporarily.
Impulsivity, Hyperactivity, and Lack of Inhibition
The frontal lobes help us to pay attention to tasks, focus concentration, make good decisions, plan ahead, learn and remember what we have learned. The frontal lobes also help us to behave appropriately for a given situation.
The inhibitory mechanisms of the cortex keep us from being hyperactive, from saying things out of turn, and from getting mad at inappropriate times, for examples. These inhibitory mechanisms of the cortex help us to "inhibit" our behaviors.
It has been said that 70% of the brain is there to inhibit the other 30% of the brain.
When the inhibitory mechanisms of the brain aren't working as efficiently as they ought , then we can see results of what are sometimes called "dis-inhibition disorders" such as impulsive behaviors, quick temper, poor decision making, hyperactivity, and so on.
The limbic system is the base of our emotions and our highly vigilant look-out tower.
If the limbic system is over-activated, a person might have wide mood swings, or quick temper outbursts. He might also be "over-aroused," quick to startle, touching everything around him, hyper-vigilant.
A normally functioning limbic system would provide for normal emotional changes, normal levels of energy, normal sleep routines, and normal levels of coping with stress. A dysfunctional limbic system results in problems with those areas.
Attention Deficit Disorder might affect one, two, or all three of these areas, resulting in several different "styles" or "profiles" of children (and adults) with Attention Deficit Disorder.
Reticular Activating System and ADHD
Attention Deficit Disorder and the Reticular Activating System
The answer may be found with the Reticular Activating System.
The Attention Center
The Reticular Activating System is the attention center in the brain. It is the key to "turning on your brain," and also seems to be the center of motivation.
The Reticular Activating System is connected at its base to the spinal cord where it receives information projected directly from the ascending sensory tracts. The brain stem reticular formation runs all the way up to the mid-brain.
The Reticular Activating System is a very complex collection of neurons that serve as a point of convergence for signals from the external world and from interior environment. In other words, it is the part of your brain where the world outside of you, and your thoughts and feelings from "inside" of you, meet.
This Reticular Activating System is very capable of generating dynamic effects on the activity of the cortex, including the frontal lobes, and the motor activity centers of the brain.
The Reticular Activating System and Learning
The Reticular Activating System plays a significant role in determining whether a person can learn and remember things well or not, on whether or not a person is impulsive or self-controlled, on whether or not a person has high or low motor activity levels, and on whether or not a person is highly motivated or bored easily.
The RAS is the center of balance for the other systems involved in learning, self-control or inhibition, and motivation. When functioning normally, it provides the neural connections that are needed for the processing and learning of information, and the ability to pay attention to the correct task.
If the Reticular Activating System doesn't excite the neurons of the cortex as much as it ought to, then we see the results of an under-aroused cortex, such as difficulty learning, poor memory, little self-control, and so on. In fact, if the Reticular Activating System failed to activate the cortex at all one would see a lack of consciousness or even coma.
What would happen if the Reticular Activating System was too excited, and aroused the cortex or other systems of the brain too much?
Then we would see individuals with excessive startle responses, hyper-vigilance, touching everything, talking too much, restless, and hyperactive.
So the Reticular Activating System must be activated to normal levels for the rest of the brain to function as it should.
What factors could cause the Reticular Activating System to be either over-activated or under-activated?
According to Harvard Medical School, current research strongly suggests that Attention Deficit Disorder – ADHD is caused in part by a deficiency of Norepinephrine in the ascending reticular activating system.
It is thought that the stimulant medications, such as Ritalin, increase the levels of Norepinephrine in that part of the brain, as well as probably increasing dopamine levels in the frontal lobes.
This treatment strategy works well for the inattentive under-aroused ADHD kids, and somewhat well for the over-aroused impulsive-hyperactive ADHD kids.
However, for the kids who have an over-aroused Reticular Activating System to begin with, the use of stimulants will often exacerbate the problems with temper, sleep, and hyper-vigilance or anxiety.
For these individuals their physicians will often prescribe a Norepinepherine antagonist such as Clonadine, or an antidepressant such as Prozac, which works to enhance the Serotonin driven inhibitory mechanisms of the brain.
See the Reticular Activating System to learn more
ADHD Causes
Some models that attempt to describe what is happening in the brains of people with Attention Deficit Hyperactivity Disorder suggest that several areas of the brain may be affected by the disorder. They include the frontal lobes, the inhibitory mechanisms of the cortex, the limbic system, and the reticular activating system. Each of these areas of the brain is associated with various functions.
There are several areas of the brain potentially impacted, and there are several possible "types" of ADHD. Daniel Amen, a medical doctor using SPECT scans as identified six different types of ADHD, each with its own set of problems, and each different from the other "types."
In our practice we used five different "types" of ADHD, identifying each "type" with a character from the Winnie the Pooh stories (Pooh is inattentive, Tigger is hyperactive, Eeyore is depressive, and so on). We discuss in greater detail in the different types of ADHD section.
The frontal lobes help us to pay attention to tasks, focus concentration, make good decisions, plan ahead, learn and remember what we have learned, and behave appropriately for the situation.
The inhibitory mechanisms of the cortex keep us from being hyperactive, from saying things out of turn, and from getting mad at inappropriate times, for examples. They help us to "inhibit" our behaviors.
It has been said that 70% of the brain is there to inhibit the other 30%.
The limbic system is the base of our emotions and our highly vigilant look-out tower. If over-activated, a person might have wide mood swings, or quick temper outbursts. He might also be "over-aroused," quick to startle, touching everything around him, hyper-vigilant.
A normally functioning limbic system would provide for normal emotional changes, normal levels of energy, normal sleep routines, and normal levels of coping with stress. A dysfunctional limbic system results in problems with those areas.
The Attention Deficit Hyperactivity Disorder might affect one, two, or all three of these areas, resulting in several different "styles" or "profiles" of children (and adults) with ADD ADHD.
Neurology of Attention Deficit Hyperactivity Disorder.
Impulsivity - Go and Stop in the ADHD Brain
New Research Offers Insight Into Cause Of Impulsivity in ADHD
We have often felt sorry for those impulsive children who blurt out the first thing that comes to their mind when asked a question, especially if they are about to get into trouble. As most parents know, that first thing that comes out as the answer is usually a lie. And then the child has to spend the rest of the hour covering up the lie, that both he and his parents know is a lie. This is a classic scene of a child with ADHD getting into trouble because of his impulsivity.
As a remedy, we encourage parents to warn the child that they are about to be asked a very serious question, and that their honesty is absolutely required. And that the child is not to answer the question for 30 seconds after being asked, so that they can clearly think about what they want to answer and get it right the first time. This works. But it is not what this article is about...
Impulsivity in ADHD
Impulsivity in ADHD is seen in two ways:
It seems that a person with impulsivity as a part of their ADHD has a normal ability to say “Go” at the neurological level, but their ability to say “No” or “Stop” comes just a fraction of a second slower. As a result, things are often done, or said, without much self-control practiced.
Vanderbilt Research on ADHD
There is some very interesting new research out of Vanderbilt University’s Center for Integrative and Cognitive Neuroscience that helps to explain impulsivity in ADHD. From their press release, here are the basics of the study:
"We think of people who are impulsive as acting too quickly," said Gordon Logan, one of the researchers. "Kids with ADHD are actually slower on the 'go' task than the control kids. It's not that they go too quickly; they stop too slowly."
"The research provides new insights into how the brain controls movements, which helps explain the impulsivity of people with attention deficit and hyperactivity disorder," according to study co-author Jeffrey Schall, E. Bronson Professor of Neuroscience. "It also shows how mathematical models can be used to discover how the brain produces thought and action."
Read about the new Vanderbilt Study on Impulsivity
See our collection of ADHD Research articles, or read the articles below to learn more about the ADHD brain and the neurology of attention deficit hyperactivity disorder.
