Neurology of ADHD
ADHD Brain: The Neurology of Inattention, Impulsivity, and Hyperactivity
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.
- 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?
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.
If you are researching the topic of the NEUROLOGY OF ADHD these books would be good resources for you to get and read.
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.
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 brainstem reticular formation runs all the way up to the mid-brain. As a result, 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. ADD ADHD Reticular Activating System Neurology
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.
More Neural Connections Needed
However, it is not just activation levels of the Reticular Activating System that are a problem with Attention Deficit individuals.
It seems that the same problems that cause the Reticular Activating System to be under or over aroused also restricts the development of neural connections and the required neural density needed to process incoming information.
In other words, these are issues with the number of brain cells, the size of the brain cells, and the number of connections between brain cells. It is not uncommon for one brain cell to have as many as 5,000 connections with other brain cells.
Picture the incoming information to be processed and learned as the volume of water coming out of your shower head. And picture the brain's ability to process this information as the drain and the drain pipe in the shower floor. If the pipe is clogged up, your shower will have problems draining. If the contractor originally installed a drain pipe that is too small, again your shower will have problems draining. In either case, you will either have to reduce the amount of water coming out of the shower head, or you will have to let the shower back up and wait a while for the water to finally drain out. Here’s the connection…
If the brain does not have enough neural connections, or lacks the neural density, to process the incoming information, then it will be like a pipe that is too small to handle a large volume of water. It will take in some, but the rest will be stopped and won't go down the pipe rapidly. Learning will take place, but the time that it takes to process the information will be slowed significantly.
The impact of this with an Attention Deficit Hyperactivity Disorder child is best seen when the child is given a timed test, even with material that the child understands pretty well.
The "timed" aspect of the test requires that the child have a “larger drain pipe,” as it were, to quickly process the problems on the test and recall the answer. However, with ADHD the “pipe” is often too small, and the results of the timed test will probably be very poor.
However, take away the timed element on the same test, and “allow the water to drain a the slower rate,” and the child will probably do well on the test.
So the ADHD child, or adult, needs a greater degree of neural density, and a larger number of neural connections to process information faster and more efficiently.
Now, please do not think that this information to be processed is only what takes place in the classroom.
The information to be processed includes information from the outside world, including the touch of the clothes on his skin, the buzz of the lights overhead, the sound of the kids playing outside, and the new information that the teacher is lecturing on at the front of the classroom.
It also includes the information from inside the head, the thoughts and feelings of the ADHD person.
All of that must be sorted out and filtered, so that only the important information is paid attention to, and the unimportant information is ignored. Without proper filtering by the Reticular Activating System, the individual will be distracted by "noise," both from outside of him as well as from inside of him.
ADHD Causes
The most recent 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 elsewhere.
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: (1) either doing or saying something without thinking first; or (2) not saying “no” to yourself, inhibiting yourself, when you ought to do so.
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."
Vanderbilt psychologists Leanne Boucher, Thomas Palmeri, Gordon Logan and Schall published the findings in the April issue of Psychological Review.
The new paper uses physiological data collected in Schall's laboratory to show how a theoretical model Logan developed more than 20 years ago is implemented by the brain.
"I developed the race model to explain behavior on a task called the stop signal task with a friend of mine, William Cowan, who is a theoretical physicist, in the 1980s," Logan, Centennial Professor of Psychology, said. Stop signal tasks measure an individual's ability to stop a planned action, like pressing a key on a keyboard or looking at a target, in response to a signal. "Our race model proposed that two independent processes were underway, one telling us to 'go' and one telling us to 'stop' in response to the stop signal.
"Applying the model to children's behavior revealed that stop signal task times are significantly longer in children with attention deficit and hyperactivity disorders than in other children," he said.
In this model, "go" and "stop" processes independently race one another - whichever one crosses the finish line first determines whether a movement is made or not. Though the model accurately explains behavior, it left neuroscientists scratching their heads. Their work found that 'go' and 'stop' processes are produced through a complex network of interacting neurons. If so, then how could 'go' and 'stop' be acting independently as required by the race model?
"The model proposes that there are two processes happening in our brain, one making us 'go' and another making us 'stop'," Boucher, a postdoctoral fellow, said. "However, as neurophysiologists, we know these processes are intricately linked, not independent.”
The findings are some of the first to bridge cognitive research and neurophysiology - making the connection between the mind and the brain.
For more information about this study visit the Vanderbilt website.
Press Release by Melanie Moran