The Neurological Causes of Stuttering

Biology 202
2001 Second Web Report
On Serendip

The Neurological Causes of Stuttering

Claire Walker

There are 55 million people all over the world who suffer from stuttering and about 3 million live in the Unites States. This disability has been misunderstood for hundreds of years, but it affects more men then women and it often runs in the family. People who stutter when they speak are sometimes considered to be slower, mentally, then people who can speak fluently. Although research has made some progress in diagnosing the causes of stuttering, people still have preconceptions about stutterers. There are new studies being done to find genetic and neural links to explain and perhaps help cure this potentially isolating disorder.

One of the problems that stutterers face in society is the fast pace that people talk. When trying to talk in public, people will often try and finish a sentence for someone who is stuttering. This seemingly harmless act can often cause the stuttering to be worse, because the person who stutters will be more conscious of the fact that they are talking slowly and they will try to speed up, only to trip and stumble on more words. This disability is interesting because it is not always present in a stutterers daily activities. It has been found that talking to pets, singing, acting and whispering often make the disability disappear (4). On the other hand when the person has to talk to someone of authority or try to impress someone, the stuttering becomes a severe speech block (3).

This dramatic variation in speech ability lead to the investigation of the causes of stuttering. People who stutter, obviously don’t lack the ability to talk fluently but rather have an interference in that ability (3). To find out if there was a neurological link in the brain that caused people to stutter, a PET imaging study was performed comparing stutterers’ brains and non-stutterers’ brains. This study showed that stutterers may be using the right hemisphere of their brain when they are talking, which means that the left hemisphere (the one usually responsible for speech) is being interrupted (4). Stutterers still complain that when they do have to talk, they feel a lot of nervousness and stress, but doctors are now starting to think that these feelings don’t start the stuttering but rather aggravate the problem (4). The interesting thing with the brain patterns is that they are present even when the stutterers aren’t talking. When the neural activation patterns of stutters and non-stutters during silent reading of single words were compared, it was shown that although both subjects had bilateral activation of the brain, the left hemisphere of the non-stutterers had more focus, while on the other hand the right hemisphere of the stutterers showed more focus (2). Similar results were seen when the subjects were talking. An interesting thing is that even treated stutterers, who have been in speech therapy and speak fluently, still have the same bias towards the right hemisphere, although some additional activation is present in the left hemisphere of the brain.

One part of this puzzle that interests scientists the most is the fact that 50-80% of all children who stutter, grow out of the disorder as they age. It seems that intervention with children makes it possible for the stuttering to disappear. For those children who continue to stutter into adulthood, it is seen in brain scans that the neural connections are different than in ‘normal’ adults (3). This suggests that if stuttering goes uncorrected in early age, the brain starts to ‘remember’ the stuttering and builds different neural pathways so that in the future those moments are remembered and the same words cause a stutterer to trip up. In the PET scans of the brain, the stutterers’ brains showed decreased activity in the auditory cortex and hyperactivity in the speech center while reading, which means that stutterer is actually tuning himself out when he is talking, so that he cannot hear the stammering (4).

One of the main problems with the study of the neurological causes of stuttering is that “... the neural system is the central driving force behind everything we think, feel and do,” so the “understanding of the etiology of stuttering will only emerge if we understand the neural bases of human behaviour (2).” Since everyone behaves differently and develops with their own experiences, the study of linking the brain to stuttering is extremely difficult. Why do children start to stutter? Some would say that is was because of an intellectually challenging upbringing which put stress on the child’s manner of speaking. But then again many children grow up in a similar environment and do not develop a stutter. There is no single cause that can be linked to why stuttering starts, so it is no good to study the input side of the nervous system. So to reach the anticipated output (stuttering), it is important to study the cognitive, linguistic, motor and other capacities of each stutterer (2). Such a study involves packaging all of the speech problems associated with the nervous system into a “fluency generating system (Watson & Freeman, 1997)”. This sort of study would try and find out what neural mechanism may lead to the development of stuttering in an individual (2).

One group of researchers found a connection between the functioning of the lateral and medial areas of the brain and stuttering. The lateral area of the brain controls the formation of words (Broca’s area), muscle movements (motor areas) and the understanding of language (Wernicke’s area) in what is know as closed-loop motor control (1). Using this area of the brain, stutterers can talk fluently, but they have to pay close attention to their speech, which as a result is slowed considerably (1). On the other hand, the medial area of the brain controls the open-loop motor control, which involves retrieving preprogrammed motor programs from memory and using them without feedback. This means that rapid speech can be produced with little effort, but since there is no error regulation stutterers will continually make the same mistakes in their speech pattern, especially when talking in a pressured situation (1).

So, stuttering has been linked to differing neural patterns, but why does stuttering cause different parts of the brain to be more active? One idea is called the Valsalva Mechanism, which is a natural bodily function, but it may turn the extra effort put into speech into the block that stutterers fight with everyday (3). The Valsalva Maneuver was named after an Italian anatomist, Anton Maria Valsalva and its purpose is to bring more air pressure into the lungs to help a person exert more force on an object, such as weight lifters who hold their breath when lifting large masses. (3). To create more air pressure in the lungs, the abdomen muscles contract and press against the diaphragm, which in turn presses up on the chest cavity. For this mechanism to increase the air pressure in the lungs, the larynx has to tighten around the airway so that the air cannot escape and this is called the effort closure (3). All of the muscles involved in the Valsalva mechanism are connected neurologically, so that they can all contract at the same time and with the same force (3).

The reason that this mechanism is thought to be tied to stuttering is because stutterers put a lot of force and effort into the words that they stumble over. This force causes the lips and tongue of the stutterer to press harder together, thus creating more air pressure in the lungs, but also causing speech difficulties (3). Fluent speech actually requires very little effort, so when a stutter puts a lot of effort into speaking the Valsalva Mechanism does what it is supposed to do, it is an instinctive reaction when we are trying to force something out of the body (3). This confusion between the Valsalva mechanism and the neurological components of speech can happen because there is neurological tuning involved in the motor neurons that control all the muscles involved in a movement, this includes speech (3).

What really happens during a stutterers speech is not wholly known, but if we take an example of someone stuttering on a word starting with p, say plane, then the brain remembers that p-words were difficult to say. Thus the brain ‘thinks’ that more effort has to be put into saying p-words, so the Valsalva mechanism kicks into gear and the stutterer is left squeezing their lips and trying to get any p-word to come out of their mouth (3). What makes p-words difficult for many stutterers is the fact that you have to close your lips, momentarily, to build up a little air pressure to say p-words. However if the nervous system is too excitable the brain may misinterpret this signal to mean that a Valsalva maneuver is being started and thus try and shut the air in the lungs, making speech very difficult (3).

This mechanism makes it extremely hard for stutterers to overcome their speech impediment, because even after they have gone to therapy and worked on slowing their speech, many stutterers relapse within a few weeks. Other treatments, such as electronic anti-stuttering devices, have been used with some optimistic results. Such devices allow the stutterer to listen to their own speech slowed down, which causes the use of the closed-loop system (1). Some researchers and doctors are hopeful that a drug treatment will be available for stutterers in the near future, because of the possibility of altering the way a stutterer’s brain functions. Genetic studies are also being carried out to see if a specific gene can be labeled as the cause of stuttering, in which case gene therapy would be an option.

WWW Sources

1)Neurology of Stuttering. Stuttering: Science, Therapy & Practice, A very interesting summary of the different hypotheses about the cause of stuttering. Offers some good clinical trials information.

2)Some thought on the multidimensional nature of stuttering from a neurophysiological perspective, A good place to find out some connections between Neurophysiological causes of stuttering.

3)The Valsalva Mechanism: A key to understanding and controlling stuttering, Made some interesting connections between a normal bodily mechanism and its connection to stuttering.

4)U.S. News & World Report (April 2, 2001, pp 44-51). Anatomy of a Stutter: New findings from brain studies and genetics are illuminating the causes of this ancient affliction. This article touched on some of the newest studies relating stuttering to the nervous system.

 

 

Continuing conversation (to contribute your own observations/thoughts, post a comment below)   09/25/2005, from a Reader on the Web i try very hard to not stutter, not sure why it happens more with some people, an not others im 50yrs and thought i had gotten over the fustration,, but it still happens,,, many has suggested things to do ,,, but they just dont understand... my thoughts are a lot faster, than my speech,i also try and choose my words carefuly,, in order to use less words,, to make the same point, when this i find that most people, dont pay close attention to what im saying,, so i find myself having to say it again some people i feel thinks im not intellegent,and lacks knowledge about things, thats not the case at all,but still im judged about my trurhfulness when trying to explain my views,, after 50 years im still having to deal with stigma thats comes with this disiability,,, i welcome any information that will help me, does this disiability qulifies a person social security. thanks for this place to vent... 11/23/2005, from a Reader on the Web I find it EXTREMELY fustrating for people to cut me off when im talking.I try so speak louder just to get my point across and it seems that EVERYBODY knows why I stutter.If it was that simple dont they think i would have "cured" it a long time ago.People dont know what its like to have to speak and nobody listens. That last comment i feel is really close to what I go through 11/30/2005, from a Reader on the Web Quite a bit has been written on the subject of stuttering and stammering. The notion that stutterers have lower IQ's is more prejudical than scientic fact. In my case, I have a MS is Education and Career Guidance. Stuttering in fact affects the general population more evenly and may suggest that those that do stutter may have higher IQ's rather than lower IQ's. Aristotle was said to have a severe speech defect and tried to "cure" the problem by putting small stones in his mouth and alter speech patterns. Whether this worked or not no one really knows. In my own case, I've stuttered since I started talking, and certain "triggers" set into motion abnormal speech. These triggers include, but are not limited to: excessive noise, cognizant words that I trip on, having a lucid fluid sentence with someone, only to have the listener say "huh,"and having someone be impatient or trying to finish thought. Chances are the repeating the sentence is more of frustration of having someone not listen nor pay attention to what I may be saying. In this way, I may reason that what I may be saying is really not important and self-esteem then becomes an issue. While speaking in front of a large gathering of people frightens most stutterers, I have little problem standing on a dais lecturing or reciting a written passage to peers or strangers. Learned behavior and breathing patterns are probably the two big culprits, and I have noticed that in my case, I try to speak without taking a breath. Try this: let all the air of your lungs, then try to speak! This can't be done. In a program run by the University of Southern California in the 1970's, controlled speech therapy by having the subject speak more slower and have the air flow through the larynx by exaggerating longer sounds. There have been many therapies and while a lot of these work, some are better than others depending on the stutterer.

 

 

Im 14 and I studder. It's really hard for me right now . I can't even raise my hand in class and It's effecting my grades bacause I know If I could talk I could do better. I can barely have a conversation with my friends and my family annoy's me bacause they tell me to slow don tap my leg and it dont help they dont know what it's like not being able to talk on the phone. My mom looked into a ear piece called the fluency master. I was getting all exited but it's been a year. I dont think she's relly tried her hardest. why did she have to put that in my head well I have to go ... Cody, 10 May 2006

 

 

I am 41 years old and I have stuttered all but the last two years of my life. I have a device called a fluency master and it has dramatically cut down on my stuttering. I use to always hate it when someone would finish my sentences for me, or laugh at me. We are not dumb and we are not uncordinated. Over the course of my life I have had some nasty things said to me. Everyone who stutters can say that. If you saw two co workers looking at you and then each other and then laugh, what would you think they are laughing about? Peple can be so ignorant. Stuttering is something that is so misunderstood. I had a great grandfather on my fathers side that stuttered some and my uncle on Moms side stutters severely. This disorder makes you think you are substandard as a person ... Carl Jenkins, 27 May 2006

 

 

I have been stuttering all of my life, so did my brother. people have teased and made to look stupid for most of that life. I had to learn the hard way that they were the ones that were spudid not me. I have accepted the fact that i will stutter for the rest of my life so why not embress it , since it is a part of me. if you accept me as a friend or loved one uoy will have to accept the stuttering too ... Phillip Sloan, 23 August 2006

 

 

Come from a family of late bedwetters and also stutters. Have partical seizures, take gabapentin daily. Suddenly find that I really don't stutter.Thought I'd share this with you. Also note that one the during the times when I think that I am going to stutter; I find an abnormality in my breathing process. For me there are or rather where many types of stuttering. One where I have so much to say that the words trip over each other as I can't say evrything at once. Two; when I am so nervous that I can't even say "Hello' on thre telepone. Or three; just can't say what I want to. Oh, but I sing very well ... Kathleen Edsall, 21 October 2006

 

 

By the age of 24 I earned the equivalent of a masters degree in stuttering. No one could stutter more often that I.

I was shy, lonely, anti social, and neurotic.

I began to keep a written record of every frustrating incident in my life. I always concluded these written comments with a self administerd pat on my back to invigorate, my then, non existant, self esteem.

After numerous entries I began to realize the my stutteing was related to my self esteem. When I attempted to avoid noting my frustrations, my stuttering resumed. When I resumed my notations, the stutteing disappeared.

I believe that, by my 26th year, I have had no recureence of stutteing. I lost my shyness, my neurosies and my low self esteem. I am 80 years old now. No one believes that I was once a stutterere ... Julius Silverman, 30 November 2006

 

 

For over the past year or so, i cant really pin point when i first noticed my inability to get things out as fast as my brain was thinking. Or picking and choicing words or phrases that i can get out with less of a pause or stuttering. I dont show signs of it all the time, but enough to where it affects my relationships with my friends and my ability to go out and meet new people. Now my questions is related to drugs and can they cause stuttering. I ask this because when i first started using i showed no signs of a stutter/speech problem. This was a lil more then 3 years ago, now for a year or so i think my inability to say what i want it pissing me off. So any information regarding drugs use causing stuttering or stressful environments causing this...Anything from anyone regarding this would be great ... Taylor, 2 March 2007

 

 

When I speak, i sometimes feel the lack of confidence thats why i stutter...but when i feel ok and confident, i can speak real good and clear...i have a scar on my face thats why i became conscious of my environment that i felt all people are focused on me when i speak...i feel that they are looking at my scar thats why i feel nervous and shy--it makes me stutter...im a good singer and i won singing contests...i play piano...i paint...i cook...i write poems, essays, songs...im very good at it....i won several awards and recognitions for my talent and creativeness...i have an IQ of 126 (highly intelligent)...its just that im lacking of self confidence that i stutter when im nervous or shy...i think a healthy diet and lifestyle, a good family relation and communication will help alot to people like us who stutter ... Kurt, 16 March 2007

 

 

With all the speech therapy that could be crammed into me from as far back as I can remember, and probably much longer, for the first 32 years of my life I existed in the increasingly self-limiting spirit- breaking world stutterers grudging get used to. Of course, I did receive a ray of hope when I last saw my therapist of 2 years at the end of 6th grade and we agreed that I should expect a fluency rate of 60%.

Well, 20 years later, I walked into the office of a doctor for another matter entirely and he prescribed some pills. I took them that night and by maybe the next day or two, I no longer stuttered. And 26 years later I still haven't, except for the time when another doctor briefly took me off the anti-seizure medicine (Tegretol) I had been put on.

I hope stutterers will be given a basic neurological exam or, simply, tried out on an anti-seizure medication to see if it might help. Some may even be "cured" and allowed to live a fullfilling, well rounded life ... Jonathan Kleid, 29 May 2007

 

 

I stuttered so bad all the way up until my late teens that I had to write down what I was going to say before I made a phone call. Often people would hang up on me before I could get through a sentence. I almost failed every grade, and always thought I was stupid as so I was treated, even by my family.

I also had terrible acne and because we moved a lot I was usually the new weird looking kid who was easy to pick on. I made humor of my stuttering to win friends and to keep safe even if they were laughing more often at me than with me.

I moved out while we were living in Huntsville,Alabama as I was almost 18 and wanted to finish high school with my new friends I had made, rather than move to Ohio and have to start all over again. I also had my first girlfriend, Clair. I could fake playing the guitar and found that I did not stutter when I sang, and my girl loved to sing harmony.

A little more than a year prior to this I was living in Bay St Louis, Mississippi and use to hitch hike quite a bit as I liked meeting strangers and pretending that I was somebody else.

While hitching one day I met a most lovely and deeply southern couple. They were in their late forties and were recently married. After a short while riding and chatting from the back seat up to the two of them, the lady turned to me a said "You stutter don't you?" "Well I'm going to tell you the same thing I told my last husband who also stuttered, this one is my third." she interrupted her preaching with a big gleaming smile as she patted her husbands shoulder.and then continued her sermon. "When you find somebody who you can believe really loves you, you will stop stuttering." The words meant something to me but I would not fully digested their meaning for years to come.

Back to Alabama, may be six months after my parents moved I got kicked out of school because they found out I was living alone while working as a janitor to pay my rent. This gave me a lot more time to confront my relationship with myself.

I tested Clair in every way to prove she did not love me. For many years before Clair I had pretended to be somebody new with almost every group of people I had ever met and had so many lies about me I could not remember all that was true. I exposed all that I could of this to her and still she wanted me. As my esteem grew I tested her in worse ways like fooling around with casual friends. We almost made it to the other side of my testing but she too injured to recover finally dumped me, just as I began to understand that she had truly loved ME.

The point of the story is that the more present I became and spontaneously honest the less I stuttered. I stopped stuttering for the most part by the time I was 19. Presently 54, I am happily married for three years to my first wife, am a municipal Judge, a therapist for twenty something years, and a portrait painter.

Consciously finding oneself connected beyond reason (another way to say finding LOVE), is always good therapy and perhaps a cure for many cases of stuttering ... Grant Freeman, 20 August 2007

 

 

i have a stuttering problem which has stuck by me since i was in the first grade. it was hard at first because i couldnt barely get my words and the kids at school would pick and mock me. i used to cry to my mom about it because i felt different from the other kids. she thought it was something temporarily but it wasnt. still to this very day, i have a stuttering problem. no body really picks on me about it because its very unnoticeable. i try my best not to stammer or mess up when i'm speaking but i get really anxious and excited and i just go away with it. my family jumps down my throat about me taking my time because they want to understand what i be saying sometimes but i can't help it. my fiance barely knows it because when i'm around him, i don't stutter. but if i'm around alot of people or with someone i don't know, then i will definitly stutter. as a new mom, i question myself rather or not my little girl will stutter or if i can prevent that from happening ... Porsche McGill, 3 November 2007