A New Look at Auditory Stimulation

The Institutes have know for decades that certain brain injuries cause hyperactive auditory sensitivity. More recently others have also begun to study this problem. I first became aware of that condition when I met David, an eight-year-old brain-injured child at The Institutes who had this problem. He screamed at the slightest noise. In fact, he screamed eight hours a day. His parents whispered all day to keep from setting him off.

When they arrived at The Institutes David was given the auditory stimulation program as part of his overall program. His parents were instructed to bang pots and pans randomly around the house! David's mother told me she laughed all the way home after that initial visit. However, they did The Institutes auditory stimulation program and within two weeks David was no longer hypersensitive to sound.

Posterior cortical midbrain-injured children (those children commonly labeled "autistic") are known to have dramatic auditory hypersensitivity. Some report being able to hear water running in the pipes underground and the beating of people's hearts. Others display obvious pain at the slightest sound and cover their ears if someone touches their hair.

Rub inside your ear canals with your fingers and you might get a small sampling of the kind of sound that would be experienced when someone gently puts his hand on the head of such a brain-injured child. If you do it while someone is trying to speak to you, you will find you are functionally deaf and unable to follow what is being said.

The Institutes received a machine called an Audiokinetron, which was designed by Dr. Guy Bérard to treat brain-injured children using music as a kind of stimulus. Parents have been reporting positive changes occurring in their children after treatment with the Audiokinetron. Some parents have observed a marked decrease in their child's sensitivity to sounds, decreased screaming, decreased hyperactivity, less tendency to have temper tantrums, deeper and better quality sleeping, increased attention, interest in their surroundings, and improved language. Some of the children have shown affection for their family and friends for the first time in their lives.

The creators of the device believed that the machine exercised and trained the muscles in the ear. "Earobics" they called it. Further, they described sound as "nerve food" or a source of energy for the body. They also ascribed a kind of intelligence to the ear muscles.

The changes in the children were undeniable and they were important changes. The children themselves reported that the auditory stimulation helped them by making their lives easier and more enjoyable. However, as we studied the device and the results of treatment we began to formulate a completely different view of how and why the machine worked.

Since brain injury is in the brain and not the ear, we knew that these children's problems were not in their ears any more than a midbrain-injured child's problem is in his legs.

The study of psycho-acoustics is helpful in defining the links between a healthy auditory pathway and the brain-injured child's auditory pathway. Unlike the eyes, which can be shut when looking into the sun, the brain has little mechanical ability to limit over stimulation. However, the brain does have the capability to affect and manipulate incoming auditory stimulation.

The brain has the ability to rest from auditory stimulation simply by ignoring it. The brain has the ability to "normalize" auditory stimulation. When we first turn on a transistor radio the sound is awful. No low frequencies, no high frequencies, and very low fidelity. But we quickly become "accustomed" to it and it no longer sounds "bad" or "wrong".

Another psycho-acoustic ability is called the "cocktail party effect". Someone can be talking to a person in a large crowd when suddenly another voice catches his attention. If the new voice or subject is interesting enough, a person can tune out the person in front of him who is producing the loudest acoustic wave form and focus on the much softer auditory stimulation from across the room. This function is a filter, but one of astonishing complexity. In order for a system (the brain) to be able to filter out higher volume stimulus of a similar frequency to lower volume stimulus, the system must be able to predict the behavior of both sets of stimulus simultaneously. Speech pattern recognition is fundamental to this activity.

Analog to digital encoding schemes used in digital audio systems are designed around the brain's ability to "fill in the missing information" thereby allowing the converter to throw away audio data and compress the bit stream. The smaller bit stream allows more information to be stored in less disk space.

The brain has the ability to normalize and remember acoustic environments. When a person first enters a very loud room he is accosted by the sound, his adrenaline levels rise, and his ears hurt. But after a few minutes his hearing changes to accommodate or "normalize" the environment. This is not so much his tensor muscle tightening but his brain making sense of the noise in the room. In fact, the next time that person enters the room it will not be so uncomfortable. Speech recognition will be easier and the sense of "loudness induced confusion" will be less.

My wife and I have four boys who can make a real racket when they want to. Our last house had a large ambient kitchen. The boys were so loud in it that I wondered whether I could even live in the house. Within a couple of weeks the room didn't bother me at all. The blind singer Stevie Wonder is reported to have a legendary ability to snap his fingers when first entering a room and from the echoes learn and remember its boundaries.

The brain has the ability to differentiate between direct and reflected sound. The difference between the perceived sound in a room and the sound recorded by an omni directional microphone is dramatic. The microphone always sounds more reverberant and hollow. I could never record a symphony from the balcony, because the orchestra would sound too far away. But it can be a very satisfying musical experience from there, especially if the listener can see the orchestra.

So far we have seen psycho-acoustic effects in well systems range from manipulation to mild defense, but let's look at the severely distorted system in the brain-injured child. Because of his brain-injured auditory pathway, certain sounds scream at him like a runaway locomotive's brakes, overwhelming him.

We have seen that the brain can manipulate auditory stimulation and does so routinely. When a hurt child experiences uncomfortably high sound pressure levels, his brain goes through a series of self-protective steps. The first step is like the "cocktail party effect," selective listening. The second is compression, the ability to reduce or try to control the effect of loud auditory stimulation. The third level of self-defense may be called suppression.

This is stimulus-induced deafness.

Some brain-injured children live in a world of chaos caused by the bombardment of auditory stimulation. Their brains are in a state of sensory defensiveness, suppressing or distorting all input.

Why does the Audiokinetron work? System response time delay.

All systems, whether mechanical or biological, have a finite duration of time between the command to action and the response. In electronic devices, this time is the speed of light. In mechanical systems, response time is a function of efficiency of motion. In biological systems, response time is widely variable and dependent on a host of factors - restedness, nutrition, alertness and most importantly wellness.

Glenn Doman has described the time delay experienced by stroke victims that makes it almost impossible for them to do something as fundamental as answer a simple question, even when they know the answer! Because of system response time delay, by the time the victim has mustered a response to the question, the person asking the question has left or moved on to another question. As a graduate of the How To Multiply Your Baby's Intelligence Course, I have been taught to be patient and wait for my baby to respond to my attention, allowing time for his newly developing brain to affect a response.

Brain-injured children do not have a well system, therefore their system response time is delayed. When one combines auditory hypersensitivity with a delayed response time, a picture emerges. Only a signal sufficiently long enough to exceed the response time of the system will elicit a defense mechanism.

The Audiokinetron is a two-stage device. The first stage is a simple cuts-only graphic equalizer that is designed to lower certain sound frequencies by forty decibels. This allows the stimulus music to be contoured to the particular patient's hearing.

The second stage functions by taking music and creating from it a series of powerful, short-duration, random, high-frequency pulses. As the child listens to the music, he is attacked by the accompanying pulses. His hypersensitivity causes his brain to react, but by the time his brain overcomes the time delay the pulse is gone. The brain no longer has anything to defend against, so it relaxes. Eventually the brain learns it is futile to either try to predict or respond to the short-duration stimulus. Hyperactivity starts to diminish, and the child begins to emerge from below.

A therapy that I call Transient Electronic Auditory Stimulation (TEAS), is electronic pots and pans. The music is there to entice and relax the child, and the stimulus is unpredictable and short-duration. Consequently the brain can't defend against it.

How can we become more successful using this information to treat brain-injured children who have these kinds of auditory problems?

Our first goal is to improve therapy procedures using existing or available equipment.

What are the biggest problems facing us in this goal? First and foremost, analysis.

Brain-injured children have severe problems communicating with the outside world. The standard audiology exam requires skill in listening, concentration, and sophisticated communication. Furthermore, it is only designed to be effective within a normal to low sensitivity hearing range, because it is designed to reveal hyposensitivity or loss, not hypersensitivity.

We need a way to perform an active, non-invasive, safe, highly accurate, high-resolution frequency analysis of the auditory pathways of all brain-injured children.

We began investigating the "evoked potential" method of audiology about a year ago. Evoked potentials are electrical signals evoked within the brain by exterior stimulus. This technology seemed promising at first, but a number of things made it inappropriate for our work. We could not find a system that was more than a simple pass-fail test. This gave us none of the specific frequency sensitivity that we needed to use the Audiokinetron properly. Second, we were told that uncooperative patients needed to be sedated for the test. That was the end of that.

Ten years ago it was reported that high-frequency whistling could be heard coming from the ears of cats. As a result it was thought that our auditory system was not, as we believed, a passive system receiving stimulus in the form of sound waves, but was instead an active system somewhat like an AM or FM radio station. Sound waves generated by nerve endings in the middle ear are transmitted to the outer ear, where they are modulated by external sound sources and are then reabsorbed by the eardrum. The carrier wave is stripped away from that signal neurologically and the resultant signal is what we perceive as sound.

These whistles are now called autoacoustic emissions.

Whether the original theory is correct or not is somewhat irrelevant to our needs. Autoacoustic emissions seemed to promise a new insight to the function of the neuro-auditory system. However, when we first discussed this with the manufacturer they told us that autoacoustic emissions were only a resonance of the nerves in the inner ear. But I was sure that autoacoustic emissions were a result of active control from the hearing center in the brain. Consultation with Glenn Doman confirmed that there are more nerve pathways from the brain to the ear than from the ear to the brain. Once again we found ourselves on the other side of the fence from a manufacturer's theory of the operation of his own machine.

Supporting our view is a just-released study by the Mayo Clinic that confirms the efferent action on autoacoustic emissions through the neural pathway from the brain. We were relieved to learn of this report. Without this confirmation, autoacoustic emissions analysis could have been another expensive dead end. Now we may have a powerful tool to accurately analyze the hearing of a brain-injured child.

A young man named Gabe volunteered to be tested by the Virtual 330 autoacoustic emissions system. Gabe is extremely hypersensitive to many sounds and is receiving Transient Electronic Auditory Stimulation at The Institutes. On his first test on the machine Gabe exhibited a narrow-band hypersensitive spike of forty to fifty decibels at 4KHZ. When the spike literally jumped off the computer monitor's display, I turned to Glenn and said, "There it is! That's what we've been looking for!" The audiologist who was demonstrating the machine turned to me wide-eyed and said, "I have never seen anything like that in my life!" This was the first time he had tested a brain-injured child with the machine.

We continued to test Gabe, but it was soon obvious that he was in abject pain every time the machine's test frequency approached 4KHZ. He would start to create noises and writhe but continued with the test because he knew he was helping us with something important. We took a break and Gabe typed a message to his mother that he had to block the sound because it was painful! So we stopped the test.

Later we set up the machine again in order to do a demonstration for the staff and the board of directors. While Dr. Ralph Pelligra was being tested, I noticed the computer was running much more quickly and with higher resolution. I asked the audiologist what was going on and he told me he was now using a much shorter duration test pulse and taking far fewer samples per frequency. That day even our failures had supported the theory. The test signal that we used for Gabe was of a much longer duration than that for Ralph - just long enough to elicit a defense response from Gabe's brain, except for the first time when it was a surprise. Because the tones used by the machine are sine waves progressing evenly from low to high frequency, Gabe was able to predict the tones after the first test. He even told us so.

The optimum instrument parameters for testing brain-injured children should be:

1. Shortest duration pulse.
2. Smallest number of samples needed to get a result.
3. Lowest amplitude signal, so as not to present a painful stimulus to the patient.

We learned something else that day. Even a test that is benign to most children, even preemies, can be injurious to brain-injured children unless the test parameters are contoured specifically for them. Since that time there has been a published study citing the discovery of a 4KHZ hyperactive anomaly in some brain-injured children using autoacoustic emissions analysis techniques.

During a board meeting after this test the entire clinical staff discussed this issue and decided that if the children were to wear earplugs that the level of unwanted auditory stimulation would drop and their condition should improve. This alone would not be an acceptable therapy, only a crutch that would not be self-eliminating. However, if we had the kids wear the ear plugs before TEAS, their chemical wall of defense should be at low levels and therefore TEAS should be more effective. The staff started with the earplugs, and the response from the children and their families was immediately positive. By improving the effectiveness of TEAS the plugs are self-eliminating.

The next step is to improve the TEAS machine itself. Right now the machines are like shotguns shooting at a bull's-eye on the wall, because the stimulation signal is fairly broadband. Without extremely accurate audiology exams this is the only way to be effective. In fact, the staff have so little faith in the conventional audiology exams that they are not even using the multi-band filter stage of the Audiokinetron. However with more accurate autoacoustic emissions analysis we can start to use the machines more effectively. Secondly, we can begin the design of a second generation of machines that focus directly on the hypersensitive frequencies of the child, making the therapy more comfortable and effective.

The Institutes for the Achievement of Human Potential have been successfully administering auditory stimulation for many decades. I hope our forays into the technological side of this subject can lead to more understanding of the problem and so further the successful treatment of brain-injured children.

by William Mueller