Speech-Language Pathology/Stuttering/Speech Motor Learning and Control/Biofeedback

Feedback and Biofeedback

The associative stage of motor learning requires feedback. In sports this is called knowledge of results. E.g., in golf or tennis you see where the ball goes after you hit it. Playing golf or tennis on a dark, foggy night would be impossible.

Feedback quality is affected by speed. If you hit ten golf balls on a dark, foggy night, then the next day find one of the balls 150 yards away, you'll have no memory of what you did right to hit it so far.

Feedback quality is also affected by accuracy. If you and your buddy each hit a golf ball, and one ball goes 150 yards but you don't know whose ball it was, you have inaccurate feedback.

Or the observer gets bored. If you hit golf balls for hours, and have a person telling you how far the balls go, sooner or later the person will stop paying attention.

Fluency Skills Feedback

When you're learning fluent speech motor skills, you need knowledge of results. Some skills are easy to observe the results of. E.g., resting your hand on your stomach tells you whether you're using diaphragmatic (relaxed) breathing or thoracic (speech) breathing.

Your articulators (lips, jaw, and tongue) are a little harder to be aware of, as you can't see them. But you have good proprioceptive awareness of these muscles, so developing awareness and control isn't hard.

Your vocal folds are another story. These muscles are deep in your throat. You can't touch them or see them. Most people don't even know they have vocal folds.

The most difficult feedback is with the timing of all this. E.g., your speech-language pathologist tells you to exhale a little air and then increase your vocal fold tension. You do this slowly and correctly. Then she tells you to increase the speed. You must execute these movements within hundredths of a second. You can't tell whether you're doing it right, and most speech-language pathologists can't either.

A fluency specialist who's helped hundreds of stutterers has better-trained ear and visual skills and gives better quality of feedback than a speech-language pathologist who's never treated a stutterer.

Biofeedback Devices

In the last chapter I discussed anti-stuttering devices that treat the auditory processing underactivity associated with stuttering. Now I'll discuss stuttering therapy devices that use biofeedback to treat the speech motor control overactivity associated with stuttering.  *   

Biofeedback is the measurement and display (to the user) of a physiological activity, to enable the user to improve awareness and control of the activity.

Biofeedback machines provides faster, more precise, and more reliable feedback than a human observer. Machines can provide feedback in real-time, beeping the instant you make a mistake. Machines can accurately measure things humans can't see or hear. And machines never get bored, even after hours of practice.

But biofeedback devices aren't a &quot;miracle cure&quot; for stuttering. Stuttering therapy works on many motor skills, so you might need several devices. Another problem is that certain motor activities are difficult to monitor, especially the vocal folds.

CAFET and Dr. Fluency

The Computer-Aided Fluency Establishment and Trainer(CAFET) and Dr. Fluency are computer-based stuttering biofeedback systems. Both use a microphone to monitor vocal volume, as a surrogate for vocal fold activity, and a chest strap to monitor breathing. Dr. Fluency uses two chest straps, to differentiate diaphragmatic (relaxed) breathing from thoracic (upper chest) breathing.

You see your breathing and your vocal volume displayed on the computer screen, along with instructions or error messages.

The computer systems train similar speech motor skills:

 Relaxed, diaphragmatic breathing. Continuous breathing. The computer alerts you if you hold your breath more than 1/3 of a second. Gradual exhalation, as opposed to the rapid, uncontrolled exhalation associated with stuttering.</li> <li>Pre-voice exhalation, or letting a little air out before you begin tensing your vocal folds.</li> <li>Gentle onset, or gradually increase vocal volume. The computer alerts you if your vocal volume changes too rapidly. The computer also alerts you if your voice is too quiet for your air flow (which sounds breathy).</li> <li>Continuous phonation. Breaks in vocal volume are shown on the computer monitor.</li> <li>Adequate breath support. The computer alerts you if you continue to talk after the point at which you should take another breath. Stutterers too often try to finish a phrase with insufficient air in their lungs.</li> <li>Phrasing. Each of the above seven speech targets is taught first with vowels, then progressing to monosyllabic words, then to marked-length phrases. Stutterers too often pause to breathe at feared words or when they run out of air, rather than pausing to breathe at linguistically-appropriate points.</li> </ol>

The CAFET and Dr. Fluency provide the following advantage over non-instrument-based stuttering therapy:

<ul> <li>The computer provides instant, accurate information on what you are doing right or wrong.</li> <li>The computers are always paying attention, and never get tired of helping you practice.</li> <li>The computers provide step-by-step instructions. Dr. Fluency has animated graphics showing what your speech muscles should do for each exercise.</li> <li>With the computer training the physical speech motor skills, the speech pathologist can spend more time on the psychological aspects of stuttering.</li> <li>If you learn visually rather than aurally, you may learn faster with the computer displays than by listening to your speech on a tape recorder.</li> <li>Dr. Fluency is designed for home practice use as well as clinical use. According to motor learning theory, practicing one hour per day is optimal. Practicing more hours per day or fewer days per week produces poorer results in the long run.</li> </ul>

An unpublished study of the CAFET program with 197 adults and teenagers reported that 82% met fluency criteria six months after completing the program; 89% were fluent after twelve months; and 92% were fluent two years post-therapy. These results are impressive, but unpublished studies are questionable.

Electromyography (EMG)

EMG measures muscle activity via electrodes taped to your skin. Several <a href="References.shtml#edn44">studies</a> found EMG to be effective for treating stuttering. These include the large study</a> that found computers to be more effective than speech-language pathologists.

My biggest fluency breakthrough was with EMG biofeedback. I brought my company's first EMG/DAF/FAF device to a speech-language pathology convention. For four days, eight hours a day, I showed hundreds of speech-language pathologists how the devices worked. I showed how tensing my vocal folds caused red lights and DAF/FAF to switch on, and relaxing my vocal folds made green lights go on and DAF/FAF to switch off. For a week after the convention I couldn't stutter. Eventually my stuttering returned, but daily use of the device on telephone calls kept my stuttering under control.

But EMG biofeedback isn't a &quot;miracle cure.&quot; Surface electrodes poorly monitor vocal fold activity (the primary symptom of stuttering), because vocal folds are deep in the neck, surrounded by other muscles. EMG devices are costly and difficult to set up. And even at the convention I heard speech-language pathologists laughing behind my back at the strange apparatus, with electrodes taped to my face and wires everywhere.

<a name="vocalfrequency">Vocal Frequency Biofeedback</a>

The great problem in stuttering therapy biofeedback is how to monitor vocal fold activity. EMG surface electrodes can't do this. The CAFET and Dr. Fluency monitor vocal fold activity indirectly via vocal volume. These devices assume is that a quiet voice means relaxed vocal folds, and loud voice means tense vocal folds. That isn't always true.

A better method is to monitor the frequencies of the stutterer's voice. Relaxed vocal folds generally produce a deep-pitched voice; tense vocal folds generally produce a high-pitched voice. The user simply speaks into a microphone; no electrodes are needed.

Vocal frequency biofeedback is also available in Kay Elemetrics' Visi-Pitch device, and in my company's Pocket Speech Lab. I've found that no one&#151;stutterers or speech-language pathologists&#151;can control the red and green lights when they first try the device. But after about ten minutes of training a light bulb goes on in their heads and they can easily control their vocal fold tension and vocal pitch, and make the light turn red or green at will. This suggests to me that no stuttering therapy programs train how to relax one's vocal folds. Many stuttering therapy programs claim to do this but I don't see the results. I suspect that &quot;gentle onsets&quot; are not the best way to train stutterers to speak with relaxed vocal folds.


 * Next chapter: Automatic, Effortless Fluency


 * Back to Table of Contents