Before any bodily movement can occur, the brain must create a motor program to determine when and how the appropriate muscles are to be activated.  The same is true for speech.  A process of neuromotor tuning takes place during the split second before normal speech, preparing the speech mecha­nism to perform the activities that will be required.  The preparation for phonation also includes a process called prephonatory tuning.   This adjusts the tension of the vocal folds, so they will be ready to vibrate at the right pitch as the airflow passes between them.  Scientific studies have found that prephonatory tuning occurs from about one‑half a second to 1/20th of a second before phonation is heard.

It now appears that Valsalva-stuttering blocks occur because the brain has not supplied the neurological motor program for the larynx to phonate the vowel sound for a specific word or syllable.  Instead, the brain has substituted the neurological motor program for effort closure (which is the larynx’s function in the performance of Valsalva maneuvers).

Take, for example, the name “Peter” (represented in the phonetic alphabet as /'pi · td/).  Before Peter can say his name, his brain must neurologically program the muscles of his mouth and larynx to make the necessary movements and to bring his vocal folds together at the right time and with the right amount of tension to say the vowel.  But, because Peter anticipates that saying his name will be difficult, his brain decides to insert a motor program for exerting extra effort.  So, instead of preparing the larynx to phonate the vowel sound “ee” (/i/) in “Peter,” the brain instructs the larynx to do effort closure.  The vowel portion of a word or syllable is the natural place to insert the motor program for effort, because that is the place in a syllable that usually is loudest and has the most energy.

The motor program for “Peter” should have phonation on the “ee” (/i/) and the “er” (/d/), which could be represented like this:

p ee t r   (/'p i · t d/)

Instead, the brain sends a motor program containing effort closure where the “ee” should be, which we will represent like this:

p r t r   (/p r t d/)

To the speaker, the word or name feels as if it contains a “brick wall” that requires effort to break through.  As a result, the speaker may become fixated on the articulation that precedes the missing vowel sound – either repeating or prolonging it or exerting force on it.  The speaker may try to force through the block by building up air pressure, as in a Valsalva maneuver.  The lips, tongue, or larynx may press tightly to block the upper airway, while the chest and abdominal muscles squeeze to exert pressure on the lungs.  The muscles of the Valsalva mechanism are neurologically coordinated to build up air pressure; therefore, the greater the air pressure, the greater the blockage becomes.  While this effort may instinctively feel like the right thing to do, it actually strengthens the block and makes phonation of the vowel sound even more difficult.

In Peter’s case, the resulting forceful blockage of air by the lips might be represented like this:

P------- r    (/p------- r /)

Peter’s repetition of the initial consonant might be represented like this:

Puh-puh-puh-puh r    (/pc-pc-pc-pc r/)

When the initial consonant is repeated during stuttering, it is usually followed by a neutral vowel sound, “uh” (/c/), which is called the schwa.  This is simply the sound of a grunt, rather than the vowel that properly belongs in the word or syllable.

To the speaker, it seems as if the initial sound is causing the block.  Therefore, Peter may believe that he blocks on the “p” sound – when actually he was making the “p” perfectly well.  His real problem was his inability to move on to the vowel sound that followed it.

When the beginning consonants do not completely block airflow, such as fricatives, liquids, and nasals, the result may be a prolongation of the sound, such as:

Ssssssssss r   OR    rrrrrrrr r    OR     mmmmm r

Blockages may occur in either the mouth or the larynx, usually depending on where articulation occurred prior to the missing vowel.  Because the “h” sound is produced by partial closure of the larynx, blockages that focus on that sound may also involve laryngeal closure. 

It should be noted that the difficulty in phonation is usually limited to a specific vowel sound in a specific word or syllable.  Therefore, the larynx may be able to make prolonged phonation on initial voiced consonants like “r” or “m,” but not be able to phonate the subsequent vowel sound.

In words that start with vowels (e.g., “apple”), the block may focus on the laryngeal closure or “glottal stop” (/§/) that commonly occurs just before the vowel when the speaker does a “hard onset.”  This kind of repetition or block could be represented as follows:

§uh-§uh-§uh-§uh r     OR     §--------------- r

This fixation on the initial sounds creates the false impression that these sounds are causing the speaker to block, when the real problem is the speaker’s inability to move on to the vowel sound that follows.  The speaker may come to anticipate difficulty in saying words that begin with certain sounds.  This anticipation will reinforce the brain’s tendency to substitute the motor program for effort in an attempt to “force out” the feared words.  The speaker may also try to avoid, delay, or hide the blocks by interjecting extraneous words or sounds as “starters” (e.g., “um,” “you know,” “§uh-§uh-§uh-§uh”) or by substituting words that he or she feels will be easier to say.  Persons who stutter may also resort to a variety of other behaviors in their struggle to force out words.

The intensity of the speaker’s urge to exert effort may vary, depending on the word or the speaking situation.  Therefore, some blocks may be relatively brief, such as:

Puh-puh r ee t r   OR    P--- r ee t r

In other instances, the block may go on indefinitely.  Or it may continue until the muscles blocking the upper airway tire out.  Nevertheless, any amount of excessive effort is likely to disrupt fluency.

Valsalva Control Therapy employs a variety of speaking exercises and psychological approaches that are designed to reduce these types of stuttering blocks.

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Copyright © 2011 by William D. Parry