Research on the pathogenesis of stammering

Communication by Alfred Tomatis presented at the 13th Congress of the Société Française de Phoniatrie, Paris, 25 October 1953, and published in the Journal Français d’Oto-Rhino-Laryngologie (vol. III, no. 4, 1954, pp. 92-99). Tomatis there reports the results of audiometric and phonatory examinations conducted on stammerers at the Hôpital Saint-Michel — following a demonstration given by Dr Decroix-Tomatis and Dr Trojman on the delayed feed-back test — and proposes a pathogenic interpretation: stammering would translate a disturbance of the transcerebral transfer of audio-phonatory control, linked to a defect of the right directing ear in the right-handed subject.

Research on the pathogenesis of stammering

by Dr A. Tomatis

Communication presented at the 13th Congress of the Société Française de Phoniatrie, Paris, 25 October 1953.
Reprint from the Journal Français d’Oto-Rhino-Laryngologie, vol. III, no. 4, 1954, pp. 92-99.

I. — Introduction

Some months ago now, the day after a demonstration given by Dr Decroix-Tomatis, of the S.F.E.C.M.A.S. Research Laboratory, and Dr Trojman, on the “delayed feed-back” test, the following question was put to us: is there an auditory anomaly that can account for stammering?

To study this very interesting problem, before any experimentation, we thought that an anomaly capable of generating an auditory delay of speech, of the order of 0.10 to 0.20 second, might exist. This anomaly might present itself, for example, in the form of an auditory distortion brought about either by an ear that lagged with a certain delay on the second, or by a kind of auditory astigmatism.

We began by carrying out audiometric examinations on every subject encountered with more or less marked stammering. The conclusions were simple. All the subjects examined at the start of this work belonged to the Re-education Service of the Hôpital Saint-Michel (Mlle Drouville).

The subjects of the Hôpital Saint-Michel were all right-handed. Among the others, four only were left-handed.

II. — Audiometric results

The results obtained were all identical:

All the right-handed subjects have a right-side hypoacusis, without exception.
The four left-handed subjects we were able to examine have a left-side hypoacusis.

This hypoacusis is a relative hypoacusis, of slight importance, not appreciable on simple examination and unknown to the individuals themselves, who do not seem hampered by it; it more readily affects the conversational zone.

We report here, by way of examples, a few of the audiograms obtained (figures I, II, III, IV).

[Fig. I to IV — characteristic audiograms showing the hypoacusis of the directing ear (right in the right-handed, left in the left-handed).]

III. — From hypoacusis to auditory trauma

Did this anomaly suffice to account for the auditory delay we were seeking? We were tempted to believe so.

Indeed, in numerous experiments carried out on the productions of professional singers, we had noted that an auditory trauma on the melodic line provoked an auditory trauma on the right ear for right-handed subjects, on the left ear for left-handed subjects.

We had noted, moreover, that no modification was observed if the trauma was inflicted on the opposite ear — that is, in the left-handed on the right-handed, in the right-handed on the left-handed. We had thus admitted then that the right ear in right-handers, or the left ear in left-handers, was a directing eye, that there existed a directing ear: the right ear in right-handers, the left ear in left-handers.

When we presented these experiments at the 12th Congress of Phoniatrics, we were not in a position to give a valid explanation or to specify the phenomenon of the dazzling which, in certain singers, could become considerable.

Subsequently, we resumed our experimentation on auditory dazzling in order to study the disorders it brought about on the spoken voice. This dazzling is obtained by the emission, to the directing ear, of a 2,000 cycles-second sound at an intensity of 100 dB for a duration of 5 seconds on average, depending on the prior audio of the subject examined, and which entails his resistance to auditory fatigue.

This test produces on the ear a trauma sufficient to modify the audiometric curve for a time that may vary from one minute to a quarter of an hour, according to the subject’s possibilities of recovery. As one can see on the curves (fig. 5 and 6) we reproduce here, the quantitative modification on acoustic examination, although appreciable, is not of such importance as to disturb the subject in his audition.

[Fig. V and VI — audiometric modification after dazzling.]

IV. — Effect on the spoken and sung voice

As we had foreseen, we obtained immediately a slowing of speech, a phenomenon all the more evident in that it was obtained in so striking a fashion on the sung voice.

Furthermore, as soon as the subject sought to fight against the slowing, of which he was likewise conscious, a characteristic stammering appeared, identical to that obtained with the “delayed feed-back” apparatus. There too, as B. S. Lee, John Black, Azzo Azzi and Bernard-Joseph Tankerrey had remarked, all the subjects examined did not present identical disorders as to their intensity.

In other words, everything proceeds as if the hypoacusis observed on the directing ear, however slight, sufficed to eliminate partially from the normal cochleo-phonatory circuit.

For greater understanding, we reproduce (fig. 7) schematically the normal cochleo-phonatory circuit.

[Fig. VII — diagram of the normal cochleo-phonatory circuit: hearing centre → directing ear → phonatory centre.]

One notes that the sound, emitted on speaking, reaches the directing ear, that is to say the right ear, the case chosen being that of a right-handed subject. From there, it is directed towards the hearing centre, close to the hearing centre, whose function transmits this signal to a phonatory centre which seems to be, under the circumstance, under the permanent control of the hearing centre. Once this control is completed, the nervous influx is directed towards the phonatory organs.

V. — The “transcerebral transfer”

In the case where the directing ear is not used to regulate phonatory control, this control then falls under the dependence of the opposite ear, that is to say of the left ear, the example chosen, let us recall, being that of a right-hander (fig. 8). The sound thus reaches the left ear, from there to the right brain, at the level of the auditory centre whose control, once completed, must reach the left phonatory centre, that is to say the motor side. From this last centre, the process remains the same in the direction of the phonatory organs.

[Fig. VIII — transcerebral detour: left ear → right auditory centre → left phonatory centre.]

This time of “transcerebral transfer” seemed bound to be an organic disorder sufficient to account for the delay of audition on speech. We thought to measure it, and we proceeded in the following manner:

First of all, by having a prefabricated text read, of which one counts the number of syllables it contains, without noting any auditory perturbation, its duration.

Then, by neutralising the directing ear, one obtains immediately a slowing whose value can be calculated.

Knowing this latter value, we know the times to be imposed, on the directing ear, a delay sufficient to obtain the same slowing of the speech rate. Now, the delay is that which corresponds to the time of the cerebral transfer.

This measurement is easy and quick to obtain. It requires practically no special apparatus. Indeed, since the “delayed feed-back” of Bernard-S. Lee, we have used a long 110-metre garden hose (it was impossible for us to procure the apparatus of Bernard-S. Lee).

Lateral perforations were made along the hose, so as to produce the desired delay times between 1/200 and 1/3 of a second. We obtained the following results:

When the latency time remains under 1/10 of a second, the subject on whom an auricular inversion is imposed becomes a “stuttering” bradylalic. He will speak slowly, searching for his words, on an imprecise rhythm.
When the latency time is between 1/10 and 1/20 of a second, the subject submitted to the test reproduces the “stammered”, this phenomenon appearing at a maximum when the delay imposed is 1/15 of a second.
Lastly, when the delay exceeds 1/20 of a second, the subject becomes a very pronounced bradylalic. Beyond the bradylalic, one stumbles. The subjects of this last group speak with a slowed but homogeneous rhythm, without hesitation. The prolonged listening of the test, by imposing a delay of the order of 1/20 of a second, provokes a stammering in the listener. The 15th word becomes more nuanced, the subject giving the impression of listening to himself speak as in the echo of a great hall.

These results are interesting because they bring out, in striking fashion, the personal and individual factor in the genesis of stammering.

VI. — Aetiology and factors of fragility

The demonstration of this transcerebral transfer makes it possible, to a large extent, to explain the aetiology of stammering. We think that there exists, if not the only one, at least in the cases we have encountered in the course of this work, an organic origin capable, on its own, of accounting for stammering. But perhaps it is not the only one.

The existence of the auricular disorder from the very course of the work to which we have referred at the start of this study, makes it possible to provide plausible solutions to certain problems:

Influence of age. — It is with a maximum frequency that stammering appears between three and five years of age. It is the period when language takes a large place in the life of the child, whose hearing-phonation circuit is still very fragile. It is also the age when the child most frequently presents affections of his middle ear, thus making this auditory disorder transient but important in the cochleo-phonatory circuit.
Personally, we have had occasion to examine a little girl of four and a half who presented an acute stammering following a left-side influenzal otitis of the right ear. The disorder disappeared at the same time as the otitis. This disorder disappeared at the same time as the otitis.
Influence of sex. — It has been noted that stammering is much more frequent in men than in women, and, according to the authors, there would be 5 to 9 stammering men for one stammering woman. Resistance to stammering is much greater in women than in men, which would account for the disproportion of which we have just spoken.

We have spectrographically studied a few women’s voices that we had had heard well. Contrary to the male voice, the spectrum of the female voice is very rich in high harmonics, in a wide band exceeding 2,000 c/s. Moreover, by studying the spectrum of the singer, we noted that the presence of a sheaf of harmonics located at 2,000 c/s exceeding this point makes auditory control by bone conduction possible.

Experimentally, we realised a hearing-phonation circuit in the man by frequency cuts using filters. We blocked the harmonics up to 1,500 c/s. One notes immediately, in the woman, a much lower voice, and moreover the delayed feed-back tests give results absolutely identical to those observed in the man.

It follows that the fact that women retain their possibility of cochleo-phonatory self-control by bone conduction makes it possible to account for the fact that conduction hypoacuses, generated by affections of the middle ear, are not compensated for. By contrast, deafnesses, even slight, of the perception type will generate, through the elimination of bone control, disorders of phonation identical to those of the male sex.

Conduction hypoacuses are moreover much more frequent than perception hypoacuses, which is no doubt one of the most due to the greater resistance offered by the female sex to stammering. It remains to prove, by statistics, that the proportion between the two types of relative deafness is of the order of 3 to 9 against one.

The problem of left-handers. — The problem of the inverted right ear-left brain-phonatory organs circuit finds its explanation long since in this same re-education in the child. This perturbation is easily explained by the fragility, at this age, of the cochleo-phonatory circuit. One may admit that this re-education requires a mechanisation due to the appearance of the latency time of transcerebral transfer, origin of the disorders of phonation.

Lastly, a final argument, no doubt the most important, in favour of the auricular origin of stammering is the immediate reduction of the disorders that characterise it as soon as the cochleo-phonatory circuit is restored. This last operation is obtained by setting the directing ear slightly hyperacusic, that is to say by increasing the transcerebral transfer, origin of the suppression of the phonation identical to those of the male sex, and thus all trace of bone control.

The application of this test is spectacular, for not only is elocution rapidly restored to a normal manner, but, moreover, within a few moments, all the associated signs are seen to disappear. What strikes one most is the physical relaxation felt by the patient.

This last test is, in our view, of capital importance, for, besides the theoretical support it brings us, it is at the same time the best therapeutic adjunct that can be proposed.

There is here, for pedagogues, a procedure which, associated with those they use, must be of valuable help.

Discussion

Prof. Ag. Greisen (Strasbourg). — I am very interested in Dr Tomatis’s audiograms, but I should like to know how he explains the hyperacusis of the highs, which is not due to habit, and, on the other hand, how the bone conduction curve behaved in these patients.

Dr Decroix (Lille). — It would be interesting to know whether the hypoacusis translated by a lowering of the tonal threshold is or is not accompanied by recruitment, whether the auditory value at the intensity of a normal conversation does not seem important to note in the subject.

On the other hand, in the course of cerebral interventions on a lobe or a hemisphere, one does not create stammering. Lastly, if the hypothesis is attractive, it does not explain the subsequent mechanisms of stammering.

Mme Borel-Maisonny (Paris). — Among the hypo-acoustic (loss of 30-40 dB) who are re-educated at the Enfants Assistés, there has been little inequality between the curves of the right and left ear. I have never observed stammering in these subjects.

The statistics of the percentages of stammering according to sex, given by Dr Tomatis, seem to agree with the disparity of the figures, that men are affected in a stronger proportion than women. It is said, statistics show, according to the schools, of hypoacusics on average an equal distribution according to sex.

In psycho-acoustics, an inequality in the auditory acuity of the two ears often manifests itself, but no stammering is seen. One of the subjects treated by Dr Tomatis seems to me to present disorders of perception more than of auditory acuity. I cannot forget that there frequently are in them important difficulties in the perception and execution of rhythm.

Source: Tomatis A., “Recherches sur la pathogénie du bégaiement”, communication presented at the 13th Congress of the Société Française de Phoniatrie (Paris, 25 October 1953), published in the Journal Français d’Oto-Rhino-Laryngologie, vol. III, no. 4, 1954, pp. 92-99. Work carried out at the O.R.L. Service of the Hôpital Bichat (Dr Decroix-Tomatis) and at the S.F.E.C.M.A.S. Research Laboratory — Re-education Service of the Hôpital Saint-Michel (Mlle Drouville). Document digitised from the personal archives of Alfred Tomatis.