Peter J. Alfonso

Measuring Stutterers’ Dynamical Vocal Tract Characteristics by X-ray Microbeam Pallet Tracking

Stuttering is generally considered to be a disorder of motor timing, yet neither the nature of the spatiotemporal interruptions of speech movements nor the physiological level(s) at which they occur is sufficiently understood. In particular, two critical questions that bear on the nature and treatment of stuttering, and by extension, the role of timing in various aspects of normal speech production remain unanswered. The first question concerns the anatomical locus of disordered motor timing. To what extent is the aberrant neuromuscular and kinematic activity that is associated with moments of stuttering specific to a single anatomical structure rather than spread throughout the speech production system? An aberrant state associated with a single structure, the larynx for example, might trigger abnormal activity in the respiratory and/or supralaryngeal systems. In this example, where laryngeal dysfunction precedes respiratory and supralaryngeal dysfunction, the activity of the latter systems might be viewed as compensatory rather than as an integral part of the stuttering breakdown. That is, the respiratory and supralaryngeal systems might be functioning to maintain appropriate temporal relationships with the abnormal laryngeal gestures.

Coordination of Prephonatory Events in Mild and Severe Stutterers

Many physiologically-based models of stuttering that associate laryngeal dysfunction with the disorder (Van Riper, 1971; Adams, 1978; Zimmermann, Smith & Hanley, 1981) share the hypothesis that stutterers have difficulty controlling the rapid initiation and termination of voicing. This hypothesis is supported by behavioral and physiological data drawn from samples of stutterers’ connected speech. Behavioral data show that stutterers demonstrate greater frequency of disfluency and less adaptation when reading aloud passages containing both voiced and voiceless segments than passages containing only voiced segments (Adams and Reis, 1971, 1974; Adams, Riemenschnieder, Metz & Conture, 1975). Physiologic data, obtained from fiberoptic viewing of the vocal folds (Conture, McCall & Brewer, 1977) and the recording of electromyographic (EMG) signals from intrinsic laryngeal muscles (Freeman and Ushijima, 1978; Shapiro, 1980), reveal evidence of abnormal laryngeal activity during stutterers’ disfluent utterances.

Context effects on the perception of place of articulation

The purpose of the experiment reported here was to determine the effect of phonetic context on the perception of place of articulation. Twelve place continua consisting of C1 VC2 stimuli were synthesized where C1 represented a stimulus taken from a 13‐step voiced or voiceless place continuum and C2 represented either /b, d, g, p, t, k/. The 156 stimuli (26 C1 × 6 C2) were randomized and presented to 21 subjects whose task was to label C1. Categorical boundaries were determined for the C1 stimuli and comparisons were made within different C2 place or voice contexts. The results indicated that the perception of place of articulation in C1 systematically varied as a function of place of articulation in C2. A somewhat less systematic C1 boundary shift was observed for C2 voiced‐voice‐less comparisons. Possible mechanisms accounting for the C1‐C2 interaction, articulatory compensation or psychoacoustic effect for example, will be discussed. [Work supported by NICHD NIH‐71‐2420 and University of Connecticut Res...

Discriminate acoustic cues in vowel sequence perception

In previous reports we have described the importance of smooth pitch continuities between adjacent first formants of four synthetic vowels /i,ae,a,u/for vowel temporal order identification [Kerivan and Alfonso, J. Acoust. Soc. Am. Suppl. 1 66, S86 (1979)]. In a followup study we asked trained listeners to discriminate vowel sequences which contained differences along the following physical parameters: (1) vowel permuted order, (2) vowel and intervowel durations ranging from 15–120 ms, and (3) pitch or loudness fundamental frequency contours, natural versus flat. Using a variable standard the task was to decide whether a “comparison” sequence was in any way different from a “standard” sequence. Preliminary results indicate that listeners can reliably discriminate (d′ = 1.0) natural from flat pitch contours of vowels in sequence at vowel durations as brief as 30 ms. They can also discriminate placement of a 15 or 30 ms intervowel duration in a given sequence at similar performance levels. Vowel permuted orde...

Traditional temporal measures are unstable and thus are inappropriate parameters to compare speech kinematics of control and stuttering populations

The aims of the study are to: (1) explore further the short‐ and long‐term flexibility in normal speech kinematics, and (2) identify relatively stable temporal characteristics that could function as appropriate experimental and control group comparative parameters. Movements of the tongue, lips, and jaw were transduced by electromagnetic midsagittal articulography. A single session included 20 perceptually fluent repetitions of /pap/, /tat/, and /sas/ imbedded in a carrier phrase at normal, slow, and fast speech rates. Seven stutterers and matched controls completed three sessions at 2‐week intervals. Reported here are across session comparisons of temporal ordering and relative timing for bilabial closure at normal rates. The prevalence and stability of the sequence pattern is dependent upon interarticulator relative time. Four control subjects and two stutterers showed idiosyncratic but stable temporal organizational characteristics within and across sessions. However, three of the controls and five of ...

Across session variability in lip–jaw synergies for bilabial closure.

Movements of the tongue, lips, and jaw were transduced by electromagnetic midsagittal articulography. A single session included 20 repetitions of

Across session temporal stability of the lip–jaw complex in bilabial closure

Movements of the tongue, lips, and jaw were transduced by electromagnetic midsagittal articulography. A single session included 20 repetitions of /pap/, /tat/, and /sas/ imbedded in a carrier phrase at normal, slow, and fast speech rates. Seven talkers completed three sessions at 1 week intervals. Reported here are across session comparisons of temporal ordering and relative timing of the movement of the lips and jaw for labial closure at normal rates. The predominant sequence patterns are those in which either upper or lower lip movement occurs first and jaw movement occurs last. Across‐subject comparisons show that either lip lead sequence is equally likely to occur. Within‐subject across‐session comparisons show no clear preference for either lip lead sequence for some subjects, and reversals in dominate lip lead sequences for other subjects. Across‐session stability of temporal order is related to interarticulator relative time: Subjects who demonstrate tight coupling of the upper and lower lips have ...

Across session spatial stability of the tongue‐jaw complex in alveolar closure

The movements of the tongue, lips, and jaw were transduced by electromagnetic midsagittal articulography. A single session included 20 repetitions of /pap/, /tat/, and /sas/ imbedded in a carrier phrase at normal, slow, and fast speech rates. Seven talkers completed three sessions at 1‐week intervals. Reported here are measures of across session stability of tongue and jaw spatial synergies for alveolar closure at normal rates. Preliminary analyses indicate that idiosyncratic organization of the tongue and jaw for alveolar closure is relatively stable within and across sessions. However, across session stability, in terms of the relative contribution of the tongue and jaw towards closure and motor equivalence covariability of the summed tongue‐jaw, the jaw, and the derived independent tongue displacements, is sensitive to variations in normal speech rate. For example, tongue‐jaw synergies varied when the difference between session average duration of the tongue and/or jaw gestures approached 30%. [Work supported by NIH DC‐00121 to Haskins Laboratories and University of Illinois research grant.]

Patterns of correlation of tongue movement and electromyographic signal in vowel production.

X‐ray microbeam data from pellets on the jaw, tongue, and lips were compared with EMG signals from eight muscles for production of multiple tokens of 11 vowels in /schwapVp/ context, for an American English speaker. Pellet data were obtained from the Tokyo x‐ray microbeam while electromyographic data were obtained at Haskins Laboratories. Acoustic recordings and a comparison of orbicularis oris electromyographic records with lip pellet movement data were used to link the two data sets, so that an estimate of muscle contraction time could be made and appropriate correlations of time functions across the sets generated. Tongue pellet data were adjusted to compensate for the effects of jaw position. Relations between EMG and movement signals for the point vowels /i/, /open aye/, and /u/ were as expected, in that movements up and front were accompanied by large signals from anterior and posterior genioglossus, movements up and back were accompanied by large signals from styloglossus, while tongue lowering mov...

Modifications to stutterers’ respiratory, laryngeal, and supralaryngeal kinematics that occur with fluency improvement

Within‐subject pre‐ and post‐therapy kinematic comparisons of two groups of stutterers who successfully completed one of two intensive therapy programs revealed that certain aberrant kinematic profiles can be modified as a result of therapy, that post‐therapy improvement in fluency co‐occurred with spatial and temporal adjustments in each of the three systems, that some of the post‐therapy kinematic modifications were in the direction of normal speech kinematics observed in the control subjects, and that certain modifications occurred across both groups of stutterrers although the clinical instructions differed. While some of the kinematic modifications appear related to specific clinical strategies associated with each therapy program, those that occurred across both groups of stutterers do not and may be related to normal motor control strategies that underline the production of rapid, perceptually fluent speech. [Work supported by NIH DC 00121 awarded to Haskins Laboratories.]