Respiratory-swallowing coordination in normal subjects: Lung volume at swallowing initiation.

This study was designed to investigate the significance of bolus types and volumes, delivery methods and swallowing instructions on lung volume at swallowing initiation in normal subjects in a single experiment using a multifactorial approach. Our broad range goal was to determine optimal lung volume range associated with swallowing initiation to provide training targets for dysphagic patients with disordered respiratory-swallow coordination. Our hypothesis was that swallows would be initiated within a limited range of quiet breathing lung volumes regardless of bolus volume, consistency or task. Results confirmed this hypothesis and revealed that swallows were initiated at mean lung volume=244ml. Cued swallows were initiated at lower quiet breathing volumes than un-cued swallows (cued=201ml; un-cued=367ml). Water boluses were initiated at slightly higher quiet breathing volumes than solids. Data suggest that swallows occur within a restricted range of lung volumes with variation due to instructions, bolus type and other experimental variables.

Speech with maxillary implant prostheses: ratings of articulation.

Speech is often perturbed after placement of maxillary implant-retained prostheses. We tested the hypothesis that the rate of speech errors varies with prosthetic design. Thirty edentulous subjects with mandibular implant prostheses entered two within-subject crossover trials. Subjects wore maxillary fixed prostheses and removable long-bar overdentures (Trial 1), or overdentures with and without palates (Trial 2). Test words from a French language speech battery were recorded after each prosthesis had been worn for two months. The percentages of stops, fricatives, and vowels correctly perceived by lay judges were calculated. Subjects produced a significantly higher percentage of sounds correctly with overdentures than with fixed prostheses. Between-treatment differences were significant for stops and fricatives (p < 0.01), but not for vowels. There were no significant differences in error rates between the two overdentures. In conclusion, maxillary implant overdentures with and without palates enable patients to produce more intelligible speech than fixed prostheses.

Respiratory markers of conversational interaction.

Respiratory movements were recorded from 10 dyads (20 subjects) during quiet breathing, reading aloud, spontaneous monologue, scripted dialog, and spontaneous conversation. Timing measures of inspiratory, expiratory, and total cycle duration were used to compare respiratory function during quiet breathing, listening, and speech. Cross-correlation analyses of the respiratory movements of conversational partners provided an index of conversational synchrony. Inspiratory duration was found to be the most consistent and sensitive measure for discriminating quiet breathing from speech breathing. In the scripted dialog and spontaneous conversation conditions, respiratory kinematics changed during listening to more closely resemble speech, and systematic changes were observed in anticipation of turn-taking speech onset. For the breathing cycles immediately surrounding turn changes and simultaneously produced vocal events, the kinematic signals of conversational partners were strongly correlated. Results are discussed in the context of similar findings concerning conversational interactions and motor preparation for speech.

The development of speech adaptation to an artificial palate.

An investigation of adaptation to palatal modification in [s] production was conducted using acoustic and perceptual analyses. The experiment assessed whether adaptation would occur subsequent to a brief period of intensive, target-specific practice. Productions of [sa] were elicited at five time intervals, 15 min apart, with an artificial palate in place. Between measurement intervals, subjects read [s]-laden passages to promote adaptation. Results revealed improvement in both acoustic and perceptual measures at the final time interval relative to the initial measurement period. Interestingly, the data also suggested changes to normal (unperturbed) articulation patterns during the same interval. Results are discussed in relation to the development of speech adaptation to a structural modification of the oral cavity.

Speech compensation to structural modifications of the oral cavity.

Acoustic and perceptual analyses of vowels, stops, and fricatives produced with and without an artificial palate were conducted. Recordings were made both immediately upon insertion of the palate and following a 15-min adaptation period. Results of the acoustic analyses revealed significant alterations in the fricative spectra under conditions of perturbation with fewer, if any, changes in the vowels and stop consonants. Perceptual data confirmed these patterns and provided evidence of possible improvements in compensation over time. The data are compared to our previous studies of speech sound articulation under bite-block conditions. Differences between adaptation to modifications of oral structure (artificial palate) and oral function (jaw fixation by a bite block) are considered.

Compensation to articulatory perturbation: perceptual data.

The perceptual adequacy of vowels, stop consonants, and fricatives produced under conditions of articulatory perturbation was explored. In a previous study [McFarland and Baum, J. Acoust. Soc. Am. 97, 1865-1873 (1995)], acoustic analyses of segments produced in two subtests (immediate compensation and postconversation) revealed small but significant changes in spectral characteristics of vowels and consonants under bite-block as compared to normal conditions. For the vowels only, adaptation increased subsequent to a period of conversation with the bite block in place, suggesting that compensation may develop over time and that consonants may require a longer period of adaptation. The present follow-up investigation examined whether the acoustic differences across conditions were perceptually salient. Ten listeners performed an identification and a quality rating task for stimuli from the earlier acoustic study. Results revealed reductions in identification scores and quality ratings for a subset of the vowels and consonants in the bite-block conditions relative to the normal condition in the immediate compensation subtest. In the postconversation subtest, quality ratings for the fricatives in the bite-block condition remained low as compared to those in the normal condition. Perceptual results are compared to the previous acoustic data gathered on these stimuli.

Modification of mastication and respiration during swallowing in the adult human.

1. The normal interactions between respiration, mastication, and swallowing were studied in seated adult humans. Respiratory movements and movements of the larynx were recorded with mercury-elastic strain gauges placed around the rib cage and neck. A rigid body containing infrared-emitting diodes (IREDs) was attached to the forehead, and a single IRED was applied to the chin. Jaw and head movements were transduced using the OPTOTRAK spatial motion analysis system. Recordings were made before, during, and after the mastication of pieces of carrot. 2. Movements of the larynx were used as a marker for swallowing. Measurements were made of the duration of masticatory and respiratory cycles, and the phase relationship between the two rhythms was determined. Deviations in masticatory and respiratory movements during swallowing were detected; the phases of the masticatory and respiratory cycles in which the deviations occurred were determined, and the interval between each deviation and the swallowing marker was calculated. 3. Three characteristic swallowing patterns were observed: interposed, terminal, and spontaneous. Interposed swallows occurred within a masticatory sequence, terminal swallows ended the sequence, and spontaneous swallows occurred sporadically between masticatory sequences. 4. Results revealed that mastication could have a profound effect on the respiratory rhythm in some subjects. One subject, whose data were excluded from further analyses, became apneic for a long period, followed by short and shallow breaths near the end of the masticatory sequence. In most subjects, respiratory rate increased during mastication and then dropped below baseline as soon as mastication ended. The end-inspiration diameter of the rib cage tended to decrease in the preswallow period and increase postmastication relative to baseline. 5. There was a weak but significant tendency for inspiration to begin during the jaw opening phase of mastication, but phase coupling did not become stronger as swallowing was approached. 6. Deviations in respiration during swallowing occurred during the late expiratory phase of the breathing cycle. Swallows within a masticatory sequence occurred most frequently during the early opening phase of the masticatory cycle, and terminal swallows occurred after the end of the sequence with the mandible in the resting, postural position. Swallowing temporarily reset both the masticatory and respiratory rhythms. Most swallows prolonged the duration of one or two respiratory cycles, however; swallows were often repetitive, and in some subjects two or three swallows fell within a single respiratory cycle, prolonging it for several seconds. 7. A tight temporal relationship was observed between deviations in respiration and the swallowing marker: all deviations occurred before or coincident with the marker. The time of deviations in mastication relative to the swallowing marker depended on swallow type. There was no link between the start of pauses in the two rhythms, suggesting that the commands from the swallowing central pattern generator to the other two pattern generators are independent. 8. We suggest that disordered coordination of mastication and swallowing with respiration may cause prolonged apnea in susceptible individuals.

Incomplete compensation to articulatory perturbation.

Measurements were made of vowels, fricatives, and stop consonants produced by 15 adult speakers of French in one free-mandible and two fixed mandible conditions. Speech acoustic data were recorded immediately upon bite-block insertion and after a 15-min accommodation period. Results indicate that compensation to increased jaw opening during speech is neither immediate nor complete as there were small but significant differences in the acoustic parameters of vowels and consonants produced under bite-block and normal conditions. Further, the data suggest that, at least for vowels, speech compensatory strategies may develop over time, perhaps involving error-based correction. Consonants appear to require a more lengthy period of speech adaptation, and this may be due to the articulatory requirements for their accurate production. Individual differences in compensatory abilities are also discussed.

Effects of posture on the coordination of respiration and swallowing.

1. Although a pause in respiration during swallowing is a feature common to all mammals, inhibition usually occurs during expiration in adult humans and during inspiration in most other species. We tested the hypothesis that this difference is due, at least in part, to the position of the body while feeding. 2. The coordination of respiration and swallowing was studied in adult human subjects in two body positions; upright, which is typically human, and on hands and knees, which is similar to the feeding posture of most other animal species. 3. Our major finding was that the respiratory phase in which swallowing occurred was significantly related to posture. Swallows tended to occur late in the expiratory phase while feeding upright, but during early expiration while on all fours. 4. We speculate that the phase of respiration in which swallowing occurs changes with posture to compensate for the alterations in the mechanical properties of the upper body.

An investigation of the coupling between respiration, mastication, and swallowing in the awake rabbit.

1. The interrelationships between respiration, mastication, and swallowing were studied in awake rabbits previously prepared for the chronic recording of jaw movements and the electromyographic activity of jaw and throat muscles. These signals were recorded before, during, and after the mastication of rabbit chow, together with respiratory movements. 2. The onset of activity in the thyrohyoid muscle was used as a marker for swallowing. Measurements were made of cycle duration, and the phase relationship between the masticatory and respiratory rhythms was calculated. Deviations in masticatory and respiratory movements during swallowing were detected; the phases of the masticatory and respiratory cycles in which the deviations occurred were determined, and the intervals between the deviations and the swallowing marker were calculated. 3. Two characteristic swallowing patterns were observed that were called Interposed and Terminal swallows. Interposed swallows occurred within a masticatory sequence, while Terminal swallows ended the sequence. 4. In most rabbits, respiratory rate slowed during mastication. This brought the average frequency of the two movements closer together, and there was a weak but significant correlation between the masticatory and respiratory rates. However, respiration and mastication were not linked on a cycle-by-cycle basis, and the change in respiratory rate was found to be unrelated to masticatory rate. Further, there was no tendency for the masticatory and respiratory rhythms to adopt any particular phase relationship as swallowing was approached. Some weak and transient phase coupling of the two systems occurred after swallowing. 5. During swallowing, respiration was most often inhibited soon after the start of the inspiratory phase. Swallows within a masticatory sequence occurred most frequently during the early opening phase of the masticatory cycle, and swallows after the end of a sequence occurred with the jaw in the resting position. There was a strong tendency for the durations of the masticatory and respiratory cycles containing deviations to be longer than preceding control cycles, and the effect on respiration lasted several cycles. 6. For both Interposed and Terminal swallows, a tight temporal relationship was observed between deviations in respiration and the swallowing marker: most deviations tended to occur before swallowing. In contrast, the time of deviations in mastication relative to the swallowing marker depended on swallow type and was more variable. Finally, there was no link between the start of the pauses in the two rhythms. 7. We conclude that respiratory and masticatory processes are not strongly coupled.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of vocal task and respiratory phase on prephonatory chest wall movements.

A vocal reaction time paradigm was used to explore prephonatory respiratory kinematics. Movements of the rib cage and abdomen were recorded prior to production of utterances differing in length and intensity, and vocal responses were elicited in different phases and volumes of the quiet breathing cycle. A velocity threshold was used to distinguish prephonatory adjustments from the cyclical movements of the chest wall that are characteristic of quiet breathing. The results suggest that a variety of prephonatory kinematic events can occur prior to initiation of vocalization in response to a stimulus. Further, prephonatory movements appear to be adaptive in that they are influenced by the length of the utterance to be spoken and the respiratory volume at the time of voice initiation.

Surface recordings of respiratory muscle activity during speech: some preliminary findings.

Bipolar electromyographic (EMG) recordings were made from six chest wall and nasal sites with disk electrodes attached to the skin. Electrode locations were based on previous studies of nonspeech breathing and were designed to sample the activity of both primary and accessory respiratory muscles. EMG activity was sampled while subjects performed a series of speech and nonspeech tasks. The results revealed that surface electrodes could sample the activity of respiratory muscles during speech and other ventilatory tasks, particularly during the expiratory phases of the breathing cycle.

Spatial organization of human perioral reflexes.

Reflex responses recorded from the upper and lower divisions of the human orbicularis oris muscle were studied as a function of the site of stimulation. Stimuli were applied to 11 sites, ranging from the glabrous skin of the upper and lower lip vermilion borders to the hairy skin of the cheek. Highly localized, innocuous mechanical stimuli were created by displacing a servo-controlled probe over the surface of the perioral skin. Reflex response amplitude was strongly dependent on the site of stimulation. Stimulation of some sites, for example the ipsilateral corner of the mouth, the chin, and cheek, produced no responses, whereas stimulation of other sites, particularly the ipsilateral vermilion borders, produced large reflex responses. Changes in response amplitude as a function of stimulation site were the same for the upper lip and lower lip muscle recordings, with the largest responses at both recording sites produced by stimulation of the ipsilateral upper lip vermilion border. These results suggest that the upper and lower divisions of orbicularis oris share common synaptic drive, at least from inputs generated via reflex pathways, and that the upper vermilion border may be more densely innervated with mechanoreceptors than the lower. The latter hypothesis was supported by an additional experiment examining two-point discrimination thresholds for the glabrous skin of the upper and lower lips. Two-point thresholds were significantly smaller for the upper compared with the lower lip vermilion border.

Interactions between speech and finger movements: an exploration on the dynamic pattern perspective.

Under the dynamic perspective for motor control, movement is viewed as an "emergent" property, arising from cooperative relationships among limit-cycle oscillators. This is in contrast to more traditional approaches to motor control in which a central representation of movement is usually assumed to exist. The assertion that coordination of movement arises from interactions between oscillatory processes leads to some unexpected predictions. In particular, interactions between frequency and amplitude of simultaneously performed speech and manual tasks are predicted, because the organism "parameterizes" all ongoing oscillatory processes as a "total unit." Using quantitative analyses, we have demonstrated that interactions between speaking and finger tapping do occur in both the amplitude and frequency domains. Such interactions, however, do not appear to be as simple as those predicted by proponents of the dynamic pattern perspective.

Relationship between amplitude of tremor and reflex responses of the human jaw-closing system.

Jaw-closing force was transduced while subjects maintained a biting force of 9.8 N. To estimate the amplitude of tremor in each subject's force record, the average spectrum of the force was computed, and the definite integral of the averaged spectrum in the frequency range from 3.5 to 10 Hz was calculated. For the same subjects, the amplitude of reflex responses to innocuous mechanical stimuli delivered to intraoral and perioral sites was measured as the peak-to-peak change in jaw-closing force following application of the stimulus. Force responses produced by stimulation at each site were used to compute an average reflex response measure for each subject. Large intersubject variability was observed in the amplitudes of jaw tremor and reflex responses. A correlation coefficient computed between the tremor and reflex measures revealed that subjects with large amplitude tremor tended also to have large reflex force responses. This correlation is consistent with the suggestion that activity in cutaneous reflex pathways contributes to tremor of the human mandible.

Reflex responses of the human jaw-closing system depend on the locus of intraoral mechanical stimulation.

Innocuous mechanical stimuli were applied to eight sites on the tongue dorsum and palate while subjects used feedback to maintain a constant isometric biting force. Reflex responses of the jaw-closing system were measured as changes in force and in EMGs recorded from right and left masseter muscles. Stimulation at each of the eight sites produced reflex force and EMG responses in most subjects tested. The nature of the reflex responses strongly depended on the site of stimulation. Stimulation of the palate tended to produce suppression of ongoing EMG activity and decreases in background biting force. In contrast, stimulation of sites on the tongue posterior to the tip, most often resulted in excitatory EMG responses and increases in jaw-closing force. Unilateral, early excitatory responses were observed in the right masseter with stimulation of the right side of the tongue. The existence of spatially organized responses of the human jaw-closing system to innocuous intraoral stimulation is not consistent with the view that these cutaneous reflexes are primarily of protective significance.

Reflex responses of human lip muscles to mechanical stimulation during speech.

The role played by reflex pathways in the production of movement has been a significant issue for motor control theorists interested in a wide variety of motor behaviors. From studies of locomotion and chewing, it appears that gains in reflex pathways can be altered so that activity in these pathways does not produce destabilizing responses during movement. In speech production, recent experimental evidence has been interpreted to suggest that autogenetic lip reflexes (perioral reflexes) are suppressed during sustained phonation or speech production. The present study was conducted to assess the effects of phonation, direction of movement, and ongoing speech production on reflex responses of lip muscles. The present results suggest, in contrast to earlier work, that this reflex pathway is not suppressed or absent because the amplitude of the observed response depends upon the activation levels of the various muscles of the lower lip and, therefore, indirectly on the nature of the gesture the subject is instructed to produce.

Ophthalmic surgery and plasma thromboplastin antecedent (factor XI) deficiency.

A patient had bilateral cataracts and severe plasma thromboplastin antecedent deficiency (factor XI deficiency). This patient underwent successful cataract extraction in both eyes without complication. The problems inherent in performing eye surgery with factor XI deficiency are discussed.