Influence of the Covering Area of Major Connectors of Mandibular Dentures on the Accuracy of Speech Production: A Pilot Study

<b><i>Background/Objectives:</i></b> Speech impairment during the initial phase of removable partial denture (RPD) treatment can prevent patient adaptation to RPDs. This quasi-experimental study aimed to investigate the influence of the covering area of major connectors located in the mandibular anterior region on the accuracy of speech production. <b><i>Methods:</i></b> Fifteen adults (12 men and 3 women aged 26–40 years) with healthy dentition were recruited. Four target syllables were used for the assessments: [ʃi], [ʧi], [çi], and [ki]. There were four speaking conditions: without a connector (control), wearing lingual bar (5 mm width), wearing lingual plates (12 mm width), and wearing connectors covering the occlusal surface of lower dentition (16 mm width; CO). The accuracy of speech production was evaluated by mean appearance ratio of correct labels (MARC) and incorrect labels (MARIC) of the phonetic segments which were calculated with a speech evaluation system (VoiceAnalyzer). <b><i>Results:</i></b> The MARC in the 3 target syllables [ʃi], [ʧi], and [ki] significantly decreased with CO. For the target syllable [ʃi], the MARICs of [ʧi], [ʤi], and [çi] with CO were significantly lower than that in the control. For the target syllable [ʧi], the MARIC of [ki] with CO was significantly higher than that in the control. For the target syllable [çi], the MARIC of [gi] with CO was significantly higher than that in the control. <b><i>Conclusion:</i></b> RPDs with major connectors covering the lower dentition could disturb speech production during the initial phase of RPD treatment. Prosthodontic treatment with such RPD designs requires further consideration regarding the information given to patients before starting the treatment.

The influence of lexical status and neighborhood density on children's nonword repetition

ABSTRACTThis study examined effects of lexical status and neighborhood density of constituent syllables on children's nonword repetition and interactions with nonword length. Lexical status of the target syllable impacted repetition accuracy for the longest nonwords. In addition, children made more errors that changed a nonword syllable to a word syllable than the reverse. Syllables from dense versus sparse neighborhoods were repeated more accurately in three- and four-syllable nonwords, but there was no effect of density for two-syllable nonwords. The effect of neighborhood density was greater for a low versus high vocabulary group. Finally, children's error responses were from more dense neighborhoods than the target syllables. The results are congruent with models of nonword repetition that emphasize the influence of long-term lexical knowledge on children's performance.

The Process of Syllable Acquisition in Adult Indigo Buntings (Passerina Cyanea)

Vocal learning in adult indigo buntings was studied by monitoring socially paired males housed together in sound isolation boxes. Two of three yearlings socially paired with older birds in early spring acquired new syllables and reorganized their stereotyped and plastic songs, while eleven yearlings socially paired later in the year largely failed to acquire new material, as did the older adults socially paired at various times of year. Yearlings changed their stereotyped songs to more closely match their tutors' by replacing syllables or by inserting new syllables. This song matching involved two processes in which adult plastic song played a role: (1) new syllables were developed in plastic song, and (2) newly mastered or pre-existing syllables were transferred from plastic song into stereotyped song. Morphological similarity between yearlings' and tutors' syllables strongly influenced which syllables yearlings retained. After social pairing, matching syllables tended to be delivered more frequently by yearlings and become incorporated into their stereotyped songs, while non-matching syllables tended to decline in use or be discarded altogether. New syllables were formed from existing syllables most morphologically similar to the "target" syllable, through transformation and combination of existing syllables. As new forms became more common, old forms declined and eventually were discarded. Our data suggest that adult indigo buntings maintain the ability to sing stereotyped songs while new material is mastered, and held in reserve, in plastic song. Acquisition of new syllables in yearling indigo buntings requires trial-and-error learning, but proceeds without overproduction and subsequent attrition of distinct syllable types, and does not substantially rely on improvisation and invention. Rather, syllable acquisition and changes to stereotyped songs are strongly influenced by the pre-existing syllable repertoire.

Stimulus-Dependent Ear Asymmetry in a Dichotic Monitoring Task

Auditory lateralization was investigated in 26 right-handed and 26 left-handed, normal subjects using two dichotic monitoring tasks in each proband [dichotic consonant-vowel (CV) syllable monitoring once with the syllable /ta/ and once with the syllable /da/ as target]. Subjects were instructed to monitor for the presence of a target CV which could occur in either ear. They responded by depressing a response button; reaction time (RT) and hit rates were recorded. In right-handers the syllable /ta/ presented to the right ear was detected more frequently, on the average, than presented to the left ear. Also, RT was shorter for detection of /ta/ in the right ear than for detection in the left ear for both right- and left-handers. The detection of /da/ showed no ear advantage in hit rate and RT either for right-handers or for left-handers. These results demonstrate the existence of a right-ear advantage in dichotic monitoring of the target syllable /ta/ but not for the target syllable /da/. This difference in evoking a right-ear advantage is attributed to a difference in the difficulty of detection of both targets. It is argued that the detection of /da/ is too difficult to evoke phonetic processing, leading to a right-ear advantage.

Relationships between the Perception of Nasalization and Speech Movements in Speakers with Cleft Palate

The purpose of this study was to examine the relationships between several temporal measures of speech movements and perceived nasalization in speakers with cleft palate. Four adult subjects with repaired cleft palate were filmed using high-speed (100 frames/s) cinefluorography as they produced target syllables embedded in a carrier phrase. Perceived nasalization of each extracted acoustic target syllable was rated by 18 trained judges. Movements of the tongue tip, tongue dorsum, jaw, velar knee, velar tip, and posterior pharyngeal wall were plotted over time. Time of movement onsets and movement offsets was identified from the plots. Voice onset and offset times were identified from the synchronized acoustic recordings. The findings indicate that normally expected velopharyngeal movements occurred near the time of jaw-lowering onset during nasalized CVC and CVN productions in two subjects who were judged to exhibit high levels of nasalization. The other two subjects showed no velopharyngeal movements during the CVC production. It is speculated that velopharyngeal movements normally expected in CVC utterances may be avoided by some speakers with cleft palate in order to minimize perceptible nasalization.

Dichotic Backward Masking of Complex Sounds

In the first experiment subjects identified a consonant-vowel syllable presented dichotically with a known contralateral masking sound at a stimulus onset asynchrony of ± 60 msec. When the mask followed the target syllable, perception of place of articulation of the consonant was impaired more when the mask was a different consonant-vowel syllable than when it was either a steady-state vowel or a non-speech timbre. Perception was disturbed less when the mask preceded the target, and the amount of disruption was independent of which mask was used. Greater backward than forward masking was also found in the second experiment for the identification of complex sounds which differed in an initial change in pitch. These experiments suggest that the extraction of complex auditory features from a target can be disrupted by the subsequent contralateral presentation of a sound sharing certain features with the target.