Biomedical subjects

K Tjaden

Publications and source records attributed to K Tjaden.

9 recordsLinked to original sources

PubMed2000

Segmental timing in amyotrophic lateral sclerosis.

This study describes segmental timing patterns for a passage read by speakers with ALS and a group of age- and gender-matched neurologically healthy speakers. Segment durations for ALS speakers' habitual rates (ALS condition) were compared to segment durations for healthy speakers' habitual and slow reading rates (Control Habitual and Control Slow conditions). Temporal differences for pairs of sound classes (i.e., long-short vowels, voiceless-voiced fricatives, voiceless-voiced stop gaps, high-low vowels) and prepausal lengthening of vowels also were studied. The results of the ALS-Control Habitual comparison suggested that the slowed articulatory rate of ALS influences segmental timing for most phonetic events. The finding that local segmental cues for disordered speakers were broadly consistent with their overall (slow) articulatory rate suggests that duration likely does not contribute in a significant way to intelligibility deficits in ALS. A qualitative analysis further indicated that the slowed rate of ALS is not uniformly distributed across phonetic events, but influences segment durations of particular sound categories in ways consistent with the disease process. The analysis comparing segment durations for the ALS and Control Slow conditions suggested that the overall pattern of segmental timing for speakers with ALS was broadly similar to the pattern for voluntarily slowed speech of healthy talkers. Finally, temporal differences for sound classes (i.e., voiceless-voiced fricatives, long-short vowels) and prepausal lengthening for speakers with ALS typically were similar to healthy speakers' habitual and slow speech. There were substantial variability within speaker groups and reversals of expected effects, however. The implication is that temporal differences for sound classes, such as short and long vowels, are not a particularly reliable perceptual cue for listeners.

Adult↗

PubMed2000

Acoustic differences between content and function words in amyotrophic lateral sclerosis.

Studies describing acoustic characteristics of speech produced by individuals with dysarthria may help to explain intelligibility deficits for these speakers. One goal of the current study was to investigate the manner and extent to which nine speakers with mild to moderate dysarthria associated with amyotrophic lateral sclerosis (ALS) and nine healthy speakers acoustically distinguished /i/, /ae/, /u/, and /a/ in content and function words. A further aim was to evaluate the relationship between impaired speech in ALS and the magnitude of acoustic differences for vowels in content and function words. Speakers read the Farm Passage at a comfortable or habitual rate. F1 and F2 midpoint frequencies were measured, and vowel space areas were calculated. Vowel durations also were measured. The magnitude of F1, F2, vowel space area, and duration differences for vowels in content and function words was not statistically different for speakers with ALS and healthy controls. In addition, with the exception of /i/ produced by some speakers with ALS, vowel duration tended to be shorter in function words. Average F1 and F2 values for function words also tended to be centralized relative to content words. Although vowel space area differences for the two speaker groups were not statistically significant, there was a tendency for the difference in vowel space area for content and function words to be smaller for speakers with ALS than for controls. Regression analyses further indicated that the magnitude of temporal differences for vowels in content and function words was a better predictor of impaired speech than the magnitude of spectral differences for vowels in content and function words. One clinical implication is that individuals with ALS may benefit from therapy techniques targeting temporal properties of the acoustic signal.

Adult↗

PubMed2000

A preliminary study of factors influencing perception of articulatory rate in Parkinson disease.

This investigation was a preliminary study of factors influencing perception of articulatory rate in idiopathic Parkinson disease (PD). Nine men with mild to moderate idiopathic PD and 9 healthy men of a similar age read the Farm Passage at habitual, fast, and slow reading rates. Spontaneous speech samples also were obtained. Speech severity for participants with PD was mild to moderate; prominent perceptual characteristics further suggested hypokinetic dysarthria. Nine listeners estimated the articulatory rate of speech runs (i.e., stretch of speech bounded by pauses) extracted from the reading and spontaneous speech samples. Regression analysis was used to explore the relationship between articulatory rate (i.e., syllables produced per second excluding pauses) and perceptual impressions of articulatory rate as well as the relationship between fundamental frequency (F0) range and perceptual estimates of articulatory rate. Regression functions predicting perceptual estimates of articulatory rate from F0 range were not significant for either speaker group. The regression analyses relating articulatory rate and perceptual estimates of articulatory rate, however, revealed a significant, positive relationship between the two measures for both speaker groups. There also was a nonsignificant trend for perception of articulatory rate to grow more rapidly for Parkinsonian speech samples. Although the current findings should be interpreted with caution until they have been validated by additional studies using much larger speaker populations and more extensive speech samples, the results hint at the possibility that perceptual impressions of articulatory rate in PD may overestimate the actual, physical rate. The results also highlight the importance of speech-language pathologists complimenting perceptual judgements of articulatory rate with physical measures.

Aged↗

PubMed2000

An acoustic study of coarticulation in dysarthric speakers with Parkinson disease.

Anticipatory vowel coarticulation in obstruent + vowel syllables was studied for 9 dysarthric males with mild to moderate idiopathic Parkinson disease (PD) and a group of 10 healthy males. In addition to studying coarticulatory differences for speakers' habitual rate repetitions, a graded speaking rate task was used to investigate the effect of rate variation on coarticulation. The ratio of F2 onset frequency/F2 target frequency was used to infer coarticulation (i.e., ratios of 1.0 indicate complete vowel harmony at vowel onset, and ratios greater than 1.0 indicate relatively less coarticulation). Because F2 onset frequency is a relatively novel measure of coarticulation, a more common measure of anticipatory vowel coarticulation-fricative F2-was obtained for a subset of the speech stimuli and compared to F2 onset measures. Ratios of fricative F2/F2 target frequency also were computed to infer coarticulation and the results were compared to the F2 onset/F2 target ratios. The results indicated a modest relationship between F2 onset frequency and fricative F2 for both speaking tasks and speaker groups, with a stronger relationship for the graded rate task. Regression analyses for the graded rate task further indicated that longer vowel durations were associated with larger ratios for both speaker groups. Thus, coarticulation tended to increase with faster rates and decrease with slower rates, although the relationship was more systematic for control speakers. Ratios for the habitual task tended to be smaller for speakers with PD, suggesting increased coarticulation relative to control speakers. This effect was not entirely attributable to the more rapid speaking rates for speakers with PD. Because habitual rate F2 onset/F2 target ratios tended to underestimate the extent to which coarticulation was increased for speakers with PD-compared to the fricative F2/F2 target ratios-measures other than F2 onset should be used to infer absolute differences in extent of coarticulation for speakers with PD and healthy controls.

Aged↗

PubMed1999

Can a model of overlapping gestures account for scanning speech patterns?

A simple acoustic model of overlapping, sliding gestures was used to evaluate whether coproduction was reduced for neurologic speakers with scanning speech patterns. F2 onset frequency was used as an acoustic measure of coproduction or gesture overlap. The effects of speaking rate (habitual versus fast) and utterance position (initial versus medial) on F2 frequency, and presumably gesture overlap, were examined. Regression analyses also were used to evaluate the extent to which across-repetition temporal variability in F2 trajectories could be explained as variation in coproduction for consonants and vowels. The lower F2 onset frequencies for disordered speakers suggested that gesture overlap was reduced for neurologic individuals with scanning speech. Speaking rate change did not influence F2 onset frequencies, and presumably gesture overlap, for healthy or disordered speakers. F2 onset frequency differences for utterance-initial and -medial repetitions were interpreted to suggest reduced coproduction for the utterance-initial position. The utterance-position effects on F2 onset frequency, however, likely were complicated by position-related differences in articulatory scaling. The results of the regression analysis indicated that gesture sliding accounts, in part, for temporal variability in F2 trajectories. Taken together, the results of this study provide support for the idea that speech production theory for healthy talkers helps to account for disordered speech production.

Adult↗

PubMed1998

Speaking-rate-induced variability in F2 trajectories.

This study examined speaking-rate-induced spectral and temporal variability of F2 formant trajectories for target words produced in a carrier phrase at speaking rates ranging from fast to slow. F2 onset frequency measured at the first glottal pulse following the stop consonant release in target words was used to quantify the extent to which adjacent consonantal and vocalic gestures overlapped; F2 target frequency was operationally defined as the first occurrence of a frequency minimum or maximum following F2 onset frequency. Regression analyses indicated 70% of functions relating F2 onset and vowel duration were statistically significant. The strength of the effect was variable, however, and the direction of significant functions often differed from that predicted by a simple model of overlapping, sliding gestures. Results of a partial correlation analysis examining interrelationships among F2 onset, F2 target frequency, and vowel duration across the speaking rate range indicated that covariation of F2 target with vowel duration may obscure the relationship between F2 onset and vowel duration across rate. The results further suggested that a sliding based model of acoustic variability associated with speaking rate change only partially accounts for the present data, and that such a view accounts for some speakers' data better than others.

Female↗

PubMed1997

Spectral properties of fricatives in amyotrophic lateral sclerosis.

Spectral characteristics of word initial /s/ and "sh" produced by individuals with amyotrophic lateral sclerosis (ALS) and healthy controls were quantified using spectral moment analysis. Coefficients of the first four moments were used as descriptive indices of central tendency, spread of energy, shape, and peakedness. The relationship between select moment coefficients and consonant precision ratings was investigated to explore potential perceptual correlates of the acoustic measures. To examine whether spectra for ALS and healthy speakers were influenced similarly by context, first moment coefficients for three occurrences of /s/ in "some" were inspected for individual speakers. Select moment coefficients also were compared to hand-derived spectral measures for a subset of speakers. Results suggest articulatory differences in /s/ and "sh" for the present group of ALS speakers and healthy controls, as indexed by between-group differences in first moment coefficients. A linear function accounted for a significant proportion of the variance in the relationship between consonant precision ratings and the frequency difference between the first moment for /s/ and "sh". Inspection of first moment coefficients for multiple occurrences of /s/ in "some" suggests context influences the first moment in a similar manner for ALS and healthy speakers. The subanalysis comparing moment coefficients and hand-derived spectral measures revealed both similarities and differences in the manner the two measurement techniques reflect spectral shape.

Adult↗

PubMed1995

The influence of speaking rate on vowel space and speech intelligibility for individuals with amyotrophic lateral sclerosis.

The relationship between speaking rate, vowel space area, and speech intelligibility was studied in a group of 9 subjects with amyotrophic lateral sclerosis (ALS) and 9 age- and gender-matched controls. Subjects read a standard passage (the Farm Passage) at three speaking rates, including HABITUAL, FAST, and SLOW. Vowel segment durations and target formant frequencies were measured at each speaking rate from select words containing the vowels /i/, /ae/, /a/, and /u/. To quantify changes in vowel space area across speaking rate, the area of the vowel quadrilateral was calculated for each speaker at each speaking rate. In addition, intelligibility estimates at each speaking rate were obtained for the dysarthric speakers. Results revealed that dysarthric speakers exhibited smaller vowel space areas and less systematic changes in vowel space as a function of speaking rate, when compared to the neurologically intact speakers. In an examination of the relationship between vowel space area and speech intelligibility, vowel space was found to account for 45% of the variance in speech intelligibility. This result suggests that vowel space area is an important component of global estimates of speech intelligibility.

Adult↗

PubMedDate not supplied

Stress-induced variation in F2 trajectories as evidence for coproduction in CV syllables.

This study explored the extent to which a model of the acoustic consequences of overlapping, sliding consonantal and vocalic gestures was used to account for stress-induced changes in F2 trajectories occurring in test words embedded in a carrier phrase. Three stress conditions were studied including contrastive stress on test words (CS), contrastive stress on the content word preceding test words (U-CS), and non contrastive stress on test words (NS). F2 onset frequency was used to quantify the extent to which adjacent consonantal and vocalic gestures in stop consonant + vowel syllables were coproduced (i.e., overlapped) in the different stress conditions. The predicted relationship between F2 onset frequency and temporal variation in trajectories was also examined within and across stress conditions. In addition, the effects of stress-induced variation in articulatory scaling on F2 onset frequency were studied and factored into the interpretation of the results. The results indicated that F2 onset frequencies tended to differ for stress conditions characterized by large differences in prominence. Regression analyses predicting temporal variation in trajectories from F2 onset frequency accounted for part of the variance within and across stress conditions. Taken together, the results suggested that a model of overlapping, sliding gestures accounts for only some of the stress-induced variability in F2 trajectories in the current study.

Adult↗