Julie M. Liss

The effects of familiarization on intelligibility and lexical segmentation in hypokinetic and ataxic dysarthria

This study is the third in a series that has explored the source of intelligibility decrement in dysarthria by jointly considering signal characteristics and the cognitive-perceptual processes employed by listeners. A paradigm of lexical boundary error analysis was used to examine this interface by manipulating listener constraints with a brief familiarization procedure. If familiarization allows listeners to extract relevant segmental and suprasegmental information from dysarthric speech, they should obtain higher intelligibility scores than nonfamiliarized listeners, and their lexical boundary error patterns should approximate those obtained in misperceptions of normal speech. Listeners transcribed phrases produced by speakers with either hypokinetic or ataxic dysarthria after being familiarized with other phrases produced by these speakers. Data were compared to those of nonfamiliarized listeners [Liss et al., J. Acoust. Soc. Am. 107, 3415-3424 (2000)]. The familiarized groups obtained higher intelligibility scores than nonfamiliarized groups, and the effects were greater when the dysarthria type of the familiarization procedure matched the dysarthria type of the transcription task. Remarkably, no differences in lexical boundary error patterns were discovered between the familiarized and nonfamiliarized groups. Transcribers of the ataxic speech appeared to have difficulty distinguishing strong and weak syllables in spite of the familiarization. Results suggest that intelligibility decrements arise from the perceptual challenges posed by the degraded segmental and suprasegmental aspects of the signal, but that this type of familiarization process may differentially facilitate mapping segmental information onto existing phonological categories.

Effects of mechanical, cold, gustatory, and combined stimulation to the human anterior faucial pillars

Tactile–Thermal Application (TTA) is a therapy technique designed to enhance the swallowing response in persons with dysphagia. In this study, TTA was broken down into each component stimulus (i.e., Cold, Mechanical, Gustatory), and all combinations thereof, to study the effects of each condition on measurable parameters of the normal human swallow response. Using surface electromyography (EMG), latency to swallow-specific activity and duration of submental EMG activity were measured to examine the following questions: (1) Are there stimulus-dependent differences in onset latencies and contraction durations of the submental muscle activity? (2) Which stimulus components are responsible for this response? (3) How long do the effects of stimulation last on the response? (4) Are there response differences according to age and gender? Between-subjects multivariate analysis of variance showed that the main effects for Treatment, Gender, and Age were significant. Latency to swallow-specific activity was significantly shorter following Mechanical + Cold + Gustatory condition compared to No Stimulation. The effect of stimulation on the swallow response lasted for only one swallow.

Acoustic characteristics of less‐masculine‐sounding male speech

This study compared samples of less-masculine-sounding (LMS) and more-masculine-sounding (MMS) male speech to identify acoustic characteristics, other than fundamental frequency, that might contribute to the perception of these categories. In the first phase, audiorecorded speech samples provided by 35 males were presented to 35 female listeners in a paired-comparison perceptual experiment. Nineteen of the male speech samples were judged reliably to fall within the LMS or MMS categories. Within those 19 samples, 8 speakers (4 LMS and 4 MMS) exhibited similar distributions of habitual fundamental frequency values in connected speech and in sustained phonation. In the second phase of the experiment, various acoustic measures of these eight connected speech samples were conducted. Significant differences between measures of fundamental frequency contours, vowel formant midpoint values, and in the first, third and fourth spectral moments of two fricatives were revealed. These findings may be useful in creating stylized synthetic speech that varies on the dimension of masculinity, and they may have clinical relevance for patients wishing to modify the perception of masculinity invoked by their speech.

On building models of spoken-word recognition: when there is as much to learn from natural "oddities" as artificial normality.

Much of what we know about spoken-word recognition comes from studies relying on speech stimuli either carefully produced in the laboratory or computer altered. Although such stimuli have allowed key constructs to be highlighted, the extent to which these constructs are operative in the processing of everyday speech is unclear. We argue that studying the recognition of naturally occurring degraded speech, such as that produced by individuals with neurological disease, can improve the external validity of existing spoken-word recognition models. This claim is illustrated in an experiment on the effect of talker-specific (indexical) variations on lexical access. We found that talker specificity effects, wherein words are better recalled if played in the same voice than in a different voice between two consecutive blocks, were greater when the words were spoken by dysarthric than by healthy individuals. The effects were found to relate to the increased processing time caused by the dysarthric stimuli, independently of their reduced intelligibility. This result is consistent with Luce, McLennan, and Charles-Luces (2003) time-course hypothesis, which posits that reliance on indexical details increases when responses are delayed by suboptimal processing conditions. We conclude by advocating the use of laboratory and naturally occurring degraded speech in tandem and more systematic cross-talks between psycholinguistics and the speech sciences.

The use of fundamental frequency for lexical segmentation in listeners with cochlear implants

Fundamental frequency (F0) variation is one of a number of acoustic cues normal hearing listeners use for guiding lexical segmentation of degraded speech. This study examined whether F0 contour facilitates lexical segmentation by listeners fitted with cochlear implants (CIs). Lexical boundary error patterns elicited under unaltered and flattened F0 conditions were compared across three groups: listeners with conventional CI, listeners with CI and preserved low-frequency acoustic hearing, and normal hearing listeners subjected to CI simulations. Results indicate that all groups attended to syllabic stress cues to guide lexical segmentation, and that F0 contours facilitated performance for listeners with low-frequency hearing.

The Influence of Familiarity on Judgments of Treated Speech

Three groups of 10 naive listeners transcribed sentences produced by a dysarthric speaker. The first group (Control) transcribed sentences that the speaker read in her customary manner. A second gr...

Familiarisation conditions and the mechanisms that underlie improved recognition of dysarthric speech

This investigation evaluated the familiarisation conditions required to promote subsequent and more long-term improvements in perceptual processing of dysarthric speech and examined the cognitive-perceptual processes that may underlie the experience-evoked learning response. Sixty listeners were randomly allocated to one of three experimental groups and were familiarised under the following conditions: (1) neurologically intact speech (control), (2) dysarthric speech (passive familiarisation), and (3) dysarthric speech coupled with written information (explicit familiarisation). All listeners completed an identical phrase transcription task immediately following familiarisation, and listeners familiarised with dysarthric speech also completed a follow-up phrase transcription task 7 days later. Listener transcripts were analysed for a measure of intelligibility (percent words correct), as well as error patterns at a segmental (percent syllable resemblance) and suprasegmental (lexical boundary errors) level of perceptual processing. The study found that intelligibility scores for listeners familiarised with dysarthric speech were significantly greater than those of the control group, with the greatest and most robust gains afforded by the explicit familiarisation condition. Relative perceptual gains in detecting phonetic and prosodic aspects of the signal varied dependent upon the familiarisation conditions, suggesting that passive familiarisation may recruit a different learning mechanism to that of a more explicit familiarisation experience involving supplementary written information. It appears that decisions regarding resource allocation during subsequent processing of dysarthric speech may be informed by the information afforded by the conditions of familiarisation.

Tracking Discourse Complexity Preceding Alzheimer's Disease Diagnosis: A Case Study Comparing the Press Conferences of Presidents Ronald Reagan and George Herbert Walker Bush

Changes in some lexical features of language have been associated with the onset and progression of Alzheimers disease. Here we describe a method to extract key features from discourse transcripts, which we evaluated on non-scripted news conferences from President Ronald Reagan, who was diagnosed with Alzheimers disease in 1994, and President George Herbert Walker Bush, who has no known diagnosis of Alzheimers disease. Key word counts previously associated with cognitive decline in Alzheimers disease were extracted and regression analyses were conducted. President Reagan showed a significant reduction in the number of unique words over time and a significant increase in conversational fillers and non-specific nouns over time. There was no significant trend in these features for President Bush.

Automatic assessment of vowel space area.

Vowel space area (VSA) is an attractive metric for the study of speech production deficits and reductions in intelligibility, in addition to the traditional study of vowel distinctiveness. Traditional VSA estimates are not currently sufficiently sensitive to map to production deficits. The present report describes an automated algorithm using healthy, connected speech rather than single syllables and estimates the entire vowel working space rather than corner vowels. Analyses reveal a strong correlation between the traditional VSA and automated estimates. When the two methods diverge, the automated method seems to provide a more accurate area since it accounts for all vowels.

Rhythm as a Coordinating Device: Entrainment With Disordered Speech

PURPOSE The rhythmic entrainment (coordination) of behavior during human interaction is a powerful phenomenon, considered essential for successful communication, supporting social and emotional connection, and facilitating sense-making and information exchange. Disruption in entrainment likely occurs in conversations involving those with speech and language impairment, but its contribution to communication disorders has not been defined. As a first step to exploring this phenomenon in clinical populations, the present investigation examined the influence of disordered speech on the speech production properties of healthy interactants. METHOD Twenty-nine neurologically healthy interactants participated in a quasi-conversational paradigm, in which they read sentences (response) in response to hearing prerecorded sentences (exposure) from speakers with dysarthria (n = 4) and healthy controls (n = 4). Recordings of read sentences prior to the task were also collected (habitual). RESULTS Findings revealed that interactants modified their speaking rate and pitch variation to align more closely with the disordered speech. Production shifts in these rhythmic properties, however, remained significantly different from corresponding properties in dysarthric speech. CONCLUSION Entrainment offers a new avenue for exploring speech and language impairment, addressing a communication process not currently explained by existing frameworks. This article offers direction for advancing this line of inquiry.