Benjamin Parrell

Spatiotemporal coupling between speech and manual motor actions

Much evidence has been found for pervasive links between the manual and speech motor systems, including evidence from infant development, deictic pointing, and repetitive tapping and speaking tasks. We expand on the last of these paradigms to look at intra- and cross-modal effects of emphatic stress, as well as the effects of coordination in the absence of explicit rhythm. In this study, subjects repeatedly tapped their finger and synchronously repeated a single spoken syllable. On each trial, subjects placed an emphatic stress on one finger tap or one spoken syllable. Results show that both movement duration and magnitude are affected by emphatic stress regardless of whether that stress is in the same domain (e.g., effects on the oral articulators when a spoken repetition is stressed) or across domains (e.g., effects on the oral articulators when a tap is stressed). Though the size of the effects differs between intra-and cross-domain emphases, the implementation of stress affects both motor domains, indicating a tight connection. This close coupling is seen even in the absence of stress, though it is highlighted under stress. The results of this study support the idea that implementation of prosody is not domain-specific but relies on general aspects of the motor system.

Articulation from acoustics: Estimating constriction degree from the acoustic signal.

Voiced stops in Spanish (/b/, /d/, /g/) are often realized as approximants with incomplete supralaryngeal closure. A number of studies have shown that these are not allophonic variants but rather form part of a continuum of productions, influenced by a number of segmental and prosodic factors. Most work on this topic has used indirect acoustic measurements to estimate articulatory constriction degree. These methods include energy difference in CV (intensity minimum of the consonant over intensity maximum of adjacent vowels), spectral tilt, and maximum rising velocity of the intensity envelope in the CV transition [Kingston, LASP 3, (2008)]. These acoustic measures of constriction, while generally showing the same overall patterns, at times show significant differences in exact results [Hualde et al., LSRL (2010)]. The current study tests the accuracy of all three measures by comparing the acoustic results with articulatorily constriction degree, measured via electromagnetic articulometry (EMA). Comparison...

Evaluation of prosodic juncture strength using functional data analysis.

Prosodic structure has large effects on the temporal realization of speech via the shaping of articulatory events. It is important for speech scientists to be able to systematically quantify these prosodic effects on articulation in a way that is capable both of differentiating between the degree of prosodic lengthening associated with varying linguistic contexts and that is generalizable across speakers. The current paper presents a novel method to automatically quantify boundary strength from articulatory speech data based on functional data analysis (FDA). In particular, a new derived variable-the Deformation Index-is proposed, which is the area under FDA time-deformation functions. First using synthetic speech produced with the TaDA task dynamics computational model, the Deformation Index is shown to be able to capture a priori known differences in boundary strengths instantiated in the π-gesture framework. Additionally, this method accurately distinguishes between types of boundaries in non-synthetic speech produced by four speakers.

Impaired Feedforward Control and Enhanced Feedback Control of Speech in Patients with Cerebellar Degeneration

The cerebellum has been hypothesized to form a crucial part of the speech motor control network. Evidence for this comes from patients with cerebellar damage, who exhibit a variety of speech deficits, as well as imaging studies showing cerebellar activation during speech production in healthy individuals. To date, the precise role of the cerebellum in speech motor control remains unclear, as it has been implicated in both anticipatory (feedforward) and reactive (feedback) control. Here, we assess both anticipatory and reactive aspects of speech motor control, comparing the performance of patients with cerebellar degeneration and matched controls. Experiment 1 tested feedforward control by examining speech adaptation across trials in response to a consistent perturbation of auditory feedback. Experiment 2 tested feedback control, examining online corrections in response to inconsistent perturbations of auditory feedback. Both male and female patients and controls were tested. The patients were impaired in adapting their feedforward control system relative to controls, exhibiting an attenuated anticipatory response to the perturbation. In contrast, the patients produced even larger compensatory responses than controls, suggesting an increased reliance on sensory feedback to guide speech articulation in this population. Together, these results suggest that the cerebellum is crucial for maintaining accurate feedforward control of speech, but relatively uninvolved in feedback control. SIGNIFICANCE STATEMENT Speech motor control is a complex activity that is thought to rely on both predictive, feedforward control as well as reactive, feedback control. While the cerebellum has been shown to be part of the speech motor control network, its functional contribution to feedback and feedforward control remains controversial. Here, we use real-time auditory perturbations of speech to show that patients with cerebellar degeneration are impaired in adapting feedforward control of speech but retain the ability to make online feedback corrections; indeed, the patients show an increased sensitivity to feedback. These results indicate that the cerebellum forms a crucial part of the feedforward control system for speech but is not essential for online, feedback control.

Quantifying prosodic boundary strength using functional data analysis of articulatory movement.

Prosodic boundaries act to locally slow speech, resulting in lengthened articulatory and acoustic durations. The amount of lengthening has been shown to differ based on the juncture strength; however, previous studies disagree on the quantitative characteristics of and qualitative number of prosodic boundaries. Piecewise durational analyzes of articulatory trajectories give only one view of the nature and types of phrasal junctures. Recent work has proposed an alternative to this approach, based on functional data analysis (FDA). [Lee et al., J. Acoust. Soc. Am. (2006).] FDA offers a route to move beyond examining piecewise intervals in the articulatory kinematics, such as constriction duration, to examining the entire time course of a kinematic trajectory to derive a time warping function that characterizes the local non‐linear deformations of articulatory trajectories as a boundary is approached and as it recedes. The use of FDA, and particularly of the deformation index—a measure of local time warping ...

Rate conditioned variability in Western Andalusian Spanish aspiration.

Western Andalusian Spanish normally shows aspiration of /s/ in coda position, but post‐, rather than pre‐, closure aspiration in /s/ + /p,t,k/ sequences. This has been hypothesized to be the result of gestural reorganization, with pre‐closure aspiration the result of anti‐phase coordination and post‐closure the result of in‐phase [Torreira, 9th HLS, 2007]. This experiment explores this hypothesis by leveraging the fact that fast speech can lead to instability in gestural organization and even a spontaneous switch from anti‐ to in‐phase coordination [Turvey, Am. Psych., 1990]. Subjects produced words with the target /s/+/p,t,k/ sequences in time with an acoustic metronome that steadily increased in rate. Results show three patterns of production: consistent preaspiration, consistent postaspiration, and a transition from pre‐ to post‐aspiration as rate increased, corresponding to anti‐phase, in‐phase, and an anti‐ to in‐phase transition, respectively. Excluding the trials with consistent postaspiration, which would not be expected to transition given their stable in‐phase coordination, postaspiration increases as rate increases. If there were no change in gestural coupling, we would expect the opposite pattern: as rate increases, VOT should decrease. The result thus supports the original hypothesis that postaspiration in these sequences is the result of gestural re‐phasing.

How tongue posture differences affect reduction in coronals: Differences between Spanish and English

It has been suggested that both flapping of English coronal stops [e.g. Fukaya & Byrd, JIPA, 2005; De Jong, JPhon, 1998] and spirantization of Spanish voiced stops [e.g. Parrell, LabPhon, 2012] result from reductions in duration. If this is indeed the case, why would reducing duration in one language lead to spirantization (Spanish) and in another to flapping (English)? We suggest that these differences are the result of different ways the tongue is used to attain oral closure in the two languages: in Spanish, coronal stops are made with blade of the tongue at the teeth; in English, with the tongue tip placed at the alveolar ridge. Because of this difference, the tongue tip is oriented differently in the two languages: upward in English and downwards in Spanish, leading to differing articulatory and acoustic outcomes as duration is shortened. We examine these postural differences using tongue movement data, which allows for direct and dynamic examination of tongue posture and shaping of coronals in both l...

Imaging and quantification of glottal kinematics with ultrasound during speech

Most examinations of glottal abduction and adduction during speech have employed laryngoscopic video or transillumination (Hoole, 2006). While these provide accurate information about timing of glottal movements, they are invasive and cannot provide absolute measurements about glottal width. At the same time, recent medical studies have used ultrasonic imaging to accurately capture glottal movements and laryngeal anatomy [Hu, J. Ultrasound Med. (2010); Jadcherla etal., Dysphagia (2006)]. We demonstrate novel methods of using ultrasound to measure both temporal and spatial aspects of glottal movements during speech. While previous work on glottal ultrasound has been limited by the need to manually analyze each acquired frame, we present methods to automatically quantify glottal aperture in ultrasound images. Finally, since glottal ultrasound does not interfere with the acquisition of supra-laryngeal articulatory data, we present the results of preliminary experiments that record laryngeal and supra-larynge...

Explaining Coronal Reduction: Prosodic Structure and Articulatory Posture

Consonant reduction is often treated as an allophonic process at the phonological planning level, with one production target (allophone) being substituted for another. We propose that, alternatively, reduction can be the result of an online process driven by prosodically conditioned durational variability and an invariant production target. We show that this approach can account for patterns of coronal stop (/t/, /d/, and /n/) production in both American English and Spanish. Contrary to effort-driven theories of reduction, we show that reduction does notdepend on changes to gestural stiffness. Moreover, we demonstrate how differences between and within a language in the particular articulatory postures used to produce different coronal stops automatically lead to reduction to what have normally been considered distinct allophones - coronal approximants ([ð̞]) and flaps ([ɾ]). In this way, our approach allows us to understand different outcomes of coronal stop reduction as the dynamic interaction of a single process (durationally driven undershoot) and variable spatial targets. We show that these patterns are reflected across a wide variety of languages, and show how alternative outcomes of reduction may fit within the same general framework.

Articulatory, acoustic, and prosodic accommodation in a cooperative maze navigation task

This study uses a maze navigation task in conjunction with a quasi-scripted, prosodically controlled speech task to examine acoustic and articulatory accommodation in pairs of interacting speakers. The experiment uses a dual electromagnetic articulography set-up to collect synchronized acoustic and articulatory kinematic data from two facing speakers simultaneously. We measure the members of a dyad individually before they interact, while they are interacting in a cooperative task, and again individually after they interact. The design is ideally suited to measure speech convergence, divergence, and persistence effects during and after speaker interaction. This study specifically examines how convergence and divergence effects during a dyadic interaction may be related to prosodically salient positions, such as preceding a phrase boundary. The findings of accommodation in fine-grained prosodic measures illuminate our understanding of how the realization of linguistic phrasal structure is coordinated across interacting speakers. Our findings on individual speaker variability and the time course of accommodation provide novel evidence for accommodation at the level of cognitively specified motor control of individual articulatory gestures. Taken together, these results have implications for understanding the cognitive control of interactional behavior in spoken language communication.