Dani Byrd

Auditory Selective Attention: An fMRI Investigation

In the present experiment, 25 adult subjects discriminated speech tokens ([ba]/[da]) or made pitch judgments on tone stimuli (rising/falling) under both binaural and dichotic listening conditions. We observed that when listeners performed tasks under the dichotic conditions, during which greater demands are made on auditory selective attention, activation within the posterior (parietal) attention system and at primary processing sites in the superior temporal and inferior frontal regions was increased. The cingulate gyrus within the anterior attention system was not influenced by this manipulation. Hemispheric differences between speech and nonspeech tasks were also observed, both at Brocas Area within the inferior frontal gyrus and in the middle temporal gyrus.

An approach to real‐time magnetic resonance imaging for speech production

Magnetic resonance imaging (MRI) has served as a valuable tool for studying static postures in speech production. Now, recent improvements in temporal resolution are making it possible to examine the dynamics of vocal-tract shaping during fluent speech using MRI. The present study uses spiral k-space acquisitions with a low flip-angle gradient echo pulse sequence on a conventional GE Signa 1.5-T CV/i scanner. This strategy allows for acquisition rates of 8-9 images per second and reconstruction rates of 20-24 images per second, making veridical movies of speech production now possible. Segmental durations, positions, and interarticulator timing can all be quantitatively evaluated. Data show clear real-time movements of the lips, tongue, and velum. Sample movies and data analysis strategies are presented.

The elastic phrase: modeling the dynamics of boundary-adjacent lengthening

This work examines the relation between phrasal structure and the control and coordination of articulation within a dynamical systems model of speech production. In this context, we review how speakers modulate the spatiotemporal organization of articulatorygestures as a function of their phrasal position. We present computational simulations that capture several important qualitative properties of these phrase boundaryeffects, such as prosodically -induced local slowing. This slowing is generated by dynamical effects on the activation timecourse of articulatory gestures and is controlled by prosodic gestures or p-gestures, which share much with the familiar dynamical description of constriction gestures. Prosodic gestures, however, function at boundaries purelyto temporallystretch or shrink gestural activation trajectories. This modulation of the ‘‘clock-rate’’ that controls the temporal unfolding of an utterance near junctures is such that the clock slows increasinglyas the boundaryis approached and speeds up again as the boundaryrecedes. Viewing phrase boundaries as warping the temporal fabric of an utterance represents a promising confluence of the fields of prosodyand of speech dy namics. r 2003 Elsevier Science Ltd. All rights reserved.

Action to Language via the Mirror Neuron System: The role of vocal tract gestural action units in understanding the evolution of phonology

Language can be viewed as a structuring of cognitive units that can be transmitted among individuals for the purpose of communicating information. Cognitive units stand in specific and systematic relationships with one another, and linguists are interested in the characterization of these units and the nature of these relationships. Both can be examined at various levels of granularity. It has long been observed that languages exhibit distinct patterning of units in syntax and in phonology. This distinction, a universal characteristic of language, is termed duality of patterning (Hockett, 1960). Syntax refers to the structuring of words in sequence via hierarchical organization, where words are meaningful units belonging to an infinitely expandable set. But words also are composed of structured cognitive units. Phonology structures a small, closed set of recombinable, non-meaningful units that compose words (or signs, in the case of signed languages). It is precisely the use of a set of non-meaningful arbitrary discrete units that allows word creation to be productive. 1 In this chapter we outline a proposal that views the evolution of syntax and of phonology as arising from different sources and ultimately converging in a symbiotic relationship. Duality of patterning forms the intellectual basis for this proposal. Grasp and other manual gestures in early hominids are, as Arbib (Chapter 1, this volume) notes, well suited to provide a link from the iconic to the symbolic. Critically, the iconic aspects of manual gestures lend them a meaningful aspect that is critical to evolution of a system of symbolic units. However, we will argue that, given duality of patterning, phonological evolution crucially requires the emergence of effectively non-meaningful combinatorial units. We suggest that vocal tract action gestures are well suited to play a direct role in phonological evolution because, as argued by Studdert-Kennedy (2002a), they are

Articulatory Vowel Lengthening and Coordination at Phrasal Junctures

Recent work has demonstrated that progressively stronger prosodic boundaries result in increasing amounts of lengthening for consonant gestures, both preceding and following the boundary. The present experiment extends these earlier findings by considering kinematic data collected with a magnetometer to determine (1) if vocalic gestures demonstrate lengthening patterns comparable to those of consonantal gestures due to adjacent prosodic boundaries, and (2) if the relative timing of consonant and vowel gestures is affected by adjacent boundaries. A magnetometer system was used to track articulator movements of 3 speakers producing sentences in which a /...C1V1(#)C2V2.../ sequence was embedded with varying medial boundaries. All subjects demonstrated lengthening of the vocalic articulation before stronger boundaries. Additionally, effects on the relative timing of words spanning a boundary and the relative timing of segments in boundary-adjacent syllables were observed.

Task-dynamics of gestural timing: Phase windows and multifrequency rhythms

Abstract In this paper, we explore the hypothesis that intergestural phasing relations are implemented via coupling terms in a nonlinear dynamical systems model. Specifically, we describe recent computational developments of the task-dynamic model of gestural patterning (e.g., E. Saltzman, J. A. S. Kelso, Psychological Review 94 (1987) 84–106; E. Saltzman, K. G. Munhall, Ecological Psychology 1 (1989) 333–382) that are focused on modeling the timing of rhythmic action units. First, we explore the possibility of attractor states for intergestural phasing that are characterized as ranges or phase windows (D. Byrd, Phonology 13 (1996) 139–169), and contrast this behavior with standard models that display punctate relative phasing. It is argued that the phase window approach can provide flexible control of the relative timing of articulatory gestures, allowing constrained variability in intergestural timing as a function of linguistic and para-linguistic factors. Second, we discuss how this extension of the task-dynamic model has been adapted for modeling the production of multifrequency rhythms (speech or bimanual). This work explores the control of the frequency- and phase-locking characteristics of coupled limit cycle oscillators by examining how desired frequency ratio, intrinsic frequency detuning, and coupling asymmetries interact in creating observed rhythmic patterns. Using this method, details of the resultant transient and steady-state trajectories of phase and amplitude are generated that are not available using models derived with averaging techniques.

How far, how long: On the temporal scope of prosodic boundary effects

Acoustic lengthening at prosodic boundaries is well explored, and the articulatory bases for this lengthening are becoming better understood. However, the temporal scope of prosodic boundary effects has not been examined in the articulatory domain. The few acoustic studies examining the distribution of lengthening indicate that boundary effects extend from one to three syllables before the boundary, and that effects diminish as distance from the boundary increases. This diminishment is consistent with the pi-gesture model of prosodic influence [Byrd and Saltzman, J. Phonetics 31, 149-180 (2003)]. The present experiment tests the preboundary and postboundary scope of articulatory lengthening at an intonational phrase boundary. Movement-tracking data are used to evaluate durations of consonant closing and opening movements, acceleration durations, and consonant spatial magnitude. Results indicate that prosodic boundary effects exist locally near the phrase boundary in both directions, diminishing in magnitude more remotely for those subjects who exhibit extended effects. Small postboundary effects that are compensatory in direction are also observed.

Preliminary results on speaker-dependent variation in the TIMIT database.

A set of phonetic studies based on analysis of the TIMIT speech database is presented. Using a database methodological approach, these studies detail new results in speaker-dependent variation due to sex and dialect region of the talker including effects on stop release frequency, speaking rate, vowel reduction, flapping, and the use of glottal stop. TIMIT was found to be fertile ground for gathering acoustic-phonetic knowledge having relevance to the phonetic classification and recognition goals for which TIMIT was designed, as well as to the linguist attempting to describe regularity and variability in the pronunciation of read English speech.

C-centers revisited

This report considers the articulatory organization of English consonant sequences with their adjacent vowels. Electropal-atography is used to examine the production of sequences of one to four consonants in length. Two aspects of the production of consonant sequences are investigated. First, the phenomenon of compensatory shortening is addressed. Second, the evidence for a global timing organization for consonant sequences is investigated. This experiment evaluates predictions of Browman and Goldstein [1988] regarding the significance of the C-center in the timing of consonant sequences. Some support for global timing relationships is found; however, underlying syllable affiliations are suggested to be important in the selection of timing arrangements.

Timing effects of syllable structure and stress on nasals: a real-time MRI examination.

The coordination of velum and oral gestures for English [n] is studied using real-time MRI movies to reconstruct vocal tract aperture functions. This technique allows for the examination of parts of the vocal tract otherwise inaccessible to dynamic imaging or movement tracking. The present experiment considers syllable onset, coda, and juncture geminate nasals and also addresses the effects of a variety of word stress patterns on segment internal coordination. We find a bimodal timing pattern in which near-synchrony of velum lowering and tongue tip raising characterizes the timing for onsets and temporal lag between the gestures is characteristic for codas, supporting and extending the findings of Krakow (1989), 1993) for [m]. Intervocalic word-internal nasals are found to have timing patterns that are sensitive to the local stress context, which suggests the presence of an underlying timing specification that can yield flexibly. We consider these findings in light of the gestural coupling structures described by Goldstein and colleagues (Goldstein, Byrd, & Saltzman 2006; Nam, Goldstein, and Saltzman in press; Goldstein, Nam, Saltzman, & Chitoran 2008).