Antoine Serrurier

A three-dimensional articulatory model of the velum and nasopharyngeal wall based on MRI and CT data

An original three-dimensional (3D) linear articulatory model of the velum and nasopharyngeal wall has been developed from magnetic resonance imaging (MRI) and computed tomography images of a French subject sustaining a set of 46 articulations, covering his articulatory repertoire. The velum and nasopharyngeal wall are represented by generic surface triangular meshes fitted to the 3D contours extracted from MRI for each articulation. Two degrees of freedom were uncovered by principal component analysis: first, VL accounts for 83% of the velum variance, corresponding to an oblique vertical movement seemingly related to the levator veli palatini muscle; second, VS explains another 6% of the velum variance, controlling a mostly horizontal movement possibly related to the sphincter action of the superior pharyngeal constrictor. The nasopharyngeal wall is also controlled by VL for 47% of its variance. Electromagnetic articulographic data recorded on the velum fitted these parameters exactly, and may serve to recover dynamic velum 3D shapes. The main oral and nasopharyngeal area functions controlled by the articulatory model, complemented by the area functions derived from the complex geometry of each nasal passage extracted from coronal MRIs, were fed to an acoustic model and gave promising results about the influence of velum movements on the spectral characteristics of nasals.

Articulatory capacity of Neanderthals, a very recent and human-like fossil hominin

Scientists seek to use fossil and archaeological evidence to constrain models of the coevolution of human language and tool use. We focus on Neanderthals, for whom indirect evidence from tool use and ancient DNA appears consistent with an adaptation to complex vocal-auditory communication. We summarize existing arguments that the articulatory apparatus for speech had not yet come under intense positive selection pressure in Neanderthals, and we outline some recent evidence and analyses that challenge such arguments. We then provide new anatomical results from our own attempt to reconstruct vocal tract (VT) morphology in Neanderthals, and document our simulations of the acoustic and articulatory potential of this reconstructed Neanderthal VT. Our purpose in this paper is not to polarize debate about whether or not Neanderthals were human-like in all relevant respects, but to contribute to the development of methods that can be used to make further incremental advances in our understanding of the evolution of speech based on fossil and archaeological evidence.

3D-MORPHOMETRIC AND ACOUSTIC ANALYSIS OF CHIMPANZEE AND HUMAN VOCAL TRACTS, AND THEIR USE IN THE RECONSTRUCTION OF NEANDERTHAL VOCAL TRACTS AND THEIR ACOUSTIC POTENTIAL

We obtained CT-scans of an ontogenetic series of chimpanzee cadavers from the Zurich Anthropology Institute collections, and isolated their vocal tracts for morphological analysis and acoustic/articulatory modelling. We analysed these vocal tracts in three dimensions, and identified a set of anatomical features that define characteristic constrictions and expansions along their lengths. Acoustic modelling of these tracts in a multi-tube configuration (which best approximated the observed morphology) enabled us to predict their passive or resting-state acoustic potential, and also enabled us to digitally perturb this resting-state configuration to explore their phonetic potential in relation to the human vowel triangle. We will compare our anatomical results with those of Nishimura (e.g. 2005), and our acoustic results with those of Lieberman, Crelin and Klatt (1972).

PRODUCTION OF THE VOWELS / a i u/ BASED ON AN ARTICULATORY MODEL OF FEEDING

Both ontogenetically and phylogenetically feeding tasks precede speaking tasks, two of the major functions of the human vocal tract (VT). Researchers have therefore suggested that speech cyclicity, in particular tongue movements, derives from feeding cyclicity (MacNeilage, 1998; Hiiemae and Palmer 2003). Our study explores this hypothesis using articulatory modelling to determine if the tongue movements in speech are a subset of those in feeding. In a previous study (Serrurier et al., 2008) we used ElectroMagnetic Articulography, however this is an invasive technique that further gives no VT boundaries. To overcome these limitations we here use Digital VideoFluoroscopy (DVF). We wish to explore if we can extract from the raw data and from an articulatory model based on the data, articulations which are geometrically and acoustically close to the quantal vowels /a i u/. Their typical F1-F2 values and their typical geometric shape constitute respectively our acoustic and articulatory targets.