The rapid release of prepared movements by a loud acoustic stimulus capable of eliciting a startle response has been termed the StartReact effect (Valls-Solé et al., 1999), and premotor reaction times (PMTs) of <70 ms are often observed. Two explanations have been given for these short latency responses. The subcortical storage and triggering hypothesis suggests movements that can be prepared in advance of a “go” signal are stored and triggered from subcortical areas by a startling acoustic stimulus (SAS) without cortical involvement. Alternatively, it has been hypothesized that the SAS can trigger movements from cortical areas through a faster pathway ascending from subcortical structures. Two experiments were designed to examine the possible role of primary motor cortex in the StartReact effect. In Experiment 1, we used suprathreshold transcranial magnetic stimulation (TMS) during the reaction time (RT) interval to induce a cortical silent period in the contralateral primary motor cortex (M1). Thirteen participants performed 20° wrist extension movements as fast as possible in response to either a control stimulus (82dB) or SAS (124 dB). PMTs for startle trials were faster than control trials, while TMS significantly delayed movement onset compared to No TMS or Sham TMS conditions. In Experiment 2, we examined the StartReact effect in a highly cortically represented action involving speech of a consonant-vowel (CV) syllable. Similar to previous work examining limb movements, a robust StartReact effect was found. Collectively, these experiments provide evidence for cortical (M1) involvement in the StartReact effect.

A finite element method (FEM) based numerical model of upper airway structures (jaw, tongue, maxilla, soft palate) was implemented to observe interactions between the soft palate and tongue, and in particular to distinguish the contributions of individual muscles in producing speech-relevant constrictions of the oropharyngeal isthmus (OPI), or “uvular” region of the oral tract. Simulations revealed a sphincter-like general operation for the OPI, particularly with regard to the function of the palatoglossus muscle. Further, as has been observed with the lips, the OPI can be controlled by multiple distinct muscular mechanisms, each reliably producing a different sized opening and robust to activation noise, suggestive of a modular view of speech motor control. As off-midline structures of the OPI are difficult to observe during speech production, biomechanical simulation offers a promising approach to studying these structures.

In Taiwan Mandarin, retroflex [ʂ] is allegedly merging with dental [s], reducing the traditional three-way contrast between sibilant fricatives (i.e., dental [s]–retroflex [ʂ]–alveopalatal [ɕ]) to a two-way contrast. Most of the literature on the observed merging focuses on the acoustic properties and perceptual identification of the sibilants, whereas much less attention has been drawn to the articulatory evidence accounting for the aforementioned sibilant merging. The current study employed ultrasound imaging techniques to uncover the tongue postures for the three sibilant fricatives [s, ʂ, ɕ] in Taiwan Mandarin occurring before vowels [a], [ɨ], and [o]. Results revealed varying classes of the [s–ʂ] merger: complete merging ( overlap), no merging ( non-overlap), and context-dependent merging ( context-dependent overlap, which only occurred before [a]). The observed [s–ʂ] merger was also confirmed by the perceptual identification by trained phoneticians. Center of gravity (CoG), a reliable spectral moment of identifying different sibilant fricatives, was also measured to reflect the articulatory–acoustic correspondence. Results showed that the [s–ʂ] merger varies across speakers and may also be conditioned by vowel contexts and that articulatory mergers may not be entirely reflected in CoG values, suggesting that auxiliary articulatory gestures may be employed to maintain the acoustic contrast.

This study explores the phenomenon of uvularization in the vowel systems of two Heishui County varieties of Qiang, a Sino-Tibetan language of Sichuan Province, China. Ultrasound imaging (one speaker) shows that uvularized vowels have two tongue gestures: a rearward gesture, followed by movement toward the place of articulation of the corresponding plain vowel. Time-aligned acoustic and articulatory data show how movement toward the uvula correlates with changes in the acoustic signal. Acoustic correlates of uvularization (taken from two speakers) are seen most consistently in raising of vowel F1, lowering of F2 and in raising of the difference F3-F2. Imaging data and the formant structure of [l] show that uvular approximation can begin during the initial consonant that precedes a uvularized vowel. Uvularization is reflected phonologically in the phonotactic properties of vowels, while vowel harmony aids in the identification of plain–uvularized vowel pairs. The data reported in this paper argue in favor of a revision of the catalog of secondary articulations recognized by the International Phonetic Alphabet, in order to include uvularization, which can be marked with the symbol [ʶ] in the case of approximation and [χ] for secondary uvular frication.