Two Tongues, One Brain: Imaging Bilingual Speech Production

This review considers speaking in a second language from the perspective of motor–sensory control. Previous studies relating brain function to the prior acquisition of two or more languages (neurobilingualism) have investigated the differential demands made on linguistic representations and processes, and the role of domain-general cognitive control systems when speakers switch between languages. In contrast to the detailed discussions on these higher functions, typically articulation is considered only as an underspecified stage of simple motor output. The present review considers speaking in a second language in terms of the accompanying foreign accent, which places demands on the integration of motor and sensory discharges not encountered when articulating in the most fluent language. We consider why there has been so little emphasis on this aspect of bilingualism to date, before turning to the motor and sensory complexities involved in learning to speak a second language as an adult. This must involve retuning the neural circuits involved in the motor control of articulation, to enable rapid unfamiliar sequences of movements to be performed with the goal of approximating, as closely as possible, the speech of a native speaker. Accompanying changes in motor networks is experience-dependent plasticity in auditory and somatosensory cortices to integrate auditory memories of the target sounds, copies of feedforward commands from premotor and primary motor cortex and post-articulatory auditory and somatosensory feedback. Finally, we consider the implications of taking a motor–sensory perspective on speaking a second language, both pedagogical regarding non-native learners and clinical regarding speakers with neurological conditions such as dysarthria

A theory of second language acquisition within the framework of natural phonology: a Polish \u2013 English contrastive study

[i]Keywords: acquisition of a second language; Natural Phonology; comparative linguistics; Polish \u2013 English contrastive grammar; second language learning/teaching[/i] S\u142owa kluczowe: akwizycja drugiego j\u119zyka; Fonologia Naturalna; j\u119zykoznawstwo por\uf3wnawcze; gramatyka kontrastywna j\u119zyka polskiego i angielskiego; nabywanie/nauczanie drugiego j\u119zyk

Towards speech recognition using palato-lingual contact patterns for voice restoration.

The loss of speech following a laryngectomy presents substantial challenges, and a number of devices have been developed to assist these patients. These devices range from the electrolarynx to tracheoesophageal speech. However, all of these devices and techniques have concentrated on producing sound from the patient’s vocal tract. Research into a new type of artificial larynx is presented. This new device utilizes the measurement of dynamic tongue-palate contact patterns to infer intended speech. The dynamic tongue measurement is achieved with the use of an existing palatome- ter and pseudopalate. These signals are then converted to 2-D Space-Time plots and feature extraction methods (such as Principal Component Analysis, Fourier Descrip- tors and Generic Fourier Descriptors) are used to extract suitable features for use as input to neural network systems. Two types of neural network (Multi-layer Percep- trons and Support Vector Machines) are investigated and a voting system is formed. The final system can correctly identify fifty common English words 94.14% of the time with a rejection rate of 17.74%. Voice morphing is investigated as a technique to match the artificially synthesized voice to the laryngectomy patient’s original voice. It is successfully implemented thus creating a transfer function that can change one person’s voice to sound like another’s. Once the voting system has correctly identified the word said by the patient the word is then synthesized in the patient’s pre-laryngectomy voice. The final artificial larynx system solves a number of the problems inherent in previ- ous artificial larynx designs (such as poor voice quality and invasiveness). This new artificial larynx uses current technology in a new way to produce a viable solution for alaryngeal patients

Investigating the motor-sensory learning of foreign speech

This thesis presents an investigation of bilingualism as a motor learning skill, with success ultimately measured in terms of strength of a foreign accent, in contrast to the many studies of bilingualism in terms of linguistic competence. My research used functional magnetic resonance (fMRI) imaging to investigate feedforward (motor) and feedback (auditory and somatosensory) systems involved in the production of foreign speech and how these systems are modulated by proficiency levels. I investigated the function of the frontal operculum and the temporo-parietal junction (TPJ) – planum temporale (posterior auditory association cortex) and parietal operculum (somatosensory association cortex) – during speech. The frontal operculum, strongly lateralised to the left, has been associated with speech since Broca performed his classic post mortem lesion-deficit analysis. Interest in the TPJ has arisen because of recent publications proposing the posterior half of the left planum temporale (± adjacent parietal operculum) as a ‘sensorimotor interface’ for speech production. My research compared activity within the frontal operculum and the TPJ during overt and covert speech. A second fMRI study examined retrospective proficiency based on existing language skills in people with English as a foreign language who were scanned during speech production in their native language and in English. A third fMRI study manipulated proficiency by training monolingual native English participants in the production of foreign speech sounds, with scanning pre- and post-training. This allowed measures of changes in activity (indicating rapid plasticity) following a short period of behavioural training in articulating novel foreign speech sounds. Training effects were observed predominantly in the striatum, and further analyses indicated that striatal activity in vocal learning is modulated by proficiency