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Johnson, B. W.

Publications and source records attributed to Johnson, B. W..

2 recordsLinked to original sources

Concurrent MEG-articulography for investigating neuromotor control of speech articulation

Articulography and functional neuroimaging are two major tools for studying the neurobiology of speech production. Until now, however, it has generally not been possible to use both in the same experimental setup because of technical incompatibilities between the two methodologies. Here we describe results from a novel articulography system dubbed Magneto-articulography for the Assessment of Speech Kinematics (MASK), used for the first time to obtain kinematic profiles of oro-facial movements during speech together with concurrent magnetoencephalographic (MEG) measurements of neuromotor brain activity. MASK was used to characterise speech kinematics in a healthy adult, and the results were compared to measurements from the same participant with a conventional electromagnetic articulography (EMA) setup. We also characterised speech movement kinematics with MASK in a group of ten typically developing children, aged 8-12 years. Analyses targeted the gestural landmarks of the utterances /ida/, /ila/ and reiterated productions of /pataka/. These results demonstrate that the MASK technique can be used to reliably characterise movement profiles and kinematic parameters that reflect development of speech motor control, together with MEG measurements of brain responses from speech sensorimotor cortex. This new capability sets the stage for cross-disciplinary efforts to understand the developmental neurobiology of human speech production.

neuroscience

Lateralised cerebral processing of abstract linguistic structure in clear and degraded speech

Providing a plausible neural substrate of speech processing and language comprehension, cortical activity has been shown to track different levels of linguistic structure in connected speech (syllables, phrases and sentences), independent of the physical regularities of the acoustic stimulus. In the current study, we investigated the effect of speech intelligibility on this brain activity as well as the underlying neural sources. Using magnetoencephalography (MEG), brain responses to natural speech and noise-vocoded (spectrally-degraded) speech in nineteen normal hearing participants were measured. Results showed that cortical MEG coherence to linguistic structure changed parametrically with the intelligibility of the speech signal. Cortical responses coherent with phrase and sentence structures were lefthemisphere lateralized, whereas responses coherent to syllable/word structure were bilateral. The enhancement of coherence to intelligible compared to unintelligible speech was also left lateralized and localized to the parasylvian cortex. These results demonstrate that cortical responses to higher level linguistics structures (phrase and sentence level) are sensitive to speech intelligibility. Since the noise-vocoded sentences simulate the auditory input provided by a cochlear implant, such objective neurophysiological measures have potential clinical utility for assessment of cochlear implant performance.

neuroscience