The neuroanatomy of speech sequencing at the syllable level.

Feng Rong,Erica Sun,A Lisette Isenberg,Gregory Hickok,Claude Alain

doi:10.1371/journal.pone.0196381

Feng Rong, Erica Sun + Show 3 more

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https://doi.org/10.1371/journal.pone.0196381

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Journal: PloS one	Publication Date: Oct 9, 2018
Citations: 28	License type: CC BY 4.0

Affiliation: University of California, Irvine

Abstract

Correctly ordering a sequence of speech sounds is a crucial aspect of speech production. Although studies have yielded a rich body of data on the neural substrates of visuomotor sequencing and sequence learning, research on brain regions and their functions involving speech sequence production hasn’t attracted much attention until recently. Previous functional MRI studies manipulating the complexity of sequences at the phonemic, syllabic, and suprasyllabic levels have revealed a network of motor-related cortical and sub-cortical speech regions. In this study, we directly compared human brain activity measured with functional MRI during processing of a sequence of syllables compared with the same syllables processed individually. Among a network of regions independently identified as being part of the sensorimotor circuits for speech production, only the left posterior inferior frontal gyrus (pars opercularis, lIFG), the supplementary motor area (SMA), and the left inferior parietal lobe (lIPL) responded more during the production of syllable sequences compared to producing the same syllables articulated one at a time.

Highlights

Fluent speech requires the rapid coordination of vocal tract gestures to produce the intended sequence of phonemes, syllables, and words
We note that the localizer task includes the sequence (RS) condition used in the main experiment. This is by design as we aimed to identify the speech network with the most difficult condition and independently determine which of the regions of interest (ROIs) were modulated by the sequence versus non-sequence manipulation
A much smaller set of studies have suggested that only a subset of this production network, frontal lobe motor regions, is involved in sequencing, while other studies have questioned even this conclusion

Summary

Introduction

Fluent speech requires the rapid coordination of vocal tract gestures to produce the intended sequence of phonemes (segments), syllables, and words. A number of studies have investigated the neural foundation of speech production using a range of methods with notable progress in mapping the broad stages of speech (e.g., lexicalsemantic versus phonological) onto neural networks [12,13,14,15,16,17]. Another line of research has made significant progress in understanding the role of sensorimotor circuits in speech motor control [10, 18,19,20,21,22,23,24]. Overall these studies have identified a distributed speech production network that includes pre- and post-central gyri, medial premotor cortex (SMA/pre-SMA), lateral premotor cortex, posterior inferior frontal gyrus, anterior insula, superior temporal gyrus, and the posterior planum temporale region, termed Spt [25, 26], as well as portions of the cerebellum and basal ganglia [24]

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