No evidence of somatotopic place of articulation feature mapping in motor cortex during passive speech perception

Abstract

The motor theory of speech perception has experienced a recent revival due to a number of studies implicating the motor system during speech perception. In a key study, Pulvermüller et al. (2006) showed that premotor/motor cortex differentially responds to the passive auditory perception of lip and tongue speech sounds. However, no study has yet attempted to replicate this important finding from nearly a decade ago. The objective of the current study was to replicate the principal finding of Pulvermüller et al. (2006) and generalize it to a larger set of speech tokens while applying a more powerful statistical approach using multivariate pattern analysis (MVPA). Participants performed an articulatory localizer as well as a speech perception task where they passively listened to a set of eight syllables while undergoing fMRI. Both univariate and multivariate analyses failed to find evidence for somatotopic coding in motor or premotor cortex during speech perception. Positive evidence for the null hypothesis was further confirmed by Bayesian analyses. Results consistently show that while the lip and tongue areas of the motor cortex are sensitive to movements of the articulators, they do not appear to preferentially respond to labial and alveolar speech sounds during passive speech perception.

Transformation of speech sequences in human sensorimotor circuits

“…An alternative hypothesis is that, when we silently rehearse a series of words, we employ representations that are distinct from those involved in the original auditory perception. Contrasting with early observations of shared representations (13), recent intracranial and imaging studies have found that ventral sensorimotor circuits respond with distinct activity patterns during the perception and production of the same syllables (e.g., "ba") (14,15). Moreover, widespread bilateral cortical circuits appear to "transform" between sensory and motor representations when pseudowords (e.g., "pob") are held in mind and spoken aloud (16).…”

The motor system’s [modest] contribution to speech perception

“…Barnaud et al, 2018;Skipper, Devlin, & Lametti, 2017), but the bulk of the experimental data on cortical motor involvement in speech perception remains correlational (Hickok, 2010;Venezia & Hickok, 2009). A possible direction forward is motivated by two recent neuroimaging and direct cortical recording studies, which converge to suggest that cortical motor representations of heard speech are organized in terms of auditory rather than articulatory features (Arsenault & Buchsbaum, 2016;Cheung, Hamilton, Johnson, & Chang, 2016). This "auditory mode" of processing in the speech motor cortex merits further investigation.…”

Transformation of Speech Sequences in Human Sensorimotor Circuits

“…representations that are distinct from those involved in the original auditory perception. In 23 distinction with early observations of shared representations (Pulvermüller et al, 2006), recent 24 intracranial and imaging studies have found that ventral sensorimotor circuits respond with 25 distinct activity patterns during the perception and production of the same syllables (e.g., "ba", 1 Cheung et al, 2016; Arsenault and Buchsbaum, 2016). Moreover, widespread bilateral cortical 2 circuits appear to "transform" between sensory and motor representations when pseudowords 3 (e.g., "pob") are held in mind and spoken aloud (Cogan et al, 2014).…”