Beta rhythm modulation by speech sounds: somatotopic mapping in somatosensory cortex

Abstract

During speech listening motor regions are somatotopically activated, resembling the activity that subtends actual speech production, suggesting that motor commands can be retrieved from sensory inputs. Crucially, the efficient motor control of the articulators relies on the accurate anticipation of the somatosensory reafference. Nevertheless, evidence about somatosensory activities elicited by auditory speech processing is sparse. The present work looked for specific interactions between auditory speech presentation and somatosensory cortical information processing. We used an auditory speech identification task with sounds having different place of articulation (bilabials and dentals). We tested whether coupling the auditory task with a peripheral electrical stimulation of the lips would affect the pattern of sensorimotor electroencephalographic rhythms. Peripheral electrical stimulation elicits a series of spectral perturbations of which the beta rebound reflects the return-to-baseline stage of somatosensory processing. We show a left-lateralized and selective reduction in the beta rebound following lip somatosensory stimulation when listening to speech sounds produced with the lips (i.e. bilabials). Thus, the somatosensory processing could not return to baseline due to the recruitment of the same neural resources by speech stimuli. Our results are a clear demonstration that heard speech sounds are somatotopically mapped onto somatosensory cortices, according to place of articulation.

The neural oscillatory markers of phonetic convergence during verbal interaction

“…However, using electrocorticography (ECoG) it was shown that beta event-related desynchronization (ERD) is more focused and somatotopically specific than alpha ERD (Crone et al, 1998). More specifically and in line with our findings, somatotopic beta attenuation has also been shown for speech listening (Jenson et al, 2014;Bartoli et al, 2016). More specifically and in line with our findings, somatotopic beta attenuation has also been shown for speech listening (Jenson et al, 2014;Bartoli et al, 2016).…”

“…The speaker role would elicit greater suppression in the alpha range, as often reported in behavioral synchronization tasks (Tognoli & Kelso, ). By contrast, the listener role would produce beta desynchronization, which has been associated to sensorimotor transformations during speech listening tasks (Bartoli, Maffongelli, Campus, & D'Ausilio, ) and top‐down predictive coding of upcoming sensory signals (Cope et al, ).…”

Brain-to-brain entrainment: EEG interbrain synchronization while speaking and listening

“…On the other hand, oscillatory modulations in beta frequencies are supposed to reflect the close relationship between language comprehension and motor functions 36 . It has been shown that the beta rhythm modulation by speech sounds elicits a pattern in the somatosensory cortices of the listener that resembles the activity that subtends actual speech production in the speaker 37 . Furthermore, oscillations in the beta (and theta) band are instrumental in predicting the occurrence of auditory targets 38 .…”

Is the Sensorimotor Cortex Relevant for Speech Perception and Understanding? An Integrative Review

“…As the motor and the somatosensory cortex have parallel somatotopies and with every articulator movement (performed under undeprived conditions) there is specific stimulation of the corresponding somatosensory cortex as well, this position predicts not only specific motor cortex activation in speech perception, but, in addition, somatosensory cortex activation. Indeed, there is evidence for a role of somatosensory systems both in speech production (Tremblay et al, 2003 ; Bouchard et al, 2013 ) and perception (Möttönen et al, 2005 ; Skipper et al, 2007 ; Ito et al, 2009 ; Nasir and Ostry, 2009 ; Correia et al, 2015 ; Bartoli et al, 2016 ). The motor and somatosensory system may already be important for speech perception early in life, since pacifiers blocking specific articulator movements were shown to affect the discrimination of speech sounds even in the first year (Yeung and Werker, 2013 ; for review see Guellaï et al, 2014 ).…”