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

Abstract

In the neuroscience of language, phonemes are frequently described as multimodal units whose neuronal representations are distributed across perisylvian cortical regions, including auditory and sensorimotor areas. A different position views phonemes primarily as acoustic entities with posterior temporal localization, which are functionally independent from frontoparietal articulatory programs. To address this current controversy, we here discuss experimental results from functional magnetic resonance imaging (fMRI) as well as transcranial magnetic stimulation (TMS) studies. On first glance, a mixed picture emerges, with earlier research documenting neurofunctional distinctions between phonemes in both temporal and frontoparietal sensorimotor systems, but some recent work seemingly failing to replicate the latter. Detailed analysis of methodological differences between studies reveals that the way experiments are set up explains whether sensorimotor cortex maps phonological information during speech perception or not. In particular, acoustic noise during the experiment and ‘motor noise’ caused by button press tasks work against the frontoparietal manifestation of phonemes. We highlight recent studies using sparse imaging and passive speech perception tasks along with multivariate pattern analysis (MVPA) and especially representational similarity analysis (RSA), which succeeded in separating acoustic-phonological from general-acoustic processes and in mapping specific phonological information on temporal and frontoparietal regions. The question about a causal role of sensorimotor cortex on speech perception and understanding is addressed by reviewing recent TMS studies. We conclude that frontoparietal cortices, including ventral motor and somatosensory areas, reflect phonological information during speech perception and exert a causal influence on language understanding.

Semantically defined subdomains of functional neuroimaging literature and their corresponding brain regions

“…The activation map of Cluster 1 ( knowledge representation and language processing ; Figure a) is similar to other published meta‐analytic maps and reviews of language processing and semantic representation (Binder, Desai, Graves, & Conant, ; Bookheimer, ; Fedorenko & Thompson‐Schill, ; Price, ). The activation map of Cluster 3 ( Sensation, Movement and Action ; Figure c) is similar to other maps from studies investigating pain localization (Amanzio, Benedetti, Porro, Palermo, & Cauda, ; Friebel, Eickhoff, & Lotze, ; Perini, Bergstrand, & Morrison, ; Schomers & Pulvermüller, ; Vierck, Whitsel, Favorov, Brown, & Tommerdahl, ) in addition to the somatosensory co‐activation network (Smith et al, ). Finally, the activation map of Cluster 5 ( decision, emotion, and substance use ; Figure e) is also highly similar to the map of the structures involved in different aspects of emotional processing and decision‐making (Bartra, McGuire, & Kable, ; Buhle et al, ; Etkin & Wager, ; Lindquist, ; Phan, Wager, Taylor, & Liberzon, ).…”

Singing training predicts increased insula connectivity with speech and respiratory sensorimotor areas at rest

“…Vocalization related movements are accompanied by proprioceptive, kinesthetic, and interoceptive consequences, which in turn are integrated with the motor system to guide song and speech production (Bernardi et al, 2015;Gozaine and Clark, 2005;Nasir and Ostry, 2006;Simonyan and Horwitz, 2011;Smotherman, 2007;Tremblay et al, 2003;Wyke, 1974). For example, every movement specifically stimulates a corresponding somatosensory region in S1 (Giraud and Poeppel, 2012;Schomers and Pulvermuller, 2016), which is intrinsically connected to ipsilateral M1 and IPL (Borich et al, 2015;Bouchard et al, 2013), involves the thalamus (Ackermann and Riecker, 2010;Hwang et al, 2017), and becomes tightly associated with corresponding auditory-motor transformations (Ito et al, 2016;Ito andOstry, 2010, 2012;Ito et al, 2015;Ito et al, 2009). Moreover, M1 sends its strongest subcortical projections to the putamen (Simonyan and Horwitz, 2011), which shows increased activations in more proficient singers (Kleber et al, 2010;Segado et al, 2018;Zarate and Zatorre, 2008).…”

Atypical MEG inter-subject correlation during listening to continuous natural speech in dyslexia

“…In addition, other linguistically relevant and extralinguistic areas showed ISC during listening to speech. Of those, inferior frontal postcentral and parietal areas, specifically premotor areas, belong to a network involved in auditory and speech perception (Giraud and Poeppel, 2012;Schomers & Pulvermüller, 2016;Lima et al, 2016). Moreover, precuneus has been shown to play a role in higher-level social processes, such as role or perspective taking and episodic memory retrieval (Cavanna & Trimble, 2006), and it was suggested to be part of the theory-of-mind network together with STS and temporal-pole areas (Mar, 2011).…”