The Motor System's [Modest] Contribution to Speech Perception

Abstract

<p>Recent evidence suggests that the motor system may have a facilitatory role in speech perception during noisy listening conditions. Studies clearly show an association between activity in auditory and motor speech systems, but also hint at a causal role for the motor system in noisy speech perception. However, in the most compelling "causal" studies performance was only measured at a single signal-to-noise ratio (SNR). If listening conditions must be noisy to invoke causal motor involvement, then effects will be contingent on the SNR at which they are tested. We used articulatory suppression to disrupt motor-speech areas while measuring phonemic identification across a range of SNRs. As controls, we also measured phoneme identification during passive listening, mandible gesturing, and foot-tapping conditions. Two-parameter (threshold, slope) psychometric functions were fit to the data in each condition. Our findings indicate: (1) no effect of experimental task on psychometric function slopes; (2) a small effect of articulatory suppression, in particular, on psychometric function thresholds. The size of the latter effect was 1 dB (~5% correct) on average, suggesting, at best, a minor modulatory role of the speech motor system in perception.</p>

A Review on Treatment-Related Brain Changes in Aphasia

“…In addition, in the same survey, only 50% of respondents agreed on the precise location of Broca's region in the triangular and opercular part of the left inferior frontal gyrus (IFG; Tremblay & Dick, 2016). Furthermore, the strict functional division between language production in Broca's region and language comprehension in Wernicke's region is not valid because many fMRI studies have demonstrated that both language modalities share neural resources (Menenti, Gierhan, Segaert, & Hagoort, 2011;Segaert, Menenti, Weber, Petersson, & Hagoort, 2012;Stokes, Venezia, & Hickok, 2019).…”

Rapid Cortical Plasticity Induced by Active Associative Learning of Novel Words in Human Adults

“…These routes are thought to participate in acoustic/phonological transcoding (Catani et al, 2005). The recurrent motor-perceptual interaction is known to facilitate speech perception of unfamiliar speech stimuli, e.g., distorted speech and novel or low-frequency words (Wu et al, 2014;Stokes et al, 2019). Therefore, greater involvement of the entire perisylvian network into the APW compared to the NPW response in our experiment may indicate that newly learned semantic association boosted perceptual processing of incoming novel linguistic stimuli.…”

Cortical Networks for Recognition of Speech with Simultaneous Talkers

“…A prominent challenge to the classic view is the motor theory of speech perception, which posits that gesturesnot speech soundsare the objects of speech perception, thus implicating motor brain regions in receptive speech (Liberman, 1957;Liberman and Mattingly, 1985;Galantucci et al, 2006). Although the motor theory of speech perception was initially rebuked due to its failure to account for the classic neuropsychological findings, among other shortcomings (Diehl et al, 2004;Holt and Lotto, 2008;Lotto et al, 2009;Scott et al, 2009;Venezia and Hickok, 2009;Stokes et al, 2019), it experienced a major resurgence when modern, non-invasive brain imaging methods revealed unequivocally that inferior frontal brain regions are engaged during speech perception (Rizzolatti and Craighero, 2004;Pulvermuller and Fadiga, 2010;D'Ausilio et al, 2012). More recently, even sensory-oriented speech researchers have come to acknowledge that frontal motor regions play at least some role in speech perception, leading to a moderation of the classic model in which bottom-up sensory processing is subserved by superior temporal brain regions while inferior frontal regions contribute to top-down or task-sensitive aspects of speech perception (Binder et al, 2004;Hickok and Poeppel, 2007;Venezia et al, 2012).…”

“…Frontal brain circuits may be especially important for recognition of degraded speech or speech in background noise. Indeed, this notion has been embraced by motor theorists, with recent variants of the motor theory suggesting that top-down motor predictions figure most prominently in speech perception when the input signal is corrupted or otherwise ambiguous (Stokes et al, 2019), and by the nascent field of cognitive hearing science, which posits a significant role for domain general or cognitive systems when speech is either intrinsically (e.g., with hearing loss) or extrinsically (e.g., with background noise) distorted (Arlinger et al, 2009;Rönnberg et al, 2011;Pichora-Fuller et al, 2016). Notably, while these perspectives differ in terms of their emphasis on frontal-motor versus frontal-cognitive mechanisms, they fundamentally agree that frontal contributions scale with the demands of the task and thus do not constitute a core component of bottom-up speech perception.…”