Effect of Bilateral Opercular Syndrome on Speech Perception.

Grant M Walker,Patrick Sarahan Rollo,Nitin Tandon,Gregory Hickok

doi:10.1162/nol_a_00037

Grant M Walker, Patrick Sarahan Rollo + Show 2 more

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https://doi.org/10.1162/nol_a_00037

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Abstract

Speech perception ability and structural neuroimaging were investigated in two cases of bilateral opercular syndrome. Due to bilateral ablation of the motor control center for the lower face and surrounds, these rare cases provide an opportunity to evaluate the necessity of cortical motor representations for speech perception, a cornerstone of some neurocomputational theories of language processing. Speech perception, including audiovisual integration (i.e., the McGurk effect), was mostly unaffected in these cases, although verbal short-term memory impairment hindered performance on several tasks that are traditionally used to evaluate speech perception. The results suggest that the role of the cortical motor system in speech perception is context-dependent and supplementary, not inherent or necessary.

Highlights

Despite centuries of discussion and debate, the role of the motor system in speech perception continues to inspire curiosity and empirical investigations
The results suggest that the role of the cortical motor system in speech perception is context-dependent and supplementary, not inherent or necessary
Researchers generally agree that a strong version of the motor theory—that motor speech systems are necessary for speech perception—is untenable

Summary

Introduction

Despite centuries of discussion and debate, the role of the motor system in speech perception continues to inspire curiosity and empirical investigations. The discovery of mirror neurons has renewed interest in motor theories of speech perception These theories posit that motoric gesture representations play either a primary or supportive role in perceiving speech sounds via articulatory recoding (motoric simulation), thereby assisting the resolution of the indeterminacy problem in mapping from acoustic to phonological perception. Consistent with this theory, functional imaging research has shown conclusively that frontal motor speechrelated areas activate during speech listening (Hickok et al, 2003; Watkins & Paus, 2004; Wilson et al, 2004) and transcranial magnetic stimulation (TMS) of premotor and primary motor areas can modulate performance on some perception tasks in an effector-specific manner (D’Ausilio et al, 2009; Möttönen & Watkins, 2012; Pulvermüller & Fadiga, 2010).

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