The phonological loop: is speech special?

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RESEARCH ARTICLE

The phonological loop: is speech special? Isabelle Deschamps1,2 · Melody Courson1,2 · Anthony Steven Dick3 · Pascale Tremblay1,2  Received: 22 February 2020 / Accepted: 16 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract It has been proposed that the maintenance of phonological information in verbal working memory (vWM) is carried by a domain-specific short-term storage center—the phonological loop—which is composed of a phonological store and an articulatory rehearsal system. Several brain regions including the left posterior inferior frontal gyrus (pIFG) and anterior supramarginal gyri (aSMG) are thought to support these processes. However, recent behavioral evidence suggests that verbal and non-verbal auditory information may be processed as part of a unique domain general short-term storage center instead of through specialized subsystems such as the phonological loop. In the current study, we used a single-pulse transcranial magnetic stimulation (TMS)-delayed priming paradigm with speech (syllables) and acoustically complex non-speech sounds (bird songs) to examine whether the pIFG and aSMG are involved in the processing of verbal information or, alternatively, in the processing of any complex auditory information. Our results demonstrate that TMS delivered to both regions had an effect on performance for speech and non-speech stimuli, but the nature of the effect was different. That is, priming was reduced for the speech sounds because TMS facilitated the detection of different but not identical stimuli, and accuracy was decreased for non-speech sounds. Since TMS interfered with both speech and non-speech sounds, these findings support the existence of an auditory short-term storage center located within the dorsal auditory stream. Keywords  Transcranial magnetic stimulation · Auditory working memory · Speech perception · Auditory discrimination · Inferior frontal gyrus · Supramarginal gyrus

Introduction The process of spoken language comprehension is complex, involving perceptual, linguistic as well as cognitive and executive functions such as working memory (WM) and attention. According to most models of speech perception/recognition, to allow for meaning to be extracted from the auditory stream, the auditory speech signal must be Communicated by Melvyn A. Goodale. Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s0022​1-020-05886​-9) contains supplementary material, which is available to authorized users. * Pascale Tremblay [email protected] 1



Département de Réadaptation, Faculté de Médecine, Université Laval, 1050 Avenue de La Médecine, Office 4109, Quebec City, QC G1V 0A6, Canada

2



CERVO Brain Research Centre, Quebec City, QC, Canada

3

Florida International University, Miami, FL, USA



processed acoustically and decomposed into phonological units (Gaskell and Marslen-Wilson 1997, 2002; McClelland and Elman 1986; Norris 1994; Stevens 1972). These phonological units are maintained in