Abstract
While much progress has been made in how brain organization supports language function, the language network's ability to adapt to immediate disturbances by means of reorganization remains unclear. The aim of this study was to examine acute reorganizational changes in brain activity related to conceptual and lexical retrieval in unimpaired language production following transient disruption of the left middle temporal gyrus (MTG). In a randomized single‐blind within‐subject experiment, we recorded the electroencephalogram from 16 healthy participants during a context‐driven picture‐naming task. Prior to the task, the left MTG was perturbed with real continuous theta‐burst stimulation (cTBS) or sham stimulation. During the task, participants read lead‐in sentences creating a constraining (e.g., “The farmer milks the”) or nonconstraining context (e.g., “The farmer buys the”). The last word was shown as a picture that participants had to name (e.g., “cow”). Replicating behavioral studies, participants were overall faster in naming pictures following a constraining relative to a nonconstraining context, but this effect did not differ between real and sham cTBS. In contrast, real cTBS increased overall error rates compared to sham cTBS. In line with previous studies, we observed a decrease in alpha‐beta (8–24 Hz) oscillatory power for constraining relative to nonconstraining contexts over left temporal–parietal cortex after participants received sham cTBS. However, following real cTBS, this decrease extended toward left prefrontal regions associated with both domain‐general and domain‐specific control mechanisms. Our findings provide evidence that immediately after perturbing the left MTG, the lexical‐semantic network is able to quickly reconfigure, also recruiting domain‐general regions.
Highlights
In the past decades, much progress has been made in understanding how the brain is organized to support language functioning (Hickok & Poeppel, 2007; Jackson, Bajada, Rice, Cloutman, & Lambon Ralph, 2018; Poeppel, 2014; Price, 2010; Price, 2012; Tzourio-Mazoyer, Perrone-Bertolotti, Jobard, Mazoyer, & Baciu, 2017)
Lesions in language-relevant regions trigger an upregulation of intact, domain-general networks, within the so-called Multiple Demand Network (MDN)
The majority of the empirical work regarding cortical reorganization following transient perturbation or real lesions has been conducted using functional magnetic resonance imaging, which provides an indirect measure of neuronal activity (Logothetis & Wandell, 2004) on a rough temporal scale in the order of seconds. It remains largely unknown whether the activity observed outside of the left-hemisphere language network is concurrent with task-related, language-network activity or whether it emerges after the language system has failed
Summary
Much progress has been made in understanding how the brain is organized to support language functioning (Hickok & Poeppel, 2007; Jackson, Bajada, Rice, Cloutman, & Lambon Ralph, 2018; Poeppel, 2014; Price, 2010; Price, 2012; Tzourio-Mazoyer, Perrone-Bertolotti, Jobard, Mazoyer, & Baciu, 2017). The majority of the empirical work regarding cortical reorganization following transient perturbation or real lesions has been conducted using functional magnetic resonance imaging, which provides an indirect (i.e., metabolic) measure of neuronal activity (Logothetis & Wandell, 2004) on a rough temporal scale in the order of seconds (but see Cipollari et al, 2015; Dammekens, Vanneste, Ost, & De Ridder, 2014; Sarasso et al, 2014 for work combining electrophysiological and neuromodulatory techniques in aphasia, and Tang et al, 2018; Woźniak-Kwasniewska, Szekely, Aussedat, Bougerol, & David, 2014 for evidence of the effect of cTBS on electrophysiological responses) As such, it remains largely unknown whether the activity observed outside of the left-hemisphere language network is concurrent with task-related, language-network activity or whether it emerges after the language system has failed. Response to the acute focal perturbation, indicating that acute cortical adaptation is confined to the lesioned hemisphere, where disturbance to function is compensated by other network nodes (Hartwigsen, 2018)
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