Die vergessene Hemisphäre: rechtshemisphärische Beiträge zu modalitäts-unabhängigen phonologischen Aspekten der Sprachverarbeitung im gesunden menschlichen Gehirn

This thesis investigates the representation of phonological language aspects in the healthy human brain, especially the contribution of the right hemisphere. Using functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS), it is demonstrated that the left and right supramarginal gyri are essential for phonological processing. It is also shown that the left as well as the right posterior inferior frontal gyri contribute to efficient phonological decisions. Finally, an fMRI study reveals a frontal network for phonological aspects of language production. These results demonstrate a contribution of both hemispheres to efficient phonological aspects of language comprehension as well as production. Together, these results question the notion of a left-dominant network of brain regions for language processing.In dieser Arbeit wurde die Repräsentation phonologischer Sprachaspekte im gesunden Gehirn untersucht. Von besonderem Interesse war der Beitrag der rechten Hemisphäre. Dabei wurde mit funktioneller Magnetresonanztomographie (fMRT) und transkranieller Magnetstimulation die Relevanz des linken und rechten Gyrus supramarginalis für phonologische Sprachaspekte nachgewiesen. Weiterhin wurde gezeigt, dass der linke und rechte posteriore Gyrus frontalis inferior ebenfalls essentiell für die phonologische Verarbeitung sind. Abschließend wurde mittels fMRT ein frontales Netzwerk identifiziert, das an phonologischen Aspekten der Sprachproduktion beteiligt ist. Insgesamt zeigen die vorliegenden Ergebnisse, dass Areale beider Hemisphären gleichermaßen relevant für effiziente phonologische Entscheidungen im gesunden Gehirn sind. Dies stellt die bisher in der Literatur vorherrschende Dominanz der linken Hemisphäre für die Verarbeitung von Sprache in Frage

Efficient high-resolution TMS mapping of the human motor cortex by nonlinear regression

Transcranial magnetic stimulation (TMS) is a powerful tool to investigate causal structure-function relationships in the human brain. However, a precise delineation of the effectively stimulated neuronal populations is notoriously impeded by the widespread and complex distribution of the induced electric field. Here, we propose a method that allows rapid and feasible cortical localization at the individual subject level. The functional relationship between electric field and behavioral effect is quantified by combining experimental data with numerically modeled fields to identify the cortical origin of the modulated effect. Motor evoked potentials (MEPs) from three finger muscles were recorded for a set of random stimulations around the primary motor area. All induced electric fields were nonlinearly regressed against the elicited MEPs to identify their cortical origin. We could distinguish cortical muscle representation with high spatial resolution and localized them primarily on the crowns and rims of the precentral gyrus. A post-hoc analysis revealed exponential convergence of the method with the number of stimulations, yielding a minimum of about 180 random stimulations to obtain stable results. Establishing a functional link between the modulated effect and the underlying mode of action, the induced electric field, is a fundamental step to fully exploit the potential of TMS. In contrast to previous approaches, the presented protocol is particularly easy to implement, fast to apply, and very robust due to the random coil positioning and therefore is suitable for practical and clinical applications

Visual sensory cortices causally contribute to auditory word recognition following sensorimotor-enriched vocabulary training

Funding This work was funded by German Research Foundation (grant KR 3735/3-1), a Max Planck Research Group to K.v.K., and an Erasmus Mundus Postdoctoral Fellowship to B.M.. B.M. is also supported by the European Research Council Consolidator grant SENSOCOM 647051 to K.v.K..Peer reviewedPublisher PD

How can we learn foreign language vocabulary more easily?

The authors would like to thank those who assisted in the translation of the articles in this Collection to make them more accessible to kids outside English-speaking countries, and for the Jacobs Foundation for providing the funds necessary to translate the articles. For this article, they would especially like to thank Nienke van Atteveldt and Sabine Peters for the Dutch translation. This work was funded by the German Research Foundation grant KR 3735/3-1, a Schulbezogene Forschung grant from the Saxony Zentrum für Lehrerbildung und Schulforschung (ZLS), and an Erasmus Mundus Postdoctoral Fellowship in Auditory Cognitive Neuroscience. BM also supported by the European Research Council Consolidator Grant SENSOCOM 647051 to KvK.Peer reviewedPublisher PD

Neuromodulatory effects of transcranial magnetic stimulation on language performance in healthy participants: Systematic review and meta-analysis

BackgroundThe causal relationships between neural substrates and human language have been investigated by transcranial magnetic stimulation (TMS). However, the robustness of TMS neuromodulatory effects is still largely unspecified. This study aims to systematically examine the efficacy of TMS on healthy participants’ language performance.MethodsFor this meta-analysis, we searched PubMed, Web of Science, PsycINFO, Scopus, and Google Scholar from database inception until October 15, 2022 for eligible TMS studies on language comprehension and production in healthy adults published in English. The quality of the included studies was assessed with the Cochrane risk of bias tool. Potential publication biases were assessed by funnel plots and the Egger Test. We conducted overall as well as moderator meta-analyses. Effect sizes were estimated using Hedges’g (g) and entered into a three-level random effects model.ResultsThirty-seven studies (797 participants) with 77 effect sizes were included. The three-level random effects model revealed significant overall TMS effects on language performance in healthy participants (RT: g = 0.16, 95% CI: 0.04–0.29; ACC: g = 0.14, 95% CI: 0.04–0.24). Further moderator analyses indicated that (a) for language tasks, TMS induced significant neuromodulatory effects on semantic and phonological tasks, but didn’t show significance for syntactic tasks; (b) for cortical targets, TMS effects were not significant in left frontal, temporal or parietal regions, but were marginally significant in the inferior frontal gyrus in a finer-scale analysis; (c) for stimulation parameters, stimulation sites extracted from previous studies, rTMS, and intensities calibrated to the individual resting motor threshold are more prone to induce robust TMS effects. As for stimulation frequencies and timing, both high and low frequencies, online and offline stimulation elicited significant effects; (d) for experimental designs, studies adopting sham TMS or no TMS as the control condition and within-subject design obtained more significant effects.DiscussionOverall, the results show that TMS may robustly modulate healthy adults’ language performance and scrutinize the brain-and-language relation in a profound fashion. However, due to limited sample size and constraints in the current meta-analysis approach, analyses at a more comprehensive level were not conducted and results need to be confirmed by future studies.Systematic review registration[https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=366481], identifier [CRD42022366481]

Imaging Neuroscience opening editorial

In this editorial we introduce a new non-profit open access journal, Imaging Neuroscience. In April 2023, editors of the journals NeuroImage and NeuroImage:Reports resigned, and a month later launched Imaging Neuroscience. NeuroImage had long been the leading journal in the field of neuroimaging. While the move to fully open access in 2020 represented a positive step toward modern academic practices, the publication fee was set to a level that the editors found unethical and unsustainable. The publisher of NeuroImage, Elsevier, was unwilling to reduce the fee after much discussion. This led us to launch Imaging Neuroscience with MIT Press, intended to replace NeuroImage as our field’s leading journal, but with greater control by the neuroimaging academic community over publication fees and adoption of modern and ethical publishing practices

A checklist for assessing the methodological quality of concurrent tES-fMRI studies (ContES checklist): a consensus study and statement

Background: Low intensity transcranial electrical stimulation (tES), including alternating or direct current stimulation (tACS or tDCS), applies weak electrical stimulation to modulate the activity of brain circuits. Integration of tES with concurrent functional magnetic resonance imaging (fMRI) allows for the mapping of neural activity during neuromodulation, supporting causal studies of both brain function and tES effects. Methodological aspects of tES-fMRI studies underpin the results, and reporting them in appropriate detail is required for reproducibility and interpretability. Despite the growing number of published reports, there are no consensus-based checklists for disclosing methodological details of concurrent tES-fMRI studies. Objective: To develop a consensus-based checklist of reporting standards for concurrent tES-fMRI studies to support methodological rigor, transparency, and reproducibility (ContES Checklist). Methods: A two-phase Delphi consensus process was conducted by a steering committee (SC) of 13 members and 49 expert panelists (EP) through the International Network of the tES-fMRI (INTF) Consortium. The process began with a circulation of a preliminary checklist of essential items and additional recommendations, developed by the SC based on a systematic review of 57 concurrent tES-fMRI studies. Contributors were then invited to suggest revisions or additions to the initial checklist. After the revision phase, contributors rated the importance of the 17 essential items and 42 additional recommendations in the final checklist. The state of methodological transparency within the 57 reviewed concurrent tES-fMRI studies was then assessed using the checklist. Results: Experts refined the checklist through the revision and rating phases, leading to a checklist with three categories of essential items and additional recommendations: (1) technological factors, (2) safety and noise tests, and (3) methodological factors. The level of reporting of checklist items varied among the 57 concurrent tES-fMRI papers, ranging from 24% to 76%. On average, 53% of checklist items were reported in a given article. Conclusions: Use of the ContES checklist is expected to enhance the methodological reporting quality of future concurrent tES-fMRI studies, and increase methodological transparency and reproducibility

Failure to Improve Verbal Fluency with Transcranial Direct Current Stimulation

Previous studies in healthy populations have provided equivocal evidence whether the application of anodal transcranial direct current stimulation (tDCS) over the left prefrontal cortex (PFC) can improve performance in verbal fluency tasks. In this double-blind, randomised within-participant study, we investigated whether anodal tDCS over the left PFC improves verbal fluency performance relative to sham tDCS. Forty eight healthy native German speakers performed two verbal fluency tasks after having received 20 min of anodal or sham tDCS over the left PFC. During stimulation, participants performed a picture naming task, which was expected to increase neuronal activity in the targeted region. We found no modulation of verbal fluency performance following anodal tDCS, with virtually identical overall scores across tDCS conditions. Furthermore, initiation time (i.e., time to produce the first correct utterance) was not affected by tDCS. As an unexpected finding, picture naming latencies were significantly longer during anodal compared to sham tDCS. Yet, changes in the naming task were not predictive of performance changes in the fluency task. Overall, the current study found no evidence that verbal fluency performance in healthy speakers could be improved by excitatory stimulation of the left PFC. We argue that previously observed positive effects could be false positives and should be interpreted with caution. The findings from the current study thus cast further doubt on the utility of tDCS in enhancing cognitive performance in the healthy (young) brain