Biology subjects

Klaus, J.

Publications and source records attributed to Klaus, J..

3 recordsLinked to original sources

bioRxiv2017

The Role of Left Dorsolateral Prefrontal Cortex in Language Processing

In addition to the role of left frontotemporal areas in language processing, there is increasing evidence that language comprehension and production require control and working memory resources involving the left dorsolateral prefrontal cortex (DLPFC). The aim of this study was to investigate the role of the left DLPFC in both language comprehension and production. In a double-blind, sham-controlled crossover experiment, thirty-two participants received cathodal or sham transcranial direct current stimulation (tDCS) to the left DLPFC while performing a language comprehension and a language production task. Results showed that cathodal tDCS increases reaction times in the language comprehension task, but decreases naming latencies in the language production task. However, additional analyses revealed that the polarity of tDCS effects was highly correlated across tasks, implying differential individual susceptibility to the effect of tDCS within participants. Overall, our findings demonstrate that left DLPFC is part of the complex cortical network associated with language processing.

neuroscience↗

bioRxiv2017

Putting Focus on Transcranial Direct Current Stimulation in Language Production Studies

ObjectivePrevious language production studies targeting the inferior frontal and superior temporal gyrus using anodal tDCS have provided mixed results. Part of this heterogeneity may be explained by limited target region focality of conventionally used electrode montages. We examined the focality of conventionally and alternative electrode montages.\n\nMethodsElectrical field distributions of anodal tDCS targeting IFG and pSTG were simulated in conventional setups (anodal electrode over IFG/pSTG, reference electrode over right supraorbital region) and an alternative electrode montage in four different brains.\n\nResultsConventional montages showed maximum field strengths outside of the target regions. Results from alternative electrode montages showed that focality of tDCS could be improved by adjustments in electrode size and placement.\n\nConclusionsHeterogeneity of findings of language production studies deploying conventional tDCS montages may in part be explained by diffuse electrical field distributions. Alternative montages may improve focality and provide more unequivocal results.\n\nSignificanceReliability of tDCS in language production research, both in basic and applied fields, can be improved by adopting different electrode montages which target the region of interest in a more direct way.

neuroscience↗

bioRxiv2017

Non-Invasive Brain Stimulation to Investigate Language Production in Healthy Speakers: A Review and Meta-Analysis

Non-invasive brain stimulation (NIBS) has become a common method to study the interrelations between the brain and language functioning. This meta-analysis examined the efficacy of transcranial magnetic stimulation (TMS) and direct current stimulation (tDCS) in the study of language production in healthy volunteers. Forty-five effect sizes from 30 studies which investigated the effects of NIBS on picture naming or verbal fluency in healthy participants were meta-analysed. Further sub-analyses investigated potential influences of stimulation type, control, target site, task, online vs. offline application, and current density of the target electrode. Random effects modelling showed a small, but reliable effect of NIBS on language production. Subsequent analyses indicated larger weighted mean effect sizes for TMS as compared to tDCS studies. No statistical differences for the other sub-analyses were observed. We conclude that NIBS is a useful method for neuroscientific studies on language production in healthy volunteers.

neuroscience↗