Acquisition of concrete and abstract words is modulated by tDCS of Wernicke’s area

Abstract

Previous behavioural and neuroimaging research suggested distinct cortical systems involved in processing abstract and concrete semantics; however, there is a dearth of causal evidence to support this. To address this, we applied anodal, cathodal, or sham (placebo) tDCS over Wernicke’s area before a session of contextual learning of novel concrete and abstract words (n = 10 each), presented five times in short stories. Learning effects were assessed at lexical and semantic levels immediately after the training and, to attest any consolidation effects of overnight sleep, on the next day. We observed successful learning of all items immediately after the session, with decreased performance in Day 2 assessment. Importantly, the results differed between stimulation conditions and tasks. Whereas the accuracy of semantic judgement for abstract words was significantly lower in the sham and anodal groups on Day 2 vs. Day 1, no significant performance drop was observed in the cathodal group. Similarly, the cathodal group showed no significant overnight performance reduction in the free recall task for either of the stimuli, unlike the other two groups. Furthermore, between-group analysis showed an overall better performance of both tDCS groups over the sham group, particularly expressed for abstract semantics and cathodal stimulation. In sum, the results suggest overlapping but diverging brain mechanisms for concrete and abstract semantics and indicate a larger degree of involvement of core language areas in storing abstract knowledge. Furthermore, they demonstrate a possiblity to improve learning outcomes using neuromodulatory techniques.

Contextual Acquisition of Concrete and Abstract Words: Behavioural and Electrophysiological Evidence

“…As a result, of all tasks applied, only the free-form definition quality showed a marginal ( p = 0.084) concreteness effect; this may have more to do with the nature of this task and the relative ease of defining concrete objects as opposed to abstract ones, rather than differences in learning per se. This finding is corroborated by a recent study [ 32 ], which used a similarly controlled design and also found only very limited evidence of concreteness effect in a semantic task. Combined, these results suggest that the concreteness effect, known from studies of existing words, may, to some degree at least, be explained by non-semantic factors such as different psycholinguistic properties (length, frequency of occurrence), age and mode of acquisition, and other variables, rather than the concreteness/abstractness as such.…”

“…Additionally, as the present results are limited to Russian language and participant sample, they should in the future be verified using other samples and languages; it would be useful for such future studies to use preregistration of their hypotheses to make the research more transparent and replicable. Moreover, a neuromodulation approach using the same paradigm in conjunction with non-invasive brain stimulation methods (such as tDCS or TMS) may help to clarify the causal structure-function relationship in future studies [ 1 , 32 , 63 ] . Finally, another direction of further research could be investigating of acquisition of different semantic sub types (for instance, artificial and natural objects, emotional, social, and numerical concepts), which were beyond the scope of the current study, which was chiefly focussed on a comparison of learning between abstract and concrete semantics on a more general level, as well as being restricted by the technical and paradigmatic limits inherent to such an experiment.…”

“…We used a comprehensive set of tasks to assess the acquisition of new words at both lexical and semantic levels as well as EEG recordings of brain responses to newly acquired words to scrutinise the neural activity of their newly established representations. We expected to find differences in the processing of two semantic types in ERPs, which may be underpinned by the stronger involvement of core language systems in abstract word representations [ 32 ]. We also predicted that potentially more laborious abstract word acquisition could engage more widespread brain regions than concrete words including activation of prefrontal and temporoparietal areas.…”

Electrophysiological Evidence of Dissociation Between Explicit Encoding and Fast Mapping of Novel Spoken Words

“…That said, the use of such methods as EEG or fMRI cannot establish causal relationships between the brain structures and their function and thus only indicates indirect links between neural activity and behavior. Future studies could therefore also use non-invasive neurostimulation approaches, such as TMS or tDCS, to test the causal nature of involvement of specific brain areas in particular word learning mechanisms (Vukovic and Shtyrov, 2019;Kurmakaeva et al, 2021).…”

That means something to me: the effect of linguistic and emotional experience on the acquisition and processing of novel abstract concepts

“…Therefore, it is questionable whether in these studies, the linguistic training induced novel word representations or whether it induced only a novel label for already existing concepts. To our knowledge, only two recently published studies from the same working group induced truly novel (in form and semantic content) concrete and abstract word meanings in a purely linguistic training paradigm (Kurmakaeva et al, 2021;Mkrtychian et al, 2021). After one training session with contextual learning from five-sentence short stories, they found a higher free recall accuracy and shorter LDT reaction times for abstract than concrete words, and that stimulating core language areas with tDCS specifically supports storing abstract knowledge.…”