Biology subjects

Zaccarella, E.

Publications and source records attributed to Zaccarella, E..

3 recordsLinked to original sources

bioRxiv2021

Towards a causal role of Broca's area in language: A TMS-EEG study on syntactic prediction

Categorical predictions have been proposed as the key mechanism supporting the fast pace of syntactic composition in human language. Accordingly, grammar-based expectations facilitate the analysis of incoming syntactic information--e.g., hearing the determiner "the" enhances the prediction of a noun--which is then checked against a single or few other word categories. Previous functional neuroimaging studies point towards Brocas area in the left inferior frontal gyrus (IFG) as one fundamental cortical region involved in categorical prediction during on-line language processing. Causal evidence for this hypothesis is however still missing. In this study, we combined Electroencephalography (EEG) and Transcranial Magnetic Stimulation (TMS) to test whether Brocas area is functionally relevant in predictive mechanisms for language. Specifically, we transiently perturbed Brocas area during the categorical prediction phase in two-word constructions, while simultaneously measuring the Event-Related Potential (ERP) correlates of syntactic composition. We reasoned that if Brocas area is involved in predictive mechanisms for syntax, disruptive TMS during the processing of the first word (determiner/pronoun) would mitigate the difference in ERP responses for predicted and unpredicted categories when composing basic phrases and sentences. Contrary to our hypothesis, perturbation of Brocas area at the predictive stage did not affect the ERP correlates of basic composition. The correlation strength between the electrical field induced by TMS and the magnitude of the EEG response on the scalp further confirmed this pattern. We discuss the present results in light of an alternative account of the role of Brocas area in syntactic composition, namely the bottom-up integration of words into constituents.

neuroscience↗

bioRxiv2021

Chimpanzees use numerous flexible vocal sequences with more than two vocal units: A step towards language?

A major question in evolutionary science is how did language evolve? Syntax, as the core of language, combines meaning-bearing units (words) into hierarchical structures, thereby creating new meanings. Some other mammals and birds combine meaning-bearing vocalisations, but no documented examples exist of non-human animals combining more than two meaning-bearing vocalisations. Was the two-unit threshold only surpassed in the hominid lineage? Here, we examine the positional patterning of vocal sequences of chimpanzees. We analysed 4826 vocal utterances of 46 wild adult female and male chimpanzees. We found a flexible system with 390 multi-unit vocal sequences, some showing positional or transitional regularities. Two-unit pairs embedded in three-unit sequences predictably occurred either in head or tail positions, and co-occurred with specific other elements. The capacity to organise vocal output beyond the two-unit level may thus exist in species other than humans and could be viewed as an important evolutionary step towards language.

animal behavior and cognition↗

bioRxiv2019

Differential contributions of left-hemispheric language regions to basic semantic composition

Semantic composition, i.e. the ability to combine single words to form complex meanings, is a core feature of human language. Despite growing interest in the basis of semantic composition, the neural correlates and the interaction of regions within this network remain a matter of debate. In the present fMRI study, we designed a well controlled two-word paradigm in which phrases only differed along the semantic dimension while keeping syntactic information alike. 33 healthy participants listened to meaningful phrases ("fresh apple"), anomalous phrases ("awake apple") and pseudoword phrases ("awake gufel") while performing both an implicit and an explicit semantic task. We identified neural signatures for distinct processes during basic semantic composition: The general phrasal composition process, which is independent of the plausibility of the resulting phrase, engages a wide-spread left hemispheric network comprising both executive semantic control regions as well as general conceptual representation regions. Within this network, the functional connectivity between the left anterior inferior frontal gyrus, the bilateral pre-supplementary motor area and the posterior angular gyrus specifically increases during meaningful phrasal composition. The anterior angular gyrus, on the other hand, guides more specific compositional processing evaluating phrasal plausibility. Overall, our results were stronger in the explicit task, pointing towards partly task-dependent involvement of the regions. Here we provide a separation between distinct nodes of the semantic network, whose functional contributions depend on the type of compositional process under analysis. For the first time, we show that the angular gyrus may be decomposable into two sub-regions during semantic composition.

neuroscience↗