Overlapping connectivity patterns during semantic processing of abstract and concrete words revealed with multivariate Granger Causality analysis

Abstract

unlike concrete, nouns refer to notions beyond our perception. even though there is no consensus among linguists as to what exactly constitutes a concrete or abstract word, neuroscientists found clear evidence of a "concreteness" effect. This can, for instance, be seen in patients with language impairments due to brain injury or developmental disorder who are capable of perceiving one category better than another. even though the results are inconclusive, neuroimaging studies on healthy subjects also provide a spatial and temporal account of differences in the processing of abstract versus concrete words. A description of the neural pathways during abstract word reading, the manner in which the connectivity patterns develop over the different stages of lexical and semantic processing compared to that of concrete word processing are still debated. We conducted a high-density eeG study on 24 healthy young volunteers using an implicit categorization task. From this, we obtained high spatio-temporal resolution data and, by means of source reconstruction, reduced the effect of signal mixing observed on scalp level. A multivariate, time-varying and directional method of analyzing connectivity based on the concept of Granger causality (partial Directed coherence) revealed a dynamic network that transfers information from the right superior occipital lobe along the ventral and dorsal streams towards the anterior temporal and orbitofrontal lobes of both hemispheres. Some regions along these pathways appear to be primarily involved in either receiving or sending information. A clear difference in information transfer of abstract and concrete words was observed during the time window of semantic processing, specifically for information transferred towards the left anterior temporal lobe. Further exploratory analysis confirmed a generally stronger connectivity pattern for processing concrete words. We believe our study could guide future research towards a more refined theory of abstract word processing in the brain.Abstract thought and verbal information transfer are two innate cognitive functions of human beings. However, how our brains understand abstract language and how the underlying neural pathways and systems differ from those involved in processing concrete, tangible concepts is not yet clear 1 . Abstract words refer to notions which cannot be touched or sensed, which is why their processing cannot merely rely on the motor and perceptual systems. Experimental data coming from behavioral, neuroimaging (fMRI) and electrophysiological (EEG, MEG) studies of both healthy individuals 2 and patients suffering from brain disorders [3][4][5] show that abstract and concrete words are likely to be processed differently. For example, concrete words have been shown to be learned at an earlier stage of life and understood and retrieved faster 1 . This mechanism is known as the concreteness effect 6,7 . www.nature.com/scientificreports www.nature.com/scientificreports/ frontal electrodes like F7. In this time window, the concre...

Source space reduction for eLORETA

“…Some methods in addition provide estimates of the functional connectivity between reconstructed sources as in BC-VARETA [11], where sources and connectivities are computed simultaneously. A more common approach is to first anatomically define well-separated ROIs and then to estimate their functional connectivity [29] with recent studies pushing for adaptive cortical meshes to improve sensitivity and distinguishability of the ROIs [30]. Others have focused on demixing the recorded signals, instead of localizing them, after which their connectivity is estimated, e.g., using the method proposed in [16].…”

Pre- to Postoperative Longitudinal Follow-up of Phoneme Perception in Glioma Patients: Evidence from the Mismatch Negativity and P300

“…The reported topographical distribution can hardly provide information on neural generators of the ERP and should therefore not be interpreted as such. Increasingly improved techniques for ERP source localization and functional connectivity analysis (Gaudet et al, 2020;Hnazaee et al, 2018;Hnazaee et al, 2020), however, allow the mapping of neural generators and (sub)networks underlying linguistic processes using highdensity EEG. Applying these techniques to pre-and postoperatively collected electrophysiological data could therefore provide a higher precision in the spatial domain in future research.…”

Neural Networks for Directed Connectivity Estimation in Source-Reconstructed EEG Data

“…The standard length of each generated series was 1500 time st for Ground Truth 1 and 2. In Ground Truth 1, three fixed dipoles were used with the directionality of the connections as well as their strength being imposed (Figure 2), a strategy used before [20][21][22]:…”