The role of functional and structural interhemispheric auditory connectivity for language lateralization - A combined EEG and DTI study

Abstract

Interhemispheric connectivity between auditory areas is highly relevant for normal auditory perception and alterations are a major factor for the development of auditory verbal hallucinations. Surprisingly, there is no combined EEG-DTI study directly addressing the role of functional and structural connectivity in the same group of subjects. Accordingly, nothing is known about the relationship between functional connectivity such as gamma-band synchrony, structural integrity of the interhemispheric auditory pathways (IAPs) and language lateralization as well as whether the gamma-band synchrony is configured on the backbone of IAPs. By applying multimodal imaging of 64-channel EEG and DTI tractography, we investigated in 27 healthy volunteers the functional gamma-band synchrony between either bilateral primary or secondary auditory cortices from eLORETA source-estimation during dichotic listening, as well as the correspondent IAPs from which fractional anisotropy (FA) values were extracted. Correlation and regression analyses revealed highest values for gamma-band synchrony, followed by FA for secondary auditory cortices, which were both significantly related to a reduced language lateralization. There was no such association between the white-matter microstructure and gamma-band synchrony, suggesting that structural connectivity might also be relevant for other (minor) aspects of information transfer in addition to gamma-band synchrony, which are not detected in the present coupling analyses. The combination of multimodal EEG-DTI imaging provides converging evidence of neural correlates by showing that both stronger pathways and increased gamma-band synchrony within one cohort of subjects are related to a reduced leftward-lateralization for language.

Revisiting correlation-based functional connectivity and its relationship with structural connectivity

“…For example, it was shown that brain function is primarily shaped by anatomical modes computed from the spectral properties of the SC matrix (Abdelnour, Dayan, Devinsky, Thesen, & Raj, 2018 ; Atasoy, Donnelly, & Pearson, 2016 ; Huang et al, 2018 ; Preti & Van De Ville, 2019 ; Robinson, 2012 ). Finally, as most studies use functional magnetic resonance imaging (fMRI) data to evaluate FC because of its high spatial resolution, other functional modalities such as electro- or magneto-encephalography were also considered to explore the link between brain anatomy and function (Amico et al, 2017 ; Finger et al, 2016 ; Steinmann et al, 2018 ).…”

Corpus callosum morphology across the lifespan in baboons (Papio anubis): a cross-sectional study of relative mid-sagittal surface area and thickness

“…Further exploring the data by also considering uncorrected p-values, revealed a cluster of segments in the splenium of the corpus callosum which showed an association with age of medium to large effect sizes (between 6 and 10% explained variance). The splenium is thought to connect sensory cortices or parietal brain regions (Schmahmann & Pandya, 2006), suggesting a relationship of the aging effect to the development of sensory or attentional integration between the hemispheres (e.g., Bozzali et al, 2012; Steinmann et al, 2018). Interestingly, here the aging trajectory resembled a saturation function: a rapid increase from childhood to adulthood is followed by a period of constant thickness that reaches into old age.…”

“…The corpus callosum as the major white-matter commissure, is a critical channel for the integration of information (e.g., Steinmann et al, 2018; Westerhausen, Gruner, Specht, & Hugdahl, 2009) and coordination of processing in the two cerebral hemisphere (e.g., Davis & Cabeza, 2015; Thiel et al, 2006). Thus, it appears little surprising that human neuroimaging studies report an association of individual differences in corpus callosum morphology with differences in higher cognitive abilities (e.g., Danielsen et al, 2020; Dunst, Benedek, Koschutnig, Jauk, & Neubauer, 2014; Hulshoff-Pol et al, 2006; Luders et al, 2007; Westerhausen et al, 2018).…”

Disrupted neural synchrony mediates the relationship between white matter integrity and cognitive performance in older adults

“…Resting-state EEG connectivity partly depends on the underlying white matter tract architecture 23,24,25,26 . With aging, even small changes in white matter integrity might lead to delayed and/or altered communications between brain regions, which could in turn alter cognitive functioning.…”