Biology subjects

Vingerhoets, G.

Publications and source records attributed to Vingerhoets, G..

5 recordsLinked to original sources

bioRxiv2025

The individual brain: mapping variability in hemispheric functional organization across cognitive domains in a representative sample

Several core cognitive networks in the human brain show marked left-right differences in their functional organization. While these asymmetries are well described at the level of individual functions, overarching patterns of variability in hemispheric functional organization across multiple domains have not been mapped in a representative sample. To address this gap, we conducted a large-scale neuroimaging study with 200 participants (100 left-handers and 100 right-handers) to map hemispheric phenotypes across four distinct cognitive domains: language, tool use, spatial attention, and face perception. We challenge the traditional one-size-fits-all view of hemispheric organization by showing that deviations from the typical pattern of functional segregation are more prevalent than generally assumed, in both left- and right-handers. As predicted, variation in asymmetry was more pronounced in the left-handed sample. Critically, we found no evidence that the prototypical, "textbook", pattern of brain organization confers any advantage in general cognitive ability or IQ. These results challenge the assumption of a single optimal brain organization and demonstrate that hemispheric functional segregation in humans is much more variable than anticipated.

neuroscience↗

bioRxiv2025

Structural and functional brain asymmetry in relation to heterogeneous causes of situs inversus totalis

Various aspects of brain organization differ between the left and right hemispheres. Clues to the developmental origins of these asymmetries may be gained through associations with situs inversus totalis (SIT), a rare condition in which visceral organs are reversed on the left-right axis. In the largest previous brain imaging analyses of SIT (38 cases, 38 controls from Belgium), typical functional asymmetries such as left-hemisphere language dominance were mostly unaltered, but various aspects of asymmetrical cerebral structure - petalia, bending, and posterior venous anatomy - were often reversed in this condition. SIT can be a monogenic trait that arises from rare genetic variants, usually affecting motile cilia which help to create the embryonic left-right body axis. However, most SIT cases do not have obvious genetic causes and may arise from environmental or random effects during embryogenesis. We sequenced the genomes of 23 SIT cases and 23 controls from the Belgian brain imaging dataset and pooled with prior data from 15 cases and 15 controls. We aimed to discover whether there are altered brain asymmetries in SIT cases with disruptive DNA variants in ciliary genes, or in other types of genes, as compared to genetically unsolved cases. In total, 19 cases had likely causal variants affecting ciliary function, while 19 cases remained genetically unsolved. Functional and structural brain asymmetries were not significantly different in genetically solved versus unsolved SIT cases. Therefore, functional brain asymmetries seem largely independent of known mechanisms of visceral situs formation, while structural brain torque is altered in SIT regardless of the presence or absence of overt genetic causes.

neuroscience↗

bioRxiv2025

Revisiting atypical language lateralization in dyslexia

Hemispheric lateralization has been central to developmental dyslexia research for over a century, yet its role in the etiology of reading and language deficits remains elusive. While altered asymmetries have long been implicated, evidence is inconsistent, with limited consideration given to individual variability in lateralization patterns. This study investigated hemispheric lateralization in 35 adults with dyslexia and 35 matched controls using functional MRI across three language tasks: word generation, rhyming decision, and lexical decision. Laterality indices (LIs) were calculated to comprehensively assess the strength, direction, and consistency of activation across global and regional task-specific brain areas. Significant group differences were not found in the absolute strength of lateralization for global measures or any regional measures, except in the fusiform gyrus, where people with dyslexia showed lower asymmetry. Directional asymmetry was similar across the two groups, except in the fusiform gyrus during the reading task, where dyslexic individuals showed a higher prevalence of right-hemisphere lateralization compared to controls. Interestingly, we found that dyslexic participants demonstrated greater inconsistency in regional lateralization during reading and rhyming tasks. Among individuals with dyslexia, those with inconsistent lateralization in the reading task had weaker fusiform lateralization, although fusiform LI strength itself did not predict reading outcomes. Our findings suggest that dyslexia is characterized by inconsistent, rather than universally weaker, lateralization patterns. Inconsistencies in task-related and regional lateralization may disrupt the efficiency of language networks, contributing to observed reading deficits. By highlighting the role of regional and task-specific inconsistencies, this study provides new insights into the neural mechanisms underlying dyslexia and underscores the importance of considering individual variability in hemispheric lateralization when investigating language disorders.

neuroscience↗

bioRxiv2020

Fibre-specific laterality of white matter in left and right language dominant people

Despite the typical symmetrical appearance of the human brain, several functional and structural asymmetries have been reported. Language is the most commonly described lateralised cognitive function, relying relatively more on the left hemisphere in over 90% of the population. This is in line with white matter studies which have revealed leftwards lateralisation of the arcuate fasciculus, a white matter tract that connects important language-related regions. Most research to date examining the structure-function relationship of language lateralisation only included people showing a left language hemisphere dominance. As such, the reported correlations do not allow for inferences of relationships between the directions of functional and structural lateralisation of language. In this work, we applied a state-of-the-art "fixel-based" analysis approach, which allows to statistically analyse white matter micro- and macrostructure on a fibre-specific level. To study lateralisation using this framework, we defined a bespoke fibre-specific laterality index which allowed us to examine whole-brain white matter asymmetries in samples of participants with left and right language dominance (LLD and RLD respectively). Both groups showed similar extensive and intricate patterns of significant white matter lateralisation. Few group differences were found between both groups, with a similar leftwards lateralisation of the arcuate fasciculus, regardless of functional language lateralisation of the participants. A significant group difference of lateralisation was detected in the forceps minor, with a leftwards lateralisation in LLD and rightwards lateralisation for the RLD group. In conclusion, we showed that fixel-based analysis of fibre-specific lateralisation indices is an effective approach to study white matter asymmetries. Our results suggest that the lateralisation of language functioning and the arcuate fasciculus are driven by independent biases. The exact relationship between forceps minor asymmetry and language dominance could be an interesting subject of future studies.

neuroscience↗

bioRxiv2018

The genetics of situs inversus totalis without primary ciliary dyskinesia

Situs inversus totalis (SIT), a complete left-right mirror reversal of the visceral organs, is usually described as a recessive disorder. SIT can occur with Primary Ciliary Dyskinesia (PCD). However, most people with SIT do not have PCD, and the etiology of their condition remains poorly studied. Those without PCD may have an elevated rate of left-handedness, implying developmental mechanisms linking brain and body laterality. We sequenced the genomes of 15 people with SIT, of which six had PCD, and 15 controls. The SIT subjects with PCD all had likely recessive mutations in genes already known to cause PCD. Two non-PCD SIT cases also had recessive mutations in known PCD genes, suggesting reduced penetrance for PCD in some SIT cases. One non-PCD SIT case had a recessive mutation in PKD1L1, which has previously been linked to SIT without PCD. However, six of the nine non-PCD SIT cases, including most of the left-handers in this dataset, had no obvious candidate genes or significant pathways affected by the mutations that they carried. While we cannot exclude a monogenic basis, more complex genetic models must also be considered, as well as environmental influences or random effects in early development.

genetics↗