A tale of two gradients: differences between the left and right hemispheres predict semantic cognition

• Published in: Brain Structure and Function Vol. 227; no. 2; pp. 631 - 654
• Main Authors: Gonzalez Alam, Tirso Rene del Jesus, Mckeown, Brontë L. A., Gao, Zhiyao, Bernhardt, Boris, Vos de Wael, Reinder, Margulies, Daniel S., Smallwood, Jonathan, Jefferies, Elizabeth
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2022; Springer Nature B.V; Springer Verlag
• Subjects: Attention; Biomedical and Life Sciences; Biomedicine; Brain - diagnostic imaging; Brain Mapping; Cell Biology; Cerebral hemispheres; Cognition; Cognition & reasoning; Cognitive Sciences; Cortex (somatosensory); Functional Laterality; Functional magnetic resonance imaging; Hemispheric laterality; Humans; Language; Life Sciences; Luteinizing hormone; Magnetic Resonance Imaging; Memory; Memory, Short-Term; Neural networks; Neurology; Neurons and Cognition; Neurosciences; Original; Original Article; Semantics; Sensorimotor Cortex; Short term memory; Visual perception; fMRI; Gradients; Intrinsic connectivity; Hemispheric specialization; Laterality; Semantic cognition
• ISSN: 1863-2653; 1863-2661; 1863-2661; 0340-2061
• DOI: 10.1007/s00429-021-02374-w

Decomposition of whole-brain functional connectivity patterns reveals a principal gradient that captures the separation of sensorimotor cortex from heteromodal regions in the default mode network (DMN). Functional homotopy is strongest in sensorimotor areas, and weakest in heteromodal cortices, suggesting there may be differences between the left and right hemispheres (LH/RH) in the principal gradient, especially towards its apex. This study characterised hemispheric differences in the position of large-scale cortical networks along the principal gradient, and their functional significance. We collected resting-state fMRI and semantic, working memory and non-verbal reasoning performance in 175 + healthy volunteers. We then extracted the principal gradient of connectivity for each participant, tested which networks showed significant hemispheric differences on the gradient, and regressed participants’ behavioural efficiency in tasks outside the scanner against interhemispheric gradient differences for each network. LH showed a higher overall principal gradient value, consistent with its role in heteromodal semantic cognition. One frontotemporal control subnetwork was linked to individual differences in semantic cognition: when it was nearer heteromodal DMN on the principal gradient in LH, participants showed more efficient semantic retrieval—and this network also showed a strong hemispheric difference in response to semantic demands but not working memory load in a separate study. In contrast, when a dorsal attention subnetwork was closer to the heteromodal end of the principal gradient in RH, participants showed better visual reasoning. Lateralization of function may reflect differences in connectivity between control and heteromodal regions in LH, and attention and visual regions in RH.