Increased cognitive complexity reveals abnormal brain network activity in individuals with corpus callosum dysgenesis

Abstract

Cognitive reasoning is thought to require functional interactions between whole-brain networks. Such networks rely on both cerebral hemispheres, with the corpus callosum providing cross-hemispheric communication. Here we used high-field functional magnetic resonance imaging (7 T fMRI), a well validated cognitive task, and brain network analyses to investigate the functional networks underlying cognitive reasoning in individuals with corpus callosum dysgenesis (CCD), an anatomical abnormality that affects the corpus callosum. Participants with CCD were asked to solve cognitive reasoning problems while their brain activity was measured using fMRI. The complexity of these problems was parametrically varied by changing the complexity of relations that needed to be established between shapes within each problem matrix. Behaviorally, participants showed a typical reduction in task performance as problem complexity increased. Task-evoked neural activity was observed in brain regions known to constitute two key cognitive control systems: the fronto-parietal and cingulo-opercular networks. Under low complexity demands, network topology and the patterns of local neural activity in the CCD group closely resembled those observed in neurotypical controls. By contrast, when asked to solve more complex problems, participants with CCD showed a reduction in neural activity and connectivity within the fronto-parietal network. These complexity-induced, as opposed to resting-state, differences in functional network activity help resolve the apparent paradox between preserved network architecture found at rest in CCD individuals, and the heterogeneous deficits they display in response to cognitive task demands [preprint: https://doi.org/10.1101/312629].

Reconfiguration of functional brain networks and metabolic cost converge during task performance

“…Although the physiological mechanisms coupling CBF and CMRGlu most likely remain the same, our findings indicate that the time-dependent, nonlinear interactions between synaptic processing, energy consumption and neurovascular responses across macroscopic brain regions become apparent when engaging in a cognitively demanding task. The ability of functionally specialized brain regions to dynamically change their connectivity patterns is essential for cognitive processing (Cocchi et al, 2013;Cole et al, 2013;Hearne et al, 2019). Our results extend this knowledge by highlighting that external task engagement is accompanied by the convergence between metabolic factors and functional brain network reconfigurations.…”

Development and plasticity of the corpus callosum

“…Sixty-five to 75% of isolated cAgCC cases show no apparent neurological defects (Santo et al, 2012;Bayram et al, 2020). When defects are present, they are frequently related to motor difficulties, deficits in problem solving, social skills or language problems (Marsh et al, 2018;Edwards et al, 2014;Hearne et al, 2019). Interestingly, individuals with developmental cAgCC demonstrate better bilateral processing than individuals that experience surgical sectioning of the CC as adults (Edwards et al, 2014).…”

Intra- and Inter-individual Variability of Executive Functions: Determinant and Modulating Factors in Healthy and Pathological Conditions

“…Furthermore, activation in the MD network is found when individuals perform fluid intelligence tests (Duncan et al, 2000). Interestingly, increasing complexity in nonverbal reasoning tasks has recently been associated with abnormal MD network activation in individuals with developmental corpus callosal dysgenesis (Hearne et al, 2018). These findings suggest that it may be a decline in fluid intelligence which underlies the EF impairments reported in frontal patients.…”