Distinct neural substrates of visuospatial and verbal-analytic reasoning as assessed by Raven’s Advanced Progressive Matrices

Recent studies revealed spontaneous neural activity to be associated with fluid intelligence (gF) which is commonly assessed by Raven's Advanced Progressive Matrices, and embeds two types of reasoning: visuospatial and verbal-analytic reasoning. With resting-state fMRI data, using global brain connectivity (GBC) analysis which averages functional connectivity of a voxel in relation to all other voxels in the brain, distinct neural correlates of these two reasoning types were found. For visuospatial reasoning, negative correlations were observed in both the primary visual cortex (PVC) and the precuneus, and positive correlations were observed in the temporal lobe. For verbal-analytic reasoning, negative correlations were observed in the right inferior frontal gyrus (rIFG), dorsal anterior cingulate cortex and temporoparietal junction, and positive correlations were observed in the angular gyrus. Furthermore, an interaction between GBC value and type of reasoning was found in the PVC, rIFG and the temporal lobe. These findings suggest that visuospatial reasoning benefits more from elaborate perception to stimulus features, whereas verbal-analytic reasoning benefits more from feature integration and hypothesis testing. In sum, the present study offers, for different types of reasoning in gF, first empirical evidence of separate neural substrates in the resting brain

The role of cognitive reserve in executive functioning and its relationship to cognitive decline and dementia

In this chapter, we explore how cognitive reserve is implicated in coping with the negative consequences of brain pathology and age-related cognitive decline. Individual differences in cognitive performance are based on different brain mechanisms (neural reserve and neural compensation), and reflect, among others, the effect of education, occupational attainment, leisure activities, and social involvement. These cognitive reserve proxies have been extensively associated with efficient executive functioning. We discuss and focus particularly on the compensation mechanisms related to the frontal lobe and its protective role, in maintaining cognitive performance in old age or even mitigating the clinical expression of dementia.info:eu-repo/semantics/publishedVersio

The Role of Cognitive Reserve in Executive Functioning and Its Relationship to Cognitive Decline and Dementia

In this chapter, we explore how cognitive reserve is implicated in coping with the negative consequences of brain pathology and age-related cognitive decline. Individual differences in cognitive performance are based on different brain mechanisms (neural reserve and neural compensation), and reflect, among others, the effect of education, occupational attainment, leisure activities, and social involvement. These cognitive reserve proxies have been extensively associated with efficient executive functioning. We discuss and focus particularly on the compensation mechanisms related to the frontal lobe and its protective role, in maintaining cognitive performance in old age or even mitigating the clinical expression of dementia

Cognitive benefits of exercise interventions: an fMRI activation likelihood estimation meta-analysis

Despite a growing number of functional MRI studies reporting exercise-induced changes during cognitive processing, a systematic determination of the underlying neurobiological pathways is currently lacking. To this end, our neuroimaging meta-analysis included 20 studies and investigated the influence of physical exercise on cognition-related functional brain activation. The overall meta-analysis encompassing all experiments revealed physical exercise-induced changes in the left parietal lobe during cognitive processing. Subgroup analysis further revealed that in the younger-age group (< 35 years old) physical exercise induced more widespread changes in the right hemisphere, whereas in the older-age group (≥ 35 years old) exercise-induced changes were restricted to the left parietal lobe. Subgroup analysis for intervention duration showed that shorter exercise interventions induced changes in regions connected with frontoparietal and default mode networks, whereas regions exhibiting effects of longer interventions connected with frontoparietal and dorsal attention networks. Our findings suggest that physical exercise interventions lead to changes in functional activation patterns primarily located in precuneus and associated with frontoparietal, dorsal attention and default mode networks. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature

A transdiagnostic data-driven study of children's behaviour and the functional connectome.

Behavioural difficulties are seen as hallmarks of many neurodevelopmental conditions. Differences in functional brain organisation have been observed in these conditions, but little is known about how they are related to a child's profile of behavioural difficulties. We investigated whether behavioural difficulties are associated with how the brain is functionally organised in an intentionally heterogeneous and transdiagnostic sample of 957 children aged 5-15. We used consensus community detection to derive data-driven profiles of behavioural difficulties and constructed functional connectomes from a subset of 238 children with resting-state functional Magnetic Resonance Imaging (fMRI) data. We identified three distinct profiles of behaviour that were characterised by principal difficulties with hot executive function, cool executive function, and learning. Global organisation of the functional connectome did not differ between the groups, but multivariate patterns of connectivity at the level of Intrinsic Connectivity Networks (ICNs), nodes, and hubs significantly predicted group membership in held-out data. Fronto-parietal connector hubs were under-connected in all groups relative to a comparison sample and children with hot vs cool executive function difficulties were distinguished by connectivity in ICNs associated with cognitive control, emotion processing, and social cognition. This demonstrates both general and specific neurodevelopmental risk factors in the functional connectome

Patients with Alzheimer's disease dementia show partially preserved parietal 'hubs' modeled from resting-state alpha electroencephalographic rhythms

IntroductionGraph theory models a network by its nodes (the fundamental unit by which graphs are formed) and connections. 'Degree' hubs reflect node centrality (the connection rate), while 'connector' hubs are those linked to several clusters of nodes (mainly long-range connections). MethodsHere, we compared hubs modeled from measures of interdependencies of between-electrode resting-state eyes-closed electroencephalography (rsEEG) rhythms in normal elderly (Nold) and Alzheimer's disease dementia (ADD) participants. At least 5 min of rsEEG was recorded and analyzed. As ADD is considered a 'network disease' and is typically associated with abnormal rsEEG delta (<4 Hz) and alpha rhythms (8-12 Hz) over associative posterior areas, we tested the hypothesis of abnormal posterior hubs from measures of interdependencies of rsEEG rhythms from delta to gamma bands (2-40 Hz) using eLORETA bivariate and multivariate-directional techniques in ADD participants versus Nold participants. Three different definitions of 'connector' hub were used. ResultsConvergent results showed that in both the Nold and ADD groups there were significant parietal 'degree' and 'connector' hubs derived from alpha rhythms. These hubs had a prominent outward 'directionality' in the two groups, but that 'directionality' was lower in ADD participants than in Nold participants. DiscussionIn conclusion, independent methodologies and hub definitions suggest that ADD patients may be characterized by low outward 'directionality' of partially preserved parietal 'degree' and 'connector' hubs derived from rsEEG alpha rhythms

Patients with Alzheimer’s disease dementia show partially preserved parietal ‘hubs’ modeled from resting-state alpha electroencephalographic rhythms

Introduction: Graph theory models a network by its nodes (the fundamental unit by which graphs are formed) and connections. ‘Degree’ hubs reflect node centrality (the connection rate), while ‘connector’ hubs are those linked to several clusters of nodes (mainly long-range connections). Methods: Here, we compared hubs modeled from measures of interdependencies of between-electrode resting-state eyes-closed electroencephalography (rsEEG) rhythms in normal elderly (Nold) and Alzheimer’s disease dementia (ADD) participants. At least 5 min of rsEEG was recorded and analyzed. As ADD is considered a ‘network disease’ and is typically associated with abnormal rsEEG delta (<4 Hz) and alpha rhythms (8–12 Hz) over associative posterior areas, we tested the hypothesis of abnormal posterior hubs from measures of interdependencies of rsEEG rhythms from delta to gamma bands (2–40 Hz) using eLORETA bivariate and multivariate-directional techniques in ADD participants versus Nold participants. Three different definitions of ‘connector’ hub were used. Results: Convergent results showed that in both the Nold and ADD groups there were significant parietal ‘degree’ and ‘connector’ hubs derived from alpha rhythms. These hubs had a prominent outward ‘directionality’ in the two groups, but that ‘directionality’ was lower in ADD participants than in Nold participants. Discussion: In conclusion, independent methodologies and hub definitions suggest that ADD patients may be characterized by low outward ‘directionality’ of partially preserved parietal ‘degree’ and ‘connector’ hubs derived from rsEEG alpha rhythms

Neural mechanisms of cognitive reserve in Alzheimer's disease

Alzheimer’s disease (AD) is the most common cause of age-related dementia, where neuropathological changes develop gradually over years before the onset of dementia symptoms. Yet, despite the progression of AD pathology, the decline in cognitive abilities such as episodic memory can be relatively slow. A slower decline of cognition and delayed onset of dementia relative to the progression of neuropathology has been associated with particular intellectual and lifestyle factors such as more years of education and IQ. Thus education and IQ are seen as protective factors that are associated with an increased ability to cope with brain pathology, i.e. cognitive reserve. While numerous studies showed that education, IQ and other lifestyle factors are associated with relatively high cognitive abilities in AD, little is known about the underlying brain mechanisms of reserve. Most previous studies tested the association between protective factors such as education or IQ and differences in brain structure and function in order to identify brain mechanisms underlying reserve. Since such protective factors are global in nature and unspecific with regard to reserve, the results were highly variable. So far, there is a lack of knowledge of brain features that are associated with a higher ability to maintain cognition in the face of AD pathology. The overall aim of this dissertation was to test a priori selected functional network features that may underlie cognitive reserve. We focused on resting-state functional networks, and in particular the fronto-parietal control network as correlate of cognitive reserve. Such functional networks are thought to be composed of brain regions that are co-activated during a particular task, where the interaction between brain regions may be critical to support cognitive function. During task-free resting-state periods, the different and often distant brain regions of such network show correlated activity, i.e. functional connectivity. For the fronto-parietal control network, and in particular its globally connected hub in the left frontal cortex (LFC), higher resting-state connectivity has been previously shown to be associated with higher cognitive abilities as well as higher education and IQ, i.e. protective factors associated with reserve. Since that network and its LFC hub are relatively spared in AD, in contrast to more posterior parietal networks, we investigated whether higher connectivity of the fronto-parietal control network is associated with higher reserve in AD. We argued that the fronto-parietal control network is relatively stable during the initial stages of AD and may thus be well posited to subserve reserve in AD. In contrast, networks like the default mode network (DMN) that cover midline brain structures including the medial frontal lobe and the posterior cingulate may be highly vulnerable to AD pathology, given the previous observations of altered DMN connectivity and posterior parietal FDG-PET hypometabolism in AD. In particular, the resting-state connectivity between the DMN and the dorsal attention network (DAN) may be predictive of lower episodic memory in AD. Both networks interact in a competitive (i.e. anti-correlated) way during task and resting-state, which is critical for cognitive processes such as episodic memory. In a first step, we tested whether the resting-state connectivity between the DMN and theDAN (i.e. anti-correlated activity) is associated with lower episodic memory in subjects with amnestic mild cognitive impairment (MCI), i.e. subjects at increased risk to convertto AD dementia. Furthermore, we tested whether protective factors such as higher education moderate the association between the DMN-DAN anti-correlation andcognition. Here, the DMN-DAN anti-correlation was a measure of AD relatedpathological change rather than a substrate of reserve.We could show in two independent samples of patients at risk of AD dementia that a weaker DMN-DAN anti-correlation was associated with lower episodic memory, where the decrements in episodic memory were however weaker in subjects with higher education or IQ (interaction DMN-DAN x education/IQ). These results suggest that MCI subjects with higher protective factors (education, IQ) maintain episodic memory relatively well at a given level of AD-related brain changes. In the second step, we sought to identify those network differences that support cognitive reserve, i.e. that may explain the association between higher education and milder cognitive impairment in AD. Here, we could show that greater resting-state fMRI assessed global connectivity of the LFC, i.e. a key hub of the fronto-parietal control network, was associated with greater education and attenuated effects of neurodegeneration (measured by parietal FDG-PET hypometabolism) on memory in prodromal AD. Together, these results support the idea that global connectivity of a fronto-parietal control network hub supports cognitive reserve in AD. Based on this finding, we developed a novel restingstate fMRI index of fronto-parietal control network connectivity as a functional imaging marker of cognitive reserve. This marker is highly correlated with education and may thus be used as an imaging-based index of cognitive reserve. Together, our results provide for the first time evidence that cognitive reserve in AD is supported by higher functional connectivity of the fronto-parietal control network, in particular its LFC hub