Static and dynamic measures of human brain connectivity predict complementary aspects of human cognitive performance

In cognitive network neuroscience, the connectivity and community structure of the brain network is related to cognition. Much of this research has focused on two measures of connectivity - modularity and flexibility - which frequently have been examined in isolation. By using resting state fMRI data from 52 young adults, we investigate the relationship between modularity, flexibility and performance on cognitive tasks. We show that flexibility and modularity are highly negatively correlated. However, we also demonstrate that flexibility and modularity make unique contributions to explain task performance, with modularity predicting performance for simple tasks and flexibility predicting performance on complex tasks that require cognitive control and executive functioning. The theory and results presented here allow for stronger links between measures of brain network connectivity and cognitive processes.Comment: 37 pages; 7 figure

Brain Modularity Mediates the Relation between Task Complexity and Performance

Recent work in cognitive neuroscience has focused on analyzing the brain as a network, rather than as a collection of independent regions. Prior studies taking this approach have found that individual differences in the degree of modularity of the brain network relate to performance on cognitive tasks. However, inconsistent results concerning the direction of this relationship have been obtained, with some tasks showing better performance as modularity increases and other tasks showing worse performance. A recent theoretical model (Chen & Deem, 2015) suggests that these inconsistencies may be explained on the grounds that high-modularity networks favor performance on simple tasks whereas low-modularity networks favor performance on more complex tasks. The current study tests these predictions by relating modularity from resting-state fMRI to performance on a set of simple and complex behavioral tasks. Complex and simple tasks were defined on the basis of whether they did or did not draw on executive attention. Consistent with predictions, we found a negative correlation between individuals' modularity and their performance on a composite measure combining scores from the complex tasks but a positive correlation with performance on a composite measure combining scores from the simple tasks. These results and theory presented here provide a framework for linking measures of whole brain organization from network neuroscience to cognitive processing.Comment: 47 pages; 4 figure

THE RELATIONSHIP AMONG GRAY MATTER CORTICAL THICKNESS, ACTIVITY, AND BILINGUAL BACKGROUND VARIABLES

A bilingual person’s brain has to manage two languages. According to psycholinguistic models, lexical representations of the two languages are always active and to select the correct language, the other has to be inhibited (Green, 1998). This includes cognitive control processes (e.g. language planning, response inhibition, maintenance of representation) that might require additional brain networks beyond those classically involved in language processing. Regions such as prefrontal, anterior cingulate cortices, inferior parietal lobule, and caudate have been found to be involved in cognitive control processes (Abutalebi & Green, 2007). The present study examined whether or not bilingual experience shapes the structure and function of the brain by examining relationships among language proficiency, second language age of acquisition, and structural and functional correlates. Participants were 49 Spanish-English bilinguals who learned English between the ages of 0 and 17 years. Cortical thickness measures as well as functional activity during a picture-naming task requiring switching between the two languages on a trial-by-trial basis were acquired using a functional Magnetic Resonance Imaging scanner. The results indicate that age of acquisition of the second language but not proficiency is related to gray matter structure in the right dorsolateral prefrontal cortex, a cognitive control region and that gray matter cortical thickness is related to functional activity during a condition that requires switching in naming pictures between two languages. These results carry implications for the understanding of how language experience shapes the functional and neural correlates of the bilingual brain.Psychology, Department o

INVESTIGATING THE NEURAL CORRELATES OF LANGUAGE SWITCHING IN SPANISH ENGLISH BILINGUALS EMPLOYING EFFECTIVE CONNECTIVITY ANALYSES

Bilingualism requires individuals to manage their two languages in order to communicate with others. They may voluntarily or involuntarily switch back and forth between their two languages. While voluntarily switching between two languages may appear effortless, it requires a tremendous amount of cognitive effort. Previous imaging and language impairment research has shown evidence of a cognitive control mechanism needed for switching between two languages that involves areas such as prefrontal cortex, inferior parietal cortex, anterior cingulate cortex and basal ganglia. This mechanism has been identified as being involved in executive function processes (e.g. working memory, conflict monitoring, set switching and language selection). While previous imaging studies have identified brain areas showing increased activation during language switching tasks, they do not discuss how these areas interact with each other in the healthy bilingual brain. The purpose of this study was to investigate whether or not brain regions involved in the cognitive control processes needed in bilingualism exert influence on each other and how different conditions modulate such connections. Twenty healthy right-handed Spanish-English bilinguals (13 women) between the ages of 18 and 32 participated in an fMRI experiment. Participants overtly named objects in three conditions: Spanish only, English only and mixed (alternating between Spanish and English) in a picture-naming task while inside the scanner. Three cognitive control regions (e.g. prefrontal, parietal, and caudate) and an object recognition region (e.g. fusiform gyrus) were chosen to be included in Dynamic Causal Modeling (DCM) analyses. Three models were created to examine differential modulatory effects of the conditions on the interactions between cognitive control and object recognition regions. Bayesian Model Selection using DCM revealed that the English and Spanish conditions modulated the interactions between the cognitive control and object recognition regions more so than the mixed condition. These results indicated that the three conditions had a differential modulatory effect on brain connections, suggesting that the cognitive control network required for naming is more strongly connected during naming solely in English or Spanish than during naming in the language-switching mixed condition. Is possible that these bilinguals are not used to switching back and forth between their two languages. These findings carry implications for both the bilingual literature in general and the bilingual aphasia literature.Psychology, Department o

Static and Dynamic Measures of Human Brain Connectivity Predict Complementary Aspects of Human Cognitive Performance

In cognitive network neuroscience, the connectivity and community structure of the brain network is related to measures of cognitive performance, like attention and memory. Research in this emerging discipline has largely focused on two measures of connectivity—modularity and flexibility—which, for the most part, have been examined in isolation. The current project investigates the relationship between these two measures of connectivity and how they make separable contribution to predicting individual differences in performance on cognitive tasks. Using resting state fMRI data from 52 young adults, we show that flexibility and modularity are highly negatively correlated. We use a Brodmann parcellation of the fMRI data and a sliding window approach for calculation of the flexibility. We also demonstrate that flexibility and modularity make unique contributions to explain task performance, with a clear result showing that modularity, not flexibility, predicts performance for simple tasks and that flexibility plays a greater role in predicting performance on complex tasks that require cognitive control and executive functioning. The theory and results presented here allow for stronger links between measures of brain network connectivity and cognitive processes

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care