Citation

Xie H, Gonzalez-Castillo J, Handwerker DA, Bandettini PA, Calhoun VD, Chen G, Damaraju E, Liu X, Mitra S. Netw. Neurosci. 2018; 3(1): 49-66.

Copyright

(Copyright © 2018, MIT Press)

DOI

10.1162/netn_a_00051

PMID

unavailable

Abstract

Brain functional connectivity (FC), as measured by blood oxygenation level-dependent (BOLD) signal, fluctuates at the scale of 10s of seconds. It has recently been found that whole-brain dynamic FC (dFC) patterns contain sufficient information to permit identification of ongoing tasks. Here, we hypothesize that dFC patterns carry fine-grained information that allows for tracking short-term task engagement levels (i.e., 10s of seconds long). To test this hypothesis, 25 subjects were scanned continuously for 25 min while they performed and transitioned between four different tasks: working memory, visual attention, math, and rest. First, we estimated dFC patterns by using a sliding window approach. Next, we extracted two engagement-specific FC patterns representing active engagement and passive engagement by using k-means clustering. Then, we derived three metrics from whole-brain dFC patterns to track engagement level, that is, dissimilarity between dFC patterns and engagement-specific FC patterns, and the level of brainwide integration level. Finally, those engagement markers were evaluated against windowed task performance by using a linear mixed effects model. Significant relationships were observed between abovementioned metrics and windowed task performance for the working memory task only. These findings partially confirm our hypothesis and underscore the potential of whole-brain dFC to track short-term task engagement levels.

The number of radical Islamist groups fighting in civil wars in Muslim countries has steadily grown over the last twenty years, with such groups outlasting and outperforming more moderate groups. By 2016, Salafi jihadist groups accounted for most of the militant groups in Syria and half of such groups in Somalia. In Iraq, a third of all militant groups were composed of Salafi jihadists. Many analysts argue that the rise of these groups reflects an increase in radical beliefs in Muslim societies. Under certain conditions, however, rebel leaders have strong incentives to embrace an extreme ideology even if they do not believe the ideas that underlie it. When competition is high, information is poor, and institutional constraints are weak, an extremist ideology can help rebel leaders overcome difficult collective-action, principal-agent, and commitment problems. All three of these conditions have been present in the post-2003 civil wars in the Middle East and Africa, and all help explain the emergence and growth of radical groups such as the Islamic State and al-Qaida.


© 2018 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology.

Language: en