Identifying functional co-activation patterns in neuroimaging studies via poisson graphical models

Biometrics. 2014 Dec;70(4):812-22. doi: 10.1111/biom.12216. Epub 2014 Aug 21.


Studying the interactions between different brain regions is essential to achieve a more complete understanding of brain function. In this article, we focus on identifying functional co-activation patterns and undirected functional networks in neuroimaging studies. We build a functional brain network, using a sparse covariance matrix, with elements representing associations between region-level peak activations. We adopt a penalized likelihood approach to impose sparsity on the covariance matrix based on an extended multivariate Poisson model. We obtain penalized maximum likelihood estimates via the expectation-maximization (EM) algorithm and optimize an associated tuning parameter by maximizing the predictive log-likelihood. Permutation tests on the brain co-activation patterns provide region pair and network-level inference. Simulations suggest that the proposed approach has minimal biases and provides a coverage rate close to 95% of covariance estimations. Conducting a meta-analysis of 162 functional neuroimaging studies on emotions, our model identifies a functional network that consists of connected regions within the basal ganglia, limbic system, and other emotion-related brain regions. We characterize this network through statistical inference on region-pair connections as well as by graph measures.

Keywords: EM algorithm; Emotion; Functional brain networks; Functional co-activation pattern identification; Poisson Graphical Model.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Brain / physiology*
  • Brain Mapping / methods*
  • Computer Simulation
  • Emotions / physiology*
  • Humans
  • Magnetic Resonance Imaging / methods
  • Models, Neurological
  • Models, Statistical*
  • Nerve Net / physiology*
  • Pattern Recognition, Automated / methods*
  • Poisson Distribution
  • Reproducibility of Results
  • Sensitivity and Specificity