Identifying dynamic effective connectivity states in fMRI based on time-varying vector autoregressive models

S. Balqis Samdin, C. M. Ting, S. H. Salleh, M. Hamedi, A. M. Noor

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3 Citations (Scopus)


We propose a framework to estimate the transition of effective connectivity states in functional magnetic resonance imaging (fMRI), with the changing experimental conditions. The fMRI effective connectivity is traditionally assumed to be stationary across the entire scanning timecourse. However, recent evidence shows that it exhibits dynamic changes over time. In this study, we employ a non-stationary model based on time-varying autoregression (TV-VAR) to capture the dynamic effective connectivity, and K-means clustering to identify the change-points of the connectivity states. The TV-VAR parameters are estimated sequentially in time using the Kalman filtering and the expectation- maximization (EM) algorithm. The extracted directed connectivities between brain regions are then used as features to the K-means algorithm to be partitioned into a finite number of states and to produce the state change-points, assuming the task condition boundaries are unknown. Experimental results on motor-task fMRI data show the ability of the proposed method in estimating the state-related changes in the motor regions during the resting-state and active conditions, with low squared estimation errors. The estimated brain-state connectivity also reveals different patterns between the healthy subjects and the stroke patients.

Original languageEnglish
Title of host publicationInternational Conference for Innovation in Biomedical Engineering and Life Sciences
EditorsFatimah Ibrahim, Mas Sahidayana Mohktar, Mohd Yazed Ahmad, Juliana Usman
Number of pages5
ISBN (Print)9789811002656
Publication statusPublished - 2015
Externally publishedYes
EventInternational Conference for Innovation in Biomedical Engineering and Life Sciences 2015 - Putrajaya, Malaysia
Duration: 6 Dec 20158 Dec 2015 (Proceedings)

Publication series

NameIFMBE Proceedings
ISSN (Print)1680-0737


ConferenceInternational Conference for Innovation in Biomedical Engineering and Life Sciences 2015
Abbreviated titleICIBEL 2015
Internet address


  • Dynamic Brain Connectivity
  • FMRI
  • Kalman Filters
  • State-space Models
  • Vector Autoregressive Model

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