Task-related functional connectivity dynamics in a block-designed visual experiment.
Studying task modulations of brain connectivity using functional magnetic resonance imaging (fMRI) is critical to understand brain functions that support cognitive and affective processes. Existing methods such as psychophysiological interaction (PPI) and dynamic causal modeling (DCM) usually implicitly assume that the connectivity patterns are stable over a block-designed task with identical stimuli. However, this assumption lacks empirical verification on high-temporal resolution fMRI data with reliable data-driven analysis methods. The present study performed a detailed examination of dynamic changes of functional connectivity (FC) in a simple block-designed visual checkerboard experiment with a sub-second sampling rate (TR = 0.645 s) by estimating time-varying correlation coefficient (TVCC) between BOLD responses of different brain regions. We observed reliable task-related FC changes (i.e., FCs were transiently decreased after task onset and went back to the baseline afterward) among several visual regions of the bilateral middle occipital gyrus (MOG) and the bilateral fusiform gyrus (FuG). Importantly, only the FCs between higher visual regions (MOG) and lower visual regions (FuG) exhibited such dynamic patterns. The results suggested that simply assuming a sustained FC during a task block may be insufficient to capture distinct task-related FC changes. The investigation of FC dynamics in tasks could improve our understanding of condition shifts and the coordination between different activated brain regions.
Department of Biomedical Engineering, New Jersey Institute of Technology Newark, NJ, USA.
Xin
X
Di
Department of Electrical and Electronic Engineering, The University of Hong Kong Hong Kong, Hong Kong.
Zening
Z
Fu
Department of Electrical and Electronic Engineering, The University of Hong Kong Hong Kong, Hong Kong.
Shing Chow
SC
Chan
Department of Electrical and Electronic Engineering, The University of Hong Kong Hong Kong, Hong Kong.
Yeung Sam
YS
Hung
Department of Biomedical Engineering, New Jersey Institute of Technology Newark, NJ, USA.
Bharat B
BB
Biswal
Department of Electrical and Electronic Engineering, The University of Hong Kong Hong Kong, Hong Kong ; School of Chemical and Biomedical Engineering and School of Electrical and Electronic Engineering, Nanyang Technological University Singapore, Singapore.
Zhiguo
Z
Zhang
dynamic connectivity; functional connectivity; sliding window; time-varying correlation coefficient; visual system