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Neuroimage. 2020 Feb 25;212:116635. doi: 10.1016/j.neuroimage.2020.116635. [Epub ahead of print]

Time-resolved effective connectivity in task fMRI: Psychophysiological interactions of Co-Activation patterns.

Author information

1
Institute of Bioengineering, École Polytechnique Fédérale de Lausanne, Switzerland; Department of Radiology and Medical Informatics, University of Geneva, Switzerland; Division of Development and Growth, Department of Pediatrics, University of Geneva, Switzerland. Electronic address: lorena.freitas@epfl.ch.
2
Institute of Bioengineering, École Polytechnique Fédérale de Lausanne, Switzerland; Department of Radiology and Medical Informatics, University of Geneva, Switzerland.
3
Department of Physics, University of Bristol, United Kingdom.
4
Department of Basic Neurosciences, University of Geneva, Switzerland.
5
Division of Development and Growth, Department of Pediatrics, University of Geneva, Switzerland.

Abstract

Investigating context-dependent modulations of Functional Connectivity (FC) with functional magnetic resonance imaging is crucial to reveal the neurological underpinnings of cognitive processing. Most current analysis methods hypothesise sustained FC within the duration of a task, but this assumption has been shown too limiting by recent imaging studies. While several methods have been proposed to study functional dynamics during rest, task-based studies are yet to fully disentangle network modulations. Here, we propose a seed-based method to probe task-dependent modulations of brain activity by revealing Psychophysiological Interactions of Co-activation Patterns (PPI-CAPs). This point process-based approach temporally decomposes task-modulated connectivity into dynamic building blocks which cannot be captured by current methods, such as PPI or Dynamic Causal Modelling. Additionally, it identifies the occurrence of co-activation patterns at single frame resolution as opposed to window-based methods. In a naturalistic setting where participants watched a TV program, we retrieved several patterns of co-activation with a posterior cingulate cortex seed whose occurrence rates and polarity varied depending on the context; on the seed activity; or on an interaction between the two. Moreover, our method exposed the consistency in effective connectivity patterns across subjects and time, allowing us to uncover links between PPI-CAPs and specific stimuli contained in the video. Our study reveals that explicitly tracking connectivity pattern transients is paramount to advance our understanding of how different brain areas dynamically communicate when presented with a set of cues.

KEYWORDS:

Co-activation patterns (CAPs); Dynamic functional connectivity (dFC); Framewise analysis; PPI-CAPs; Psychophysiological interaction (PPI); Task fMRI

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