Psychophysiological Interactions in a Visual Checkerboard Task: Reproducibility, Reliability, and the Effects of...

Area of Science:

• Neuroimaging
• Cognitive Neuroscience
• Functional Magnetic Resonance Imaging (fMRI)

Background:

• Psychophysiological interaction (PPI) is a widely used fMRI method to assess task-modulated functional connectivity.
• The reliability and reproducibility of PPI findings, crucial for robust scientific conclusions, have remained largely unevaluated.

Purpose of the Study:

• To investigate the reproducibility and reliability of PPI effects in a simple visual task.
• To examine the impact of deconvolution preprocessing on PPI results.
• To assess the consistency of PPI findings across different repetition times (TRs) and analysis methods.

Main Methods:

• Analysis of a large open-access fMRI dataset (n=138) with a visual task scanned twice using TRs of 645 ms and 1,400 ms.
• Seed-based and region of interest (ROI)-wise analyses were conducted on 20 visual-related thalamic and cortical regions.
• Comparison of PPI results with and without deconvolution, and across different TRs.

Main Results:

• PPI analysis demonstrated good reproducibility between runs and similarity between deconvolution and non-deconvolution methods.
• Negative PPI effects were observed, with the posterior fusiform gyrus acting as a hub.
• Non-deconvolution and shorter TR (645 ms) generally yielded larger effect sizes, though deconvolution performed less optimally with the shorter TR.
• Intraclass correlations (ICC) for PPI effects were notably lower than for main activation effects between runs.

Conclusions:

• Deconvolution may not be essential for PPI analysis in block-designed fMRI studies, given the comparable results and uncertainties associated with its application.
• The lower reliability of PPI effects compared to activation main effects necessitates caution when performing inter-subject correlations and group comparisons.
• Findings highlight the importance of rigorous validation for connectivity measures in neuroimaging research.