Effects of different smoothing on global and regional resting functional connectivity
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FUNCTIONAL NEURORADIOLOGY
Effects of different smoothing on global and regional resting functional connectivity Adnan A. S. Alahmadi 1 Received: 2 July 2020 / Accepted: 13 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose Spatial smoothing is an essential pre-processing step in the process of analysing functional magnetic resonance imaging (fMRI) data, both during an experimental task or during resting-state fMRI (rsfMRI). The main benefit of this spatial smoothing step is to artificially increase the signal-to-noise ratio of the fMRI signal. Previous fMRI studies have investigated the impact of spatial smoothing on task fMRI data, while rsfMRI studies usually apply the same analytical process used for the task data. However, this study investigates changes in different rsfMRI analyses, such as ROI-to-ROI, seed-to-voxels and ICA analyses. Methods Nineteen healthy volunteers were scanned using rsfMRI with three applied smoothing kernels: 0 mm, 4 mm and 8 mm. Appropriate statistical comparisons were made. Results The findings showed that spatial smoothing has a greater effect on rsfMRI data when analysed using seed-to-voxel-based analysis. The effect was less pronounced when analysing data using ROI-ROI or ICA analyses. The results demonstrated that even when analysing the data without the application of spatial smoothing, the results were significant compared with data analysed using a typical smoothing kernel. However, data analysed with lower-smoothing kernels produced greater negative correlations, particularly with the ICA analysis. Conclusion The results suggest that a medium smoothing kernel (around 4 mm) may be preferable, as it is comparable with the 8 mm kernel in all of the analyses performed. It is also recommended that the researchers consider analysing the data using two different smoothing kernels, as this will help to confirm the significance of the results and avoid overestimating the findings. Keywords fMRI . Functional connectivity . Spatial smoothing
Background Functional magnetic resonance imaging (fMRI) is a noninvasive technique that is used to investigate functional localisation and integrations. Functional localisation refers to localising brain activity during a certain task, such as finger tapping which would produce signals in the regions of the brain that control the tapping of a finger (i.e. the motor cortex). Functional integrations refer to the investigation of regional brain networks during a task or during rest periods [1]. During rest, subjects are not performing any type of task, and an examination of the functional connectivity could therefore
* Adnan A. S. Alahmadi [email protected]; [email protected] 1
Department of Radiologic Sciences, College of Applied Medical Science, King Abdulaziz University (KAU), Jeddah, Saudi Arabia
be tested using resting-state fMRI (rsfMRI) [2]. fMRI is a powerful tool that can assist in investigating and understanding physiological behaviours and changes in people or animals, as well as obse
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