| Title:
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How to Define Amygdala as a Region of Interest in fMRI Studies: Evaluation of the Current Atlases and Their Variations
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| Author(s):
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1
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| Subject:
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Advanced Techniques in Signal Acquisition and Image Processing
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Presenter Author:
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| Name:
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Maryam Ardeshir
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Author:
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| Name 1:
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Maryam Ardeshir - Presenter
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| Affiliation 1:
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Iranian National Center for Addiction Studies
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| Name 2:
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Mohamad Bagher Soleimani
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| Affiliation 2:
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Iranian National Center for Addiction Studies
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| Name 3:
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Katayoun Nikimaleki
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| Affiliation 3:
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Iranian National Center for Addiction Studies
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| Name 4:
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Mehran Zare-Bidoky
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| Affiliation 4:
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Iranian National Center for Addiction Studies
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| Name 5:
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Hamed Ekhtiari - Corresponding
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| Affiliation 5:
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Laureate Institute for Brain Research, Tulsa, Oklahoma, USA
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| Name 9:
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Abstract
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Original Research
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introduction :
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The amygdala plays a pivotal role in emotional processing and cognition. Consistent and reliable localization of the amygdala is essential in functional magnetic resonance imaging (fMRI) research. In this review, we examined how recent human fMRI research defines and localizes the amygdala and its subregions.
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Methods:
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Following the PRISMA guidelines, we conducted a comprehensive search of the PubMed database targeting human fMRI studies published between January and December 2024 in which the amygdala was designated as a region of interest.
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Results:
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Of 178 retrieved records, 164 studies met the inclusion criteria. The Automated Anatomical Labeling (AAL) (n = 37), Harvard-Oxford (n = 34), Juelich (JuBrain Cytoarchitectonic Atlas) (n = 10), and Brainnetome (n = 8) atlases were the most frequently used atlases, respectively. Other methods of defining the amygdala among the retrieved studies included: FreeSurfer-based segmentation (n = 11), using custom and creating ROIs from prior literature (n = 12), Neurosynth meta-analytic tools (n = 7), and other specific atlases, such as the Melbourne Children’s Atlas, Chakravarty Atlas, and Geodesic Information Flows via NiftyWeb.
Among the majority of commonly used atlases, the right amygdala had a greater volume than the left. Across the Brainnetome, Harvard-Oxford, and AAL atlases, the right amygdala volumes were 2.75 cm³, 2.24 cm³, and 1.98 cm³, respectively, compared with left amygdala volumes of 2.49 cm³, 1.92 cm³, and 1.76 cm³. In contrast, the left amygdala volume was larger than the right in the Juelich atlas, measuring 3.43 cm³ on the left and 3.31 cm³ on the right. This difference was primarily due to the superficial subregion. Despite its larger size, the right amygdala showed a smaller overlap across atlases of 0.67 cm³, compared with 0.82 cm³ for the left amygdala.
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Conclusion:
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The AAL, Harvard-Oxford, Juelich, and Brainnetome atlases were the most commonly used tools for defining the amygdala in recent fMRI studies. The defined amygdala had different sizes and locations among various localization methods. Therefore, the research question and analytical framework should be considered when selecting a tool. Based on our findings regarding spatial asymmetry, analyzing the hemispheres separately and using multi-atlas approaches may improve robustness. Clear and standardized reporting of the amygdala ROI definitions in studies can improve reproducibility and interpretability in amygdala-focused fMRI research.
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| Attachment:
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| Keywords:
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Amygdala, functional neuroimaging, brain mapping.
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| Key message:
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