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The Effects of Amygdalar Size Normalization on Group Analysis in Late-Life Depression

Tamburo, Robert and Becker, James and Siegle, Greg and Butters, Meryl and Reynolds, Charles and Aizenstein, Howard J (2012) The Effects of Amygdalar Size Normalization on Group Analysis in Late-Life Depression. Technical Report. UNSPECIFIED. (Unpublished)

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Structural MRI has been utilized in numerous ways to measure morphologic characteristics of subcortical brain regions. Volumetric analysis is frequently used to quantify the size of brain structures to ultimately compare size differences between individuals. In order to make such comparisons, inter-subject variability in brain and/or head size must be taken into consideration. A heterogeneous set of methods are commonly used to normalize regional volume by brain and/or head size yielding inconsistent findings making it diffcult to interpret and compare results from published volumetric studies. This study investigated the effect that various volume normalization methodologies might have on group analysis. Specifically, the amygdalae were the regions of interest in elderly, healthy and depressed individuals. Normalization methods investigated included spatial transformations, brain and head volume, and tissue volume techniques. Group analyses were conducted with independent t-tests by dividing amygdalar volumes by various volume measures, as well as with univariate analysis of covariance (ANCOVA) analyses by using amygdalar volumes as dependent variables and various volume measures as covariates. Repeated measures ANOVA was performed to assess the effect of each normalization procedure. Results indicate that volumetric differences between groups varied based on the normalization method utilized, which may explain, in part, the discrepancy found in amygdalar volumetric studies. We believe the findings of this study are extensible to other brain regions and demographics, and thus, investigators should carefully consider the normalization methods utilized in volumetric studies to properly interpret the results and conclusions.


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Item Type: Monograph (Technical Report)
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Tamburo, Robert
Becker, JamesBECKERJT@pitt.eduBECKERJT
Siegle, Greg
Butters, Merylmerylb@pitt.eduMERYLB
Reynolds, Charleschipr@pitt.eduCHIPR
Aizenstein, Howard Jaizen@pitt.eduAIZEN
Centers: Other Centers, Institutes, Offices, or Units > Alzheimer's Disease Research Center
Other Centers, Institutes, Offices, or Units > Center for Neuroscience
Other Centers, Institutes, Offices, or Units > Center for the Neural Basis of Cognition
Monograph Type: Technical Report
Date: 1 March 2012
Date Type: Publication
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Clinical Research
Refereed: Yes
Uncontrolled Keywords: Amygdala, morphometry, depression, structural, MRI
Date Deposited: 05 Mar 2012 20:28
Last Modified: 11 Jan 2021 11:55


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