Computational protocol: Physical activity reduces hippocampal atrophy in elders at genetic risk for Alzheimer's disease

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Protocol publication

[…] The hippocampus was selected a priori as the key structure for examining the longitudinal volumetric effects of PA. In addition, we measured changes in volumes of the thalamus, caudate, amygdala, caudal middle frontal gyrus, pre-central gyrus, total gray matter (GM), and cortical white matter (WM) to determine if PA effects were specific to the hippocampus. Volumetric measurements were obtained from parcellation of anatomical T1 images at baseline and at 18-months using the longitudinal method of FreeSurfer software (v. 5.1) (Fischl et al., ). The first stage consisted of identifying the GM/WM boundary (Dale et al., ) using both intensity and continuity information from the entire 3D volume. Maps were then created using spatial intensity gradients across tissue classes. Using an automated labeling system, GM and WM were subdivided into distinct volumes of interest per hemisphere (Desikan et al., ). Homologous left and right hemisphere volumes were summed, as these volumes were highly correlated and we did not have a hypothesis regarding hemispheric differences. In addition, total intracranial volume (ICV) was calculated to account for inter-individual differences in head size. Each volume of interest was expressed as a percentage of total ICV (%ICV). Change in volume was achieved by subtracting baseline and follow-up %ICV and then expressed as a percent change from baseline. This change score was subjected to a 2 (High Risk vs. Low Risk) × 2 (High PA vs. Low PA) analysis of variance (ANOVA; SPSS 21, Chicago, IL). Significant effects were followed by post-hoc group comparisons. […]

Pipeline specifications

Software tools FreeSurfer, SPSS
Application Miscellaneous
Organisms Homo sapiens
Diseases Alzheimer Disease, Leukoencephalopathies