Fig. 1: Gene expression predicts the location of tissue samples along the long axis of the hippocampus.

a (top) A curved skeleton of voxels was fitted along the center of mass of the hippocampal volume. (middle) Tissue samples (orange) were matched to the closest skeleton voxels (blue). (bottom) A sample's position along the longitudinal axis was represented as the y-axis coordinate of the sample's matched skeleton-voxel. b Average predicted sample position (using gene expression) across ten separate 10-fold cross-validated LASSO-PCR models, compared to the actual position. c Render of the hippocampal surface where each vertex shows the predicted location of the closest (surface projected) sample to that vertex. The smooth appearance of the right hippocampus is related to the fact that less samples were available for this structure. d Predicted vs. observed sample locations for leave-one-subfield-out models. For example, subpanel CA1 shows the predicted vs. observed position of samples extracted from CA1 (test set) when the model was trained without CA1 samples (training set). In each plot, N represents the number of samples in the training and test sets. e Predicted vs. observed sample locations for leave-one-donor-out models. f The 100 most important probes in the LASSO-PCR model were iteratively removed and, after each removal, 10-fold cross-validation accuracy predicting sample position along the longitudinal axis was recorded (blue dots). As a control, the same process was repeated but removing 100 random probes (orange). g The first 50 rounds of 100-probe removal from Panel F. Inflection points were identified after removing 100, 600, and 2700 genes. h Accuracy in predicting sample position was recorded for models using different gene sets identified by the inflection points in panel G (blue), samples of 100 random within-set probes (green), and samples of random probes (orange) as input. Each model was run ten times with different bootstrap samples to calculate confidence intervals (represented by error bars).