Fig. 7: Comparative analyses confirming reproducible DL research on brain imaging data.

A comparative analysis with the simple fully convolutional network (SFCN) DL model and training pipeline used in Peng et al. (2020) and Schulz et al. (2020) confirmed similar performance levels as our DL models and training pipeline, thus providing a great insight into the reproducibility of these brain imaging research objectives with DL. Several pipelines that differed in the combination of the used DL model (“DL1”, “DL3”, or “SFCN”), training settings (for example, choice of optimizer, learning rate, early stopping parametrization, etc. highlighted as “Abrol” if using similar to our work, and as “Schulz” or “Schulz_C” if using similar to comparative work) and training code (labeled with the “@” superscript when implemented with our custom training code and the “*” symbol when using the PyTorch lightning trainer as in Schulz et al.). Note, “Schulz_C” denotes the case when the coding bug in this comparative work was corrected. Specifically, the distributions of the mean absolute error (MAE), Pearson correlation coefficient (r), and coefficient of determination (R2) metrics are compared for the age regression task (top row), and the distribution of classification accuracy is compared for the two classification tasks (bottom row). Each boxplot shows the discriminative performance on unseen test data for the cross-validation repetitions (n = 20) for the highest training sample size (ntrain = 10,000; nvalidation = 1157; ntest = 1157). The color scheme for the boxplots is arbitrary, whereas the circles on these boxplots indicate the performance for a given cross-validation repetition. The box in these boxplots shows the inter quartile range (IQR between Q1 and Q3) of the data set, the central mark shows the median and the whiskers correspond to the rest of the distribution based on the IQR [Q1–1.5*IQR, Q3+1.5*IQR]. Beyond the whiskers, data are considered outliers and represented by the diamond-shaped marker. Source data are provided as a Source Data file.