Going Beyond Saliency Maps: Training Deep Models to Interpret Deep Models

TL;DR

This paper introduces a novel interpretability method for deep learning models in neuroimaging, using simulator networks to visualize disease-related brain patterns beyond traditional saliency maps.

Contribution

It proposes a new approach employing simulator networks and image warping to generate human-understandable visualizations of disease effects in brain images.

Findings

Simulations reveal meaningful disease-related patterns.

Method outperforms saliency maps in interpretability.

Effective on both synthetic and real neuroimaging data.

Abstract

Interpretability is a critical factor in applying complex deep learning models to advance the understanding of brain disorders in neuroimaging studies. To interpret the decision process of a trained classifier, existing techniques typically rely on saliency maps to quantify the voxel-wise or feature-level importance for classification through partial derivatives. Despite providing some level of localization, these maps are not human-understandable from the neuroscience perspective as they do not inform the specific meaning of the alteration linked to the brain disorder. Inspired by the image-to-image translation scheme, we propose to train simulator networks that can warp a given image to inject or remove patterns of the disease. These networks are trained such that the classifier produces consistently increased or decreased prediction logits for the simulated images. Moreover, we propose to couple all the simulators into a unified model based on conditional convolution. We applied our approach to interpreting classifiers trained on a synthetic dataset and two neuroimaging datasets to visualize the effect of the Alzheimer's disease and alcohol use disorder. Compared to the saliency maps generated by baseline approaches, our simulations and visualizations based on the Jacobian determinants of the warping field reveal meaningful and understandable patterns related to the diseases.