Coupling Semi-supervised Learning with Reinforcement Learning for Better Decision Making --- An application to Cryo-EM Data Collection

We consider a semi-supervised Reinforcement Learning (RL) approach that takes inputs from a perception model. Performance of such an approach can be significantly limited by the quality of the perception model in the low labeled data regime. We propose a novel iterative framework that simultaneously couples and improves the training of both RL and the perception model. The perception model takes pseudo labels generated from the trajectories of a trained RL agent believing that the decision-model can correct errors made by the perception model. We apply the framework to cryo-electron microscopy (cryo-EM) data collection, whose goal is to find as many high-quality micrographs taken by cryo-electron microscopy as possible by navigating at different magnification levels. Our proposed method significantly outperforms various baseline methods in terms of both RL rewards and the accuracy of the perception model. We further provide some theoretical insights into the benefits of coupling the decision model and the perception model by showing that RL-generated pseudo labels are biased towards localization which aligns with the underlying data generating mechanism. Our iterative framework that couples both sides of the semi-supervised RL can be applied to a wide range of sequential decision-making tasks when the labeled data is limited.