Large Language Models (LLMs) have shown great potential in the biomedical domain with the advancement of retrieval-augmented generation (RAG). However, existing retrieval-augmented approaches face challenges in addressing diverse queries and documents, particularly for medical knowledge queries, resulting in sub-optimal performance. To address these limitations, we propose a novel plug-and-play LLM-based retrieval method called Self-Rewarding Tree Search (SeRTS) based on Monte Carlo Tree Search (MCTS) and a self-rewarding paradigm. By combining the reasoning capabilities of LLMs with the effectiveness of tree search, SeRTS boosts the zero-shot performance of retrieving high-quality and informative results for RAG. We further enhance retrieval performance by fine-tuning LLMs with Proximal Policy Optimization (PPO) objectives using the trajectories collected by SeRTS as feedback. Controlled experiments using the BioASQ-QA dataset with GPT-3.5-Turbo and LLama2-7b demonstrate that our method significantly improves the performance of the BM25 retriever and surpasses the strong baseline of self-reflection in both efficiency and scalability. Moreover, SeRTS generates higher-quality feedback for PPO training than self-reflection. Our proposed method effectively adapts LLMs to document retrieval tasks, enhancing their ability to retrieve highly relevant documents for RAG in the context of medical knowledge queries. This work presents a significant step forward in leveraging LLMs for accurate and comprehensive biomedical question answering.

Despite the popularity of Large Language Models (LLMs), crafting specific prompts for LLMs to perform particular tasks remains challenging. Users often engage in multiple conversational turns with an LLM-based agent to accomplish their intended task. Recent studies have demonstrated that linguistic feedback, in the form of self-reflections generated by the model, can work as reinforcement during these conversations, thus enabling quicker convergence to the desired outcome. Motivated by these findings, we introduce METAREFLECTION, a novel technique that learns general prompt instructions for a specific domain from individual self-reflections gathered during a training phase. We evaluate our technique in two domains: Infrastructure as Code (IAC) vulnerability detection and question-answering (QA) using REACT and COT. Our results demonstrate a notable improvement, with METARELECTION outperforming GPT-4 by 16.82% (IAC), 31.33% (COT), and 15.42% (REACT), underscoring the potential of METAREFLECTION as a viable method for enhancing the efficiency of LLMs.