Continual test-time domain adaptation (CTTA) aims to adapt a pre-trained source model to a stream of continually evolving unlabeled target domains, facilitating model deployment in dynamic and non-stationary environments. Contemporary works usually encode domain-specific (DS) style information in a domain-agnostic manner, synchronizing with the learning of domain-invariant (DI) semantic information. This scheme forces DS information to be optimized using the weights of the previous domain, corrupted by cross-domain discrepancies, and hence leads to error accumulation and catastrophic forgetting issues. Inspired by the Attribute Memory Model (AMM) in brain neuroscience, we propose a dual domain-attribute learning framework based on independent asynchronous updates, aiming to imitate how brain learns new knowledge without forgetting. Concretely, we explicitly decompose the continual adaptation process into two complementary systems: an event-based learning system (ELS) that captures DS style representations and a knowledge-based learning system (KLS) that concentrates on the DI structural characteristics. The ELS first detects differences in the distribution of data streams, and actively builds an adapter pool for new latent domains. The KLS adopts a cross-domain shared adapter emphasizing general knowledge, and cooperates with the adapter from ELS to jointly guide adaptation. To make DS and DI knowledge collaboratively working, we exploit a gradient conflict solver to ease the conflict between the past and current DI knowledge, realizing a win-win game (i.e., no interference adaptation) across evolving domains. Our framework have been extensively evaluated on four benchmarks and outperformed the state-of-the-art approaches on both segmentation and classification CTTA tasks.

This paper studies a practical Source-free unsupervised domain adaptation (SFUDA) problem, which transfers knowledge of source-trained models to the target domain, without accessing the source data. It has received increasing attention in recent years, while the prior arts focus on designing adaptation strategies, ignoring that different target samples exhibit different transfer abilities on the source model. Additionally, we observe pixel-wise class prediction is typically accompanied by ambiguity issue, i.e., prediction errors often occur between several confusing classes. In this study, we propose a dual-branch collaborative learning framework that aims to achieve reliable knowledge transfer from important samples to the rest by fully mining confident prototypes in the target data. Concretely, we first partition the target data into confident samples and uncertain samples via a new class-ranking reliability score and then utilize the latent features from the confident branch as guidance to promote the learning of the uncertain branch. For ambiguity issue, we propose a feature relabelling module, which exploits reliable prototypes in the mini-batch as well as in the target data to refine labels of uncertain features. We further deploy the proposed framework to commonly used CNN and state-of-the-art Transformer architectures and reveal the potential to promote the generalization ability of backbone models. Experimental results on both natural and medical benchmark datasets verify that our proposed approach exceeds state-of-the-art SFUDA methods with large margins, and achieves comparable performance to existing UDA methods.