From Haziness to Clarity: A Novel Iterative Memory-Retrospective Emergence Model for Omnidirectional Image Saliency Prediction

To achieve saliency prediction in omnidirectional images (ODIs), the majority of prior works typically adopt the convolutional neural networks (CNNs)-based saliency models to extract semantic features to predict prominent regions in ODIs. Albeit achieving substantially performance gains, these works all employed purely visual computing paradigms and ignore to explore the nature of human visual attention mechanisms. In other words, existing saliency prediction works for ODIs are insufficient to capture the biological characteristics of the visual attention mechanism in the human brain. To establish a more explicit link between saliency prediction performance and brain-like visual attention mechanism, we simulate the mechanism of human retrospective memory in neuropsychology and propose IMRE model, a novel iterative memory-retrospective emergence model can predict and infer the salient features by recalling previously learned information. In IMRE model, we introduce four key modules to simulate the visual attention mechanism for predicting human fixations in the human brain. Firstly, the visual stimulus response module is designed to effectively extract semantic features and capture the intricate relationship between these features, acting as the human visual cortex. Secondly, the retrospective integration module serves to distill valuable information from a fuzzy memory ensemble, resembling the role of the basal ganglia in the neural system. Thirdly, the memory bank module explicitly records and stores subconscious response information and learned knowledge, acting like the hippocampus in neural system. Lastly, the prospective inference module accurately infers saliency maps from the refined useful information, resembling the role of the prefrontal cortex. During prediction, we utilize the introduced memory bank to retrieve and recall previously learned information, which simulates the process of memory emergence from haziness to clarity. Such a process aligns with the retrospective memory mechanism of the human brain. To validate the superiority of the proposed model in ODIs saliency prediction tasks, we conduct extensive experiments on two benchmark datasets. Experiments show impressive performances that IMRE model outperforms other state-of-the-art methods across all benchmark datasets. Importantly, experiments also highlight the IMRE model's ability to trace back to specific instances during prediction, thereby reducing model inference costs and enhancing interpretability.