Abstract: Synesthesia is the simultaneous perception of different senses. There are strong synesthesia and weak synesthesia, with the former referring to explicit consciousness of a second sense perception and the latter to implicit feelings evoked by word descriptions of cross-modal sensories. Previous studies have found different types of strong synesthesia and provided evidence for many of these types by presenting various related activated brain areas. Reserachers attemped to explain the brain mechanisms of strong synesthesia by suggesting several corresponding theorietical models from the perspectives of either brain structure or cognitive processing. Furthermore, this article also reviewed the relationship between strong synesthesia and other cognitive processes (e.g., attention, memory, creation), discussed the current research status about weak synesthesia, and suggested the future research trend in synesthesia.

Key words: (strong/weak)synesthesia, synesthetic models, synesthetic metaphor