Neuroanatomical bases for synesthesia and their implications for perception and consciousness

Synesthesia is a condition that affects an individual’s conscious perception of the world. Individuals with this disorder vary greatly, but have in common the phenomenon of cross-modal perceptions. For example, grapheme-color synesthetes perceive color when presented with graphemes, such as letters and numbers. In this review, we investigate this phenomenon further in order to evaluate the plausibility of currently proposed mechanisms. There is some debate about whether synesthetic mechanisms are primarily perceptual or are primarily concept-driven. There are also important questions about the relationship of attention and consciousness to synesthesia, and here we examine specific studies that shed light on this issue. We will show that the evidence suggests a wide heterogeneity between synesthetic subjects. We will also demonstrate that both perceptual and concept driven hypotheses are crucial to the understanding of the inner neural mechanisms of synesthesia. By achieving said understanding, we may be able to gain valuable information about how conscious experience is produced through neural