Mechanisms of synesthesia: cognitive and physiological constraints

Synesthesia is a conscious experience of systematically induced sensory att ributes that are not experienced by most people under comparable conditions . Recent findings from cognitive psychology, functional brain imaging and p sychophysiology have shed considerable light on the nature of synesthesia a nd its neurocognitive underpinnings. These cognitive and physiological find ings are discussed with respect to a neuroanatomical framework consisting o f hierarchically organized cortical sensory pathways. We advance a neurobio logical theory of synesthesia that fits within this neuroanatomical framewo rk.