Synaesthesia: The existing state of affairs

Abstract

In synaesthesia one type of stimulation evokes the sensation of another, such as when hearing a sound produces photisms--that is, mental percepts of colours. In the past, the idiosyncrasy of this phenomenon, as well as the natural mistrust of scientists towards the subjective, consigned synaesthesia to the periphery of scientific interest. However, the landscape has changed radically in the last two decades. The labour of many researchers, inside as well as outside of cognitive neuroscience, has transformed synaesthesia into a scientific reality whose existence can be demonstrated and studied empirically. The present paper summarizes and reflects on our current knowledge concerning synaesthesia in all its aspects (cognition, behaviour, neurology, genetics, and demographics).

Exceptional Abilities in the Spatial Representation of Numbers and Time

“…Synesthesia is not restricted to TNS and is present for a wide variety of psychological processes (e.g., listening to music, seeing a grapheme) that automatically trigger ancillary, exceptional experiences (e.g., color, taste, smells, pain) in the absence of any direct stimulation pertaining to the secondary experience Cytowic and Eagleman 2009;Hochel and Milan 2008;Hubbard and Ramachandran 2005;Rich and Mattingley 2002;Robertson 2003;Robertson and Sagiv 2004;Ward and Mattingley 2006). For example, for some people who see digits in colors (termed digit-color synesthesia), an achromatic 7 will appear in a distinct color such as turquoise .…”

Effective Connectivity Determines the Nature of Subjective Experience in Grapheme-Color Synesthesia

“…We focused on grapheme-color synesthesia, where synesthetes perceive a color induced by written letters and/or digits (e.g., black letter "J" elicits orange). These idiosyncratic synesthetic colors appear automatically and remain stable during life (Hochel and Milán, 2008). During grapheme-color synesthesia, brain activity is enhanced in both color area V4 and the superior parietal lobe (SPL) Weiss et al, 2005;Sperling et al, 2006;van Leeuwen et al, 2010), an area involved in multimodal integration (Robertson, 2003).…”

“…In synesthesia, specific sensory stimuli lead to unusual additional experiences (Hochel and Milán, 2008). We focused on grapheme-color synesthesia, where synesthetes perceive a color induced by written letters and/or digits (e.g., black letter "J" elicits orange).…”

As bitter as a trombone: Synesthetic correspondences in nonsynesthetes between tastes/flavors and musical notes

“…Although the first detailed scientific report on synesthesia dates from more than a century ago (Galton, 1880), its mechanisms are still unclear (Cytowic & Eagleman, 2009). More attention has been devoted by researchers recently to various cases of synesthesia (see Hochel & Milán, 2008, for a review; see also Harrison, 2001). But are the perceptual experiences of synesthetes so very different from those of nonsynesthetes?…”