Everyday fantasia: “With the help of sophisticated behavioral
brain-imaging and molecular genetic methods,
researchers are coming closer to
understanding what drives the extraordinary
sensory condition called synesthesia.” First psychologists showed that, in synaesthetes, the associations across sensory modalities are stable over time and involuntary (even when they interfere with normal perception), implying a fixed and automatic mechanism in their brains. fMRI studies showed that the cross-modality sensory areas were actually activated, as one would expect — for example, in a synaesthete who “sees” music s/he is hearing, the visual areas are active as well as the auditory.
In fact, it may be the concept, not the percept, that causes the sensory experience (for example, in one synaesthete tho experiences colors for numbers, presenting him with “5+2” causes him to experience the color associated with the concept “7”). This would turn on its head the usual “bottom-up” notion of sensory processing and would suggest that synaesthetes demonstrate a lack of the usual inhibition of “feed-backward” connections from high-level multisensory areas to single-sense cortical areas. Another theory suggests that synaesthetes’ brains may be richly crosswired with extra connections, perhaps a connectivity with which we are all endowed at birth but which normally devolves. This is not an alien concept; brain development is known in other regards to depend on the dying-off of neuronal connections as much as the elaboration of new ones over time. Any neurophysiological theory of synaesthesia would have to account for the fact that the phenomenon is temporarily induced by hallucinogenic drugs; it would be hard to imagine that the drug experience stimulates the rapid growth of new neuronal connections which then disappear after the drug is out of the user’s system.
Whatever theory is correct, an implication that occurs to me is that there is probably a continuum of synaesthetic experience from total absence to fullblown. While I’m certainly not a robust synaesthete, I suspect I have a degree of the overconnectivity, since I’ve always noticed I have vivid and enduring experiences of colors associated with various concepts — numbers, sounds, names of people and the days of the week. For example, “Monday” is a kind of lime green and “Thursday” a rose-tinged grey, and always has been — no, really! On the other hand (indulge me for a moment), these may not be neurophysiological correlations at all, but rather unconscious psychological ones — i.e. not classically-described synaesthesia at all. For example, while writing this paragraph, endeavoring to describe the color experience I have for “Friday,” I was just now surprised to find that what first came to mind was the phrase “fried-egg-yolk yellow.” It immediately made me wonder if the connection is the sound-association between “Friday” and “fried”, not a cross-modality experience at all. In other words, “Friday” may be that shade of yellow because it reminds me of “fried egg.” There may be similar associative reasons for the other color experiences that are there despite remaining opaque to me so far. Oh, well.
In any case, interesting to me in my professional work, where I focus on the phenomenology of psychotic symptoms, is the suggestion by some researchers that synaesthesia may share some neurobiological similarity with hallucinations. Could schizophrenics think thery’re hearing voices talking to them because they’re, unbeknownst to themselves, experiencing “crosstalk” from a sensory experience in a disparate modality such as taste or vision? This does not at all square with my own theory of hallucinatory experience, but it’s intriguing nonetheless, although difficult to study both because its experiencers are in distress to an extent that would make it hard for them to cooperate with neurophysiological investigation; and because most actively psychotic patients accessible to study are medicated (and it would be unethical not to medicate them, IMHO!).
One curiosity I’ve always had about synaesthesia is if the “crossed” sensory modalities ever include the kinesthetic sense. Often considered our “sixth sense”, this is our visceral body experience — i.e. our perception of the position, extent, and movement of our body parts in space. Are there synaesthetes who, for example, experience a sound or a color when they swing their arm around, take a step, open their mouth? How about the reverse — experiencing movement in or change of position of a body part as part of the perception of a sound or a shape? [Could this relate to the visceral component of aesthetic experience? (Benjamin Whorf: “Probably in the first instance metaphor arises from synesthesia and not the reverse.”)]
A number of fascinating hits emerge from a Google search on “(synesthesia OR synaesthesia) AND (kinesthesia OR kinaesthesia)”, including this collection of interesting analyses of Beatles music.
