This edition of The Man Who
Tasted Shapes is a republication of Cytowic’s 1993 book, with the addition
of a new afterword.  The author notes in the chapter on Foreword to the MIT
Edition that " Since the publication in 1989 of the textbook Synesthesia:
A Union of the Senses [reviewed in Metapsychology
6:42], the first English-Language book devoted to the phenomenon, and
The Man Who Tasted Shapes in 1993, there has been a renaissance of interest in synesthesia
as neuroscience has relaxed its reflexive hostility to subjective experience.
Today, researchers in some fifteen countries are studying it, and many doctoral
candidates have chosen synesthesia for their theses" p. 231.

Employing
a medical mystery narration of two synesthetes of Watson’s and Victoria’s in
Part One of the book in 21 chapters, the author, begins informing the readers
about synesthesia. Along with all this, Cytowic’s thought processes, hunches,
and the author’s persistence in uncovering the story and the conditions he
passed through over a period of a decade or so, and others’ indifference and
hostility encountered while pursuing this subject are also revealed.

The
word synesthesia, meaning "joined sensation", shares a root with anesthesia, meaning "no
sensation." It denotes the rare capacity to hear colors, taste shapes, or
experience other equally startling sensory blendings whose quality seems
difficult for most of us to imagine. A synesthete might describe the color,
shape, and flavor of someone’s voice, or music whose sound looks like
"shards of glass," a scintillation of jagged, colored triangles
moving in the visual field. Or, seeing the color red, a synesthete might detect
the "scent" of red as well. The experience is frequently projected
outside the individual, rather than being an image in the mind’s eye. It
conjures up other senses, sometimes all the five clashing together (Cytowic, 1993).
There are altered states of consciousness that bear similarity to synesthesia.
These being: (1) LSD- induced synesthesia, (2) Photographic memory, (3) Sensory
deprivation, (4) temporal lobe epilepsy, (5) release hallucination, and (6)
direct stimulation of the brain cortex.

One of the foremost contemporary writers on synesthesia,
Richard E. Cytowic, has proposed a theory of its neural basis. The theory is
considered as "more scientific" that follows theories from physics
and neurological disorders, as well as the study of effects of psychoactive
drugs. Important to his work is his definition of the phenomenon, which is
comprised of several pieces, for example that synesthesia is:

·        
neither voluntary or controllable by the subject, or constant —
it is usually triggered by some stimulus

·        
"projected" — perceived to take place in the area
immediately surrounding the subject

·        
"durable and generic" — associations between the
senses will be constant over time and will also be relatively abstract

Cytowic’s surprising claim is
that synesthesia is not a result of cortical activity. This is in direct
opposition to theories of the brain basis for normal conscious
sensation. In general, most such theories assume not only a cortical substrate
per se, such as the primary sensory modalities, but also argue for the
necessary role of extensive processing in the frontal areas of the cortex.
Contrary to this, Cytowic cites several pieces of evidence that synesthesia is
accompanied by increased limbic activity — that is, activity in structures
"below" the cortex, often seen as more primitive structures, at the
same time, accompanied by a decrease in cortical activity.  (From an article by
Thomas Zoëga Ramsøy, Seeing Sounds and Hearing Tastes: Synesthesia in Brain and
Mind, Science and Consciousness Review, 1 (1), 2001.