When the senses become confused – Synesthesia
Imagine being able to feel sound – really feel it. That is exactly what happened to one young woman after having a stroke. Sandra Blakeslee reports in the New York Times that Sherrilyn Roush suffered from a midbrain stroke, and a year and a half later began feeling tingling on her body in response to sounds.
This odd mixing of the senses, synesthesia, occurs when sensory areas of the brain that do not normally communicate engage in cross-talk. Most synesthetes are born with crossed connections, it manifests itself in different ways, some can “taste” words, others may feel complex shapes in response to taste, or even see colors attached to specific letters or numbers.
In this case, Dr. Ro said, the crossed wiring developed as a consequence of the stroke. Imaging studies reveal that fiber tracts from Dr. Roush’s midbrain that normally go to higher regions involved in touch are disorganized and diminished. Such disruption can lead to enhanced connectivity in remotely connected regions of the brain like hearing and touch.
Dr. Ro and colleagues have tested Dr. Roush for the last seven years, observing how her brain has reorganized. An article describing her case appears in the November issue of Annals of Neurology.
For several months, Dr. Roush found herself bumping into doors. When she drove, her car would veer to the right. But gradually, the weakness on her left side and the neglect of space around her left side diminished. Her only concession was to give up driving a car with a stick shift because of lingering weakness in her leg.
But in laboratory tests a year later, she exhibited a rare phenomenon. If simultaneously touched on both hands, she would feel an increased sense of pressure on her left hand. Her brain was reorganizing in ways that baffled her doctors.
Not long after that, sounds began to produce tingling, hair-raising sensations of touch on her body. Something about that radio announcer’s voice — its pitch or timbre — was unbearably irritating. The sound of a duck quacking or the sharp clanging of a fire alarm sets her teeth on edge. When she rides the subway, the sound of the train hitting the rails makes her left side “feel on the way to tingle.”
But the soft sound of water bubbling is “soothing, almost like a massage on my skin,” Dr. Roush said, adding, “Round sounds produce a very light tickle but without the annoying part of being tickled.”
She always feels touch sensations, positive and negative, on the left side of her body, particularly the outside of her arm, thigh, head and shoulder. They do not reach the bottom of her leg. Sometimes they make her squirm. But most, she said, do not interfere with everyday life.