A poke, a pat, a nudge, and a stroke may seem like similar forms of touch, but the brain does not seem to perceive them the same way. Recent studies of a patient with a unique disability show that the differences may be hardwired into the body. One sensation—a soft caress—is processed by a set of nerves totally separate from those that mediate all other types of touch.
Neuroscientist Håkan Olausson of Sahlgrenska University Hospital in Göteborg, Sweden, made this discovery while examining a patient whose rare autoimmune disease left her with minimal bodily sensation below the nose. Although she could still feel heat, cold, and pain, she had lost her sense of touch and could no longer perceive the angle of her limbs. Doctors discovered that the disease had destroyed the patient's fast-conducting neurons, which had been thought to transmit all forms of touch to the brain, leaving only ...
