The patient lies on the operating table, with the right side of his body raised slightly. The anaesthetist sterilizes his scalp and injects it with Nupercaine to produce analgesia – the patient will remain fully conscious throughout the procedure. Behind the surgical drapes, three large incisions are made in his scalp. A large flap of bone is then cut from his skull, and turned downward to expose the surface of his brain. The ultraviolet lights which illuminate the operating theatre and keep the air sterile are positioned in such a way that they do not shine directly upon the cortex.
Using an atomizer, the surgeon sprays a small amount of Ringer’s solution onto the brain substance, to keep it moist. He then manoeuvres an electrode attached to a special holder which is clamped to the margin of the opening in the skull, so that it comes into direct contact with the brain. He adjusts a dial on the stimulator to 0.5 volts, and a current with a frequency of 60 cycles per second is applied to the patient’s cortex. After asking the patient if he feels anything, and getting a negative response, the surgeon reaches for the stimulator again. He turns the voltage dial up a notch so that it reads 1 volt, and applies another current. This time, the patient reports a tingling sensation in his face and, when asked to indicate exactly where, raises an arm and points to his left cheek and temple.