Susan is putting herself through this drastic operation for a very modest reason: she wants her old life back. Her symptoms have been controlled in recent years with a drug called apomorphine, involving the insertion every morning of a needle into her stomach controlled by a pump, which is cumbersome and often lets her down.
She is to receive two electrode implants deep in her brain, to be attached to wires that will run under her skin to a miniature battery-operated pulse generator that will be sewn into her chest. The electrodes will permanently stimulate cells deep in her brain to alleviate her symptoms. Amazingly, she will remain awake throughout the procedure: the best indication that things have not gone to plan — a haemorrhage, for example — is the patient's own report of symptoms. The operation will cost the NHS some £30,000. Her local authority, Berkshire, thinks the money well spent, as the apomorphine regime costs £10,000 each year. The electrodes will last her the rest of her life.
I am standing next to the surgeon, Professor Tipu Aziz. Originally from Bangladesh, he is one of the leading implantists in the world, having done more than a thousand such ops since 1991. He has quick, delicate fingers, a Sancho Panza moustache, and an idiosyncratic sense of humour. A Chemical Brothers track belts out from the CD player behind us ("I like this stuff when I go to work," he says). Leaning over his patient, he quips: "Brain surgery is such fun, isn't it!" From inside the head frame, which forms part of the system for a stereotactic contraption that guides the probe into her brain, Susan smiles wanly.
There are 10 attending medical staff: the theatre is tense. Brain surgery earned a bad name in the 1940s and 50s, when hundreds of thousands of patients underwent lobotomies for a wide range of conditions, from schizophrenia to depression. All too often the recipients became vegetables. But new implant technologies, matching human living tissue with intricate mechanical devices, have prompted a new era in psychosurgery.
The prospects, according to the implant practitioners and their advocates, are thrilling. But there are deep concerns. Are we on the brink of a new epoch of surveillance, mind control, and the melding of human and machine existence?
Like the biblical tree of good and evil, the quest for a bionic man has huge potential for human benefit as well as for ill. Researchers are set to create a new generation of prosthetic applications: making the deaf hear, the blind see, the dumb speak, the paralysed move. They are poised to conquer pain and treat illnesses like depression and Parkinson's. Beyond that lie once-unthinkable possibilities based on the interaction between minds and machines in the fields of military technology and surveillance. Millions of animals have already been implanted with "identity cards" the size of a grain of rice. How long before humans will be similarly tagged? Researchers are experimenting with implants that enable them to direct the movements of rats in inhospitable environments — like miniature St Bernard dogs. The same technique promises implants that control mechanical devices by the act of thinking alone. Most controversial of all — raising spectres familiar in the Johnny Mnemonic and Matrix movies — scientists believe there is potential for boosting brain power and controlling emotions.
Before he starts the operation, Aziz asks Susan to make leg, foot, arm and hand movements in order to demonstrate her tremors and rigidity. Administering a local anaesthetic into the scalp, Aziz uses a diathermic needle to make an incision in the flesh on the left side of her skull, above the temple, pinning back the small flap of scalp tissue in order to expose an area of bone. "I haven't shaved her head," he tells me. "I've given it a good antiseptic wash. I don't like to send my patients home looking as if they've had brain surgery." Everybody laughs, including Susan.
Next he puts the frame holding the stereotactic contraption in place and begins to drill into the bone. It is a hand drill, its head 2.7mm in diameter; she feels no pain, there is no noise, but she can feel the vibration. Now begins the trickiest part. Aziz inserts a tiny hollow probe, containing a lead with an electrode head, through the hole. He guides it with computer-assisted precision through about 18cm of brain matter, monitoring its progress with a machine that measures tissue resistance, until it reaches the sub-thalamic nucleus (a deep region of the brain connected with speech and movement). Now that Aziz has reached the optimal target, an assistant sends electrical impulses through the lead to the electrode head.
Parkinson's reduces the firing potential of neurones, or brain cells, in areas of the brain associated with limb and hand movement. The electrical stimulus from the implanted electrode gets the neurones firing once more in a regular pattern. Nicely oscillating nerve cells will then deliver appropriate "messages", composed of refined electrical discharges and associated natural chemicals, to their target regions.
Aziz says he has used the technique to alleviate intractable pain. "It's worked with stroke pain, cluster headaches and phantom limb, when people have an agonising sense of pain in an amputated extremity." The theory, he tells me, is the same. "Nervous pain is caused by a disturbance in the firing patterns following trauma, and the electrode implants reinstate and maintain virtually normal oscillations, reducing or expelling the pain."
He now asks Susan to exercise her right leg, which is controlled by the left brain. To the delight of everybody in the theatre she begins to make vigorous, well-controlled cycling movements with her leg followed by wide circular movements. She has not done this for years. Then she demonstrates an unaccustomed dexterity in her right arm and hand. "Oh wow!" says Aziz. "That's just amazing." Susan smiles weakly. Aziz prepares to treat the right side of her brain. By the time he finishes, Susan has been in surgery for nearly two hours.
The electrodes implanted into Susan's brain are made of platinum iridium, a soft but durable metal that looks rather like a silver strand of thin spaghetti. Essential to the task of hitting the right spot are new techniques of magnetic resonance imaging, which enable the investigator to explore the topography of an individual brain without devastating what they probe.
