The bespectacled skeleton speaks. "Yes, I'm fine," she says. Her jaw drops and rises squarely like a ventriloquist's dummy. But where are the words coming from? All I can see are bones and electrodes. The view shifts and there's the smoky shape of the heart. The tip of the catheter now appears at the bottom of the screen. This was inserted at the groin and is nudging upward, through an invisible artery, into the rib cage. The radiologist is deft and reaches the carotid in no time: base camp for the brain. He is ready now to squirt the drug into the cerebral blood vessels. Next scene: the inside of Julie's head. There is nothing much to see.
Julie has temporal lobe epilepsy. Although her condition is unresponsive to medication, a small, well defined area of abnormal brain tissue has been identified as the source of the seizures, and can be surgically excised. She's already been through an assault course of clinical investigations and her doctors know that the scar tissue driving the fits is on the left side of the brain. But to get on the surgeon's list she must, finally, pass the bizarre test we are about to witness: the Wada procedure. A fast-acting sedative will be injected into her brain, suppressing each hemisphere in turn. When one side is asleep the other will be put through its paces with a series of simple tests of language and memory. The aim is to establish whether the right hemisphere, which looks healthy, is indeed capable of normal levels of functioning. If not, the effects of surgery could be catastrophic. Our patient lies a few feet away on the operating table. She adjusts her glasses and I catch a quiver of the lips. On the X-ray monitor, the spectacles wobble but the skull keeps a fixed grin. I feel a surge of empathy for the bones.
Sitting beside me are Es Devlin, a stage designer, and Tom Gidley, an artist and filmmaker. The three of us are researching a drama about neurological patients. We were introduced to Julie about an hour ago when she was having the electrodes attached to her head in the EEG room. Es notes that the operating table looks like a magician's prop. "Well," I say, "we are about to saw the lady in half." The magician is Gus Baker, clinical neuropsychologist. Like Es and Tom, I'm here merely to observe. But I'm also a neuropsychologist. I've run plenty of Wada procedures, and I'm pleased when Gus invites me to muck in. I'll help out with timing and monitoring responses. Am I an observer now or a participant? Participant I think, because suddenly I feel tired.
It was a late night. I gave a talk in Cheltenham and had an early call for the train. They'd put me up at a hotel ten minutes walk from the venue but I took a wrong turning and half an hour later was still wandering the empty streets like a figure in a de Chirico nightmare. Cheltenham after midnight is an elegant mausoleum. Having drunk two coffees before my talk and two beers after, I couldn't sleep. My head was still buzzing. I have never before lectured to an invisible audience. The ferocious stage lighting dissolved the auditorium into an inky void. It was like talking to myself, a curiously private experience - apposite, perhaps, since one of my themes was the impermeable unity of subjective self-awareness. We tend to think of ourselves as singular, conscious beings, inhabiting a particular body - the same thing, in essence, from one moment to the next, one day to the next, across a lifetime. I'd projected some diagrammatic images of a Wada procedure to illustrate the fragility of this assumption. If you present an object to the right hemisphere while the left hemisphere sleeps the left will subsequently deny knowledge of the experience. But if you then ask the patient to select the object from a random array of alternatives using her left hand (which is controlled by the "knowing" right hemisphere), the chances are she will pick the correct item - a literal example of the right hand not knowing what the left is up to. Memory and the control of action are clearly fragmented, but what's happening to "the person"? Where's the unity?
And what's happening to Julie now? The drug has been injected and half her brain - the articulate left side - is temporarily out of commission. "Twenty-four" is the only word in her lexicon. It's rolling around a vast, empty brain chamber. The number of possible questions is infinite but Julie has just one answer at her disposal. "So," says Gus showing her one of the test stimuli, "tell me what you can see in this picture." "Twenty-four," says Julie. "Twenty-four, umm, twenty-four." Her responses are subdued and effortful. Then, when the right brain is suppressed and words fizz up from the left we see a more extroverted character. She becomes disinhibited. "Ooh, I'm a bit giggly." Gus tries to get her back on track, but she's all eyes. "You're a good-looking guy," she says. There is relief all round when the proceedings reach a successful conclusion. "Did I pass?" "With flying colours," says Gus. The bespectacled skeleton is elated. Well done, Julie. Both of you.
