n a concrete basement at the University of Sydney, I sat in a chair waiting to have my brain altered by an electromagnetic pulse. My forehead was connected, by a series of electrodes, to a machine that looked something like an old-fashioned beauty-salon hair dryer and was sunnily described to me as a ''Danish-made transcranial magnetic stimulator.'' This was not just any old Danish-made transcranial magnetic stimulator, however; this was the Medtronic Mag Pro, and it was being operated by Allan Snyder, one of the world's most remarkable scientists of human cognition.

Nonetheless, the anticipation of electricity being beamed into my frontal lobes (and the consent form I had just signed) made me a bit nervous. Snyder found that amusing. ''Oh, relax now!'' he said in the thick local accent he has acquired since moving here from America. ''I've done it on myself a hundred times. This is Australia. Legally, it's far more difficult to damage people in Australia than it is in the United States.''

''Damage?'' I groaned.

''You're not going to be damaged,'' he said. ''You're going to be enhanced.''

The Medtronic was originally developed as a tool for brain surgery: by stimulating or slowing down specific regions of the brain, it allowed doctors to monitor the effects of surgery in real time. But it also produced, they noted, strange and unexpected effects on patients' mental functions: one minute they would lose the ability to speak, another minute they would speak easily but would make odd linguistic errors and so on. A number of researchers started to look into the possibilities, but one in particular intrigued Snyder: that people undergoing transcranial magnetic stimulation, or TMS, could suddenly exhibit savant intelligence -- those isolated pockets of geniuslike mental ability that most often appear in autistic people.

Snyder is an impish presence, the very opposite of a venerable professor, let alone an internationally acclaimed scientist. There is a whiff of Woody Allen about him. Did I really want him, I couldn't help thinking, rewiring my hard drive? ''We're not changing your brain physically,'' he assured me. ''You'll only experience differences in your thought processes while you're actually on the machine.'' His assistant made a few final adjustments to the electrodes, and then, as everyone stood back, Snyder flicked the switch.

A series of electromagnetic pulses were being directed into my frontal lobes, but I felt nothing. Snyder instructed me to draw something. ''What would you like to draw?'' he said merrily. ''A cat? You like drawing cats? Cats it is.''

I've seen a million cats in my life, so when I close my eyes, I have no trouble picturing them. But what does a cat really look like, and how do you put it down on paper? I gave it a try but came up with some sort of stick figure, perhaps an insect.

While I drew, Snyder continued his lecture. ''You could call this a creativity-amplifying machine. It's a way of altering our states of mind without taking drugs like mescaline. You can make people see the raw data of the world as it is. As it is actually represented in the unconscious mind of all of us.''

Two minutes after I started the first drawing, I was instructed to try again. After another two minutes, I tried a third cat, and then in due course a fourth. Then the experiment was over, and the electrodes were removed. I looked down at my work. The first felines were boxy and stiffly unconvincing. But after I had been subjected to about 10 minutes of transcranial magnetic stimulation, their tails had grown more vibrant, more nervous; their faces were personable and convincing. They were even beginning to wear clever expressions.

I could hardly recognize them as my own drawings, though I had watched myself render each one, in all its loving detail. Somehow over the course of a very few minutes, and with no additional instruction, I had gone from an incompetent draftsman to a very imp