Watching the brain at work

WE STILL have a lot to learn about the human brain, and physics is providing us with some powerful new methods for exploring how this remarkable organ works. Neuroscientists can, for example, monitor the electrical activity of nerve cells in the brain using electroencephalography, which records the electrical potential on the scalp, or with magnetoencephalography, which measures the weak magnetic fields generated just above the scalp by current flow in the brain. It is also possible to monitor the indirect effects of neural activity, such as changes in blood flow and oxygenation, using near-infrared spectroscopy, positron emission tomography and magnetic resonance imaging (MRI).