t has been described by the Nobel Laureate James Watson as "the most complex thing we have yet discovered in our universe." He speaks of the human brain: three pounds of protoplasm, tens of billions of neurons, trillions of synaptic connections. Out of this complex mass emerge will, consciousness, behavior and personality—the sum total of what it means to be human.
But for centuries, the brain has remained a virtual mystery, the least-understood function of human anatomy. Scientists probing the workings of the brain were limited to a minimal set of tools and choices. They could study the effects of brain lesions on personality and cognition, use electroencephalograms to gauge the electrical activity of the brain or simply take the brain apart upon autopsy and attempt to deduce from the remains the function of the living brain. In sum, it was rather like trying to describe an object in the darkness through touch.
The last 25 years, however, have seen a singular revolution in our understanding of the form, function and pathology of the brain. Research has succumbed to an interdisciplinary approach, stretching from neuroanatomy and cellular and molecular biology to psychology, neuropharmacology and classical cognitive science. But no single advance has done more to further our knowledge than the development of a new armamentarium of brain-imaging technologies all but nonexistent just two decades ago.
The 1970s saw the advent of computer-aided tomography, or CT scans, that allow researchers to make three-dimensional X-ray images of the brain and to dramatically increase the diagnostic efficacy of X-ray technology. Positron-emission tomography, or PET scanning, on the other hand, allows researchers for the first time to study brain function as well as structure (see "Mapping the Brain," Challenge, 1994). PET takes the signals emitted by radioactive tracers injected into the bloodstream and turns them into striking cross-sectional pictures depicting everything from cerebral blood flow to the brain metabolism of oxygen and glucose to a range of neurotransmitters and other molecules.
But by far the most rapid and startling advances have come from the range of noninvasive technologies encompassed by magnetic resonance imaging (MRI)—including magnetic resonance spectroscopy and, most recently, functional magnetic resonance imaging. Combined with the exponential advances made in computer technology, these have led to stunning images of brain function and form.
MRI scanners work with powerful magnetic fields that prompt the protons of hydrogen atoms in the water in living tissue to emit weak radio signals. These signals, in turn, are detected and assembled by computer into images. Where X-rays reveal only shadows of bones or tumors, MRIs can differentiate between tissues of different chemical compositions and varying degrees of hydrogen concentration, resulting in two- or even three-dimensional images of a living brain.
Magnetic resonance spectroscopy, which induces signals from the protons in a wide variety of atomic nuclei, not just the hydrogen atoms of water, allows researchers to image the chemical composition of the brain. And the very latest advances come from functional MRI, which can induce and then detect radio signals emitted by the oxygen in the brain, the levels of which will rise and fall in response to brain activity, providing a measure of the dynamics of brain function and leading to breakthroughs in understanding how the brain divvies up cognitive tasks into its component parts.
From the research laboratory to the clinical setting and even into the operating room, UCLA researchers and clinicians have put these new technologies to work to develop a new understanding of brain function, new diagnostic techniques and revolutionary new approaches to treatment that are nothing short of remarkable.
