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Web Exclusives: PawPlus
September 10, 2003: Brain
sensors or literary critics For the article printed in the September 10th issue of PAW, click here. I won't pretend I can write like Paul Muldoon. But I might be able to make more interesting pictures. Many of the spectacular achievements of 20th-century science followed a simple paradigm. As new directions in basic atomic or molecular physics matured, they were adopted by chemists and applied physicists. This work in turn enabled applications in biological, clinical, and environmental science. The centers I direct at Princeton (including POEM, the center for Photonics and Optoelectronic Materials) support this process by bridging the gaps between innovation, technology, and application. Imaging technologies provide many of the best-known illustrations of this evolution. Fifty years ago, measurements of the magnetism created when atomic nuclei "spin" were at the forefront of esoteric physics research, with no conceivable application. Gradually the applications became clear, and by the 1960s, every modern chemistry department had "nuclear magnetic resonance" spectrometers. By the 1980s, most hospitals had "magnetic resonance imagers" ("nuclear" was dropped to avoid scaring patients) which give beautifully detailed images of soft tissue. Imaging function, not just structure, is the modern research frontier, and new methods are unraveling the workings of the brain. The black and white images below come from a conventional MRI of a volunteer, similar to what you would get in a hospital. The slice at right (located at the position of the yellow line at left) shows colored dots at points that differed when the volunterr read Muldoon's poem verses a non-emotive text. This activation in the prefrontal cortex is no surprise: It is the most evolved part of the brain, and a center of both critical and emotional response. More extensive studies (with multiple subjects and multiple tasks) can give better spatial resolution. In recent papers, scientists have imaged differences in the brain activation between viewing a lover and viewing an opposite-sex friend; between male and female perceptions; and between moral reasoning and simple decision-making. Some would say that the mind-imaging revolution threatens to convert the field of psychology into a quantitative science over the next few decades. For this to happen, new technological advances must improve both spatial and temporal resolution. One promising advance involves lasers. Starting with a very short lump of light (in time), we can sculpt pulses that quickly change amplitude and color in complex patterns. The figure at right shows the "gremlin pulse," a very simple pulse used in my laboratories to test shaping capabilities (we can actually program hundreds of features simultaneously). One application of shaped pulses is "making molecules dance," or producing just the right color and time distribution to excite specific compounds. A related application is imaging. The human body is almost transparent at specific near-infrared wavelengths, just slightly outside of the visible region (but easily detected by modern instruments), and subtle brain changes can change the amount of transmitted light. Unfortunately, light scattering currently makes high-resolution pictures impossible. Pulse shaping may provide an attractive solution, allowing low power lasers to see through scattering and find hidden chemical signals. We are not yet able to probe truly deep questions (brain sensors
will not replace literary critics for some time). Still, the evolving
ability to image the mind has enormous consequences that range far
beyond neuroscience. The world needs more poets who follow science,
and more scientists who learn to appreciate beauty in words.
Warren S. Warren
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