I have something in mind--a thought so evanescent that it comes and goes in milliseconds.
To capture it in the act, UCLA neuroscientist Mark S. Cohen has trained on my brain a 22-ton experimental imaging device, twice as powerful as--and 30,000 times faster than--any conventional medical imager. This nuclear magnetic resonance (NMR) imager generates a magnetic field so forceful that, as it pulses and flexes around my head, the room shakes with a 100-decibel pile-driver roar.
Every 50 milliseconds, it captures an image of the physical spark of my imagination at work--and something more.
Only part of my conscious mind attends to the mental exercise that Cohen is recording. The rest is abuzz--worried whether I can perform the task properly, curious about how well my mind will photograph, and wondering most of all about the motives of these scientists who are so intent on the neurobiology of my thoughts.
This irrepressible mental chorus constitutes the background noise in the NMR image Cohen takes of my brain. It is also the core of the most perplexing problem in science: What is consciousness?
The human brain, and the self-awareness that arises from it, is a mystery wrapped in an enigma, swaddled in a tough, protective membrane and sealed inside the skull, unknowable until now except by the most indirect means.
Until recently, only a surgeon ever saw an exposed, living brain. A neuroscientist could learn more about its intangible mental functions by reading poetry or arguing philosophy than by examining the dead organ on an autopsy table.
Today, scientists have at hand an array of exotic devices that can peer through the skull to catch the living brain at work. Researchers at UCLA and other centers are using them to explore one of the last uncharted territories: the structure and cognitive functions of the human brain.
Emboldened by their ability to capture the image of something as intangible as imagination, a growing number of scientists are trying to study the one thing that many believe cannot be labeled, scrutinized or even defined--human consciousness.
The effort to understand human consciousness is an inquiry older than science itself. It is at the heart of a riddle of identity that has preoccupied philosophers, mystics and theologians for as long as there have been words to frame the query: Who--or what--am I?
Many neuroscientists hope that by studying the neurons of the brain, its genes, sensory perceptions, memory and language systems, they may be able to collect enough information about the way it works to finally discover the organizing principles underpinning all subjective experience.
Consequently, researchers for the first time feel confident enough to frame serious questions about the physical foundations of the human spirit.
How do the physical processes of the brain give rise to subjective experience?
Somehow, the fragile synapses and cells of the human nervous system can perceive the world around them, learn from their perceptions, reinforce memories with the force of emotion, plan ahead, decide and act on incomplete information, as well as sleep, dream, wake and pay attention.
The brain captures its moods in melodies. It invents stock markets, founds religions and orbits telescopes. It is introspective enough to develop psychoanalysis.
"There is something very mysterious about consciousness," said Christoff Koch, a theoretical neurobiologist at Caltech. "Why can objective physical systems have subjective states? It is baffling.
"It gets at the central idea of the soul."
For the human brain, the scientific investigation of consciousness is the beginning of an unusual journey of self-discovery.
"We are trying to understand who we are by studying the organ that allows you to understand who you are," said Antonio Damasio, an expert at the University of Iowa on the brain, cognition and behavior.
"Consciousness," said David Chalmers, a cognitive scientist and philosopher at UC Santa Cruz, "is the last frontier of science."
Chemistry and Electricity
Unraveling the nature of consciousness, however, is a problem too daunting for any one scientist to address in its entirety.
Instead, researchers are teasing apart isolated neural processes, such as how the brain perceives color or how neural cells focus attention, in the hope that they can gather evidence of how a conscious mind is assembled from different brain processes.
On scores of university campuses, scientists trace the ebb and flow of chemicals that trigger brain functions, the blood flows that nourish them and the electrical patterns they generate. They are trying to catch the mind in the act of being.
*
As they pull together new insights into how the brain functions, a growing number of neuroscientists believe that the mental processes underlying consciousness arise from an intricate madrigal of two languages--chemistry and electricity--communicated through networks of millions of neurons, all orchestrated precisely in time.
