The big advance will be to develop functional imaging techniques that show us-as it is happening-how various areas of the brain interact.
With great knowledge in neuroscience comes great responsibility. The emerging field of neuroethics has begun to focus on the ethical implications of our increased ability to understand and change the brain. Neuroscientists are joining with other scientists, other professionals, and concerned citizens to consider how this power can best be used for the greatest public good.
Neurologist Guy M. McKhann, M.D., of Johns Hopkins University, predicts great advances in the next few decades in imaging, which actually now does not take place in real time with brain activity-that is, the images show brain systems' activity milliseconds after it begins. "The big advance," he says, "will be to develop functional imaging techniques that show us-as it is happening-how various areas of the brain interact. That is, we will see not only the location of brain activity but also its speed. Whatever the method, this souped-up imaging will enable us to investigate how brain circuits work, how one part of the brain modifies the functions of other parts, and how these circuits adapt to new situations or damage to existing circuits."
Dr. McKhann also says that we will be able to use imaging to study cell transplants in the brain. "Transplanted cells and their changes can be tracked by molecules on their surfaces. Specific markers can be attached to those molecules as tags that can be spotted by imaging, like radio collars on wolves moved to a new terrain. Other cells, scavenger cells that are part of our immune system, can be tracked into and out of the brain as they respond to injury or to therapies."
Dr. Insel says that recent advances have enhanced our ability to visualize individual cells, even in the living brain. "In addition," he says, "both structural and functional studies of the whole brain have been enhanced to allow neuroscientists to identify pathways for information in the brain. With imaging we can map the remarkable plasticity in the human cortex, the circuits for processing faces and language and even the evidence for information that is encoded without any conscious awareness. Marcus Raichle, M.D., a pioneer in brain imaging, says that "several issues are likely to be of increasing importance to our future understanding of human brain function and likely will receive increasing attention from the neuroimaging community. These include individual differences, development (brain maturation), and the activities of the "resting brain."
"I ask myself how many of the advances in the last 25 years of brain science I would have predicted," says Dr. McKhann. "Not many. Some came from logical, sequential explorations of how the brain works. Others were great leaps that kicked over strongly held beliefs. Others came through luck, albeit the luck of very patient and alert investigators. The same combination will shape the next 25 years of brain research."
Brain Imaging: A Closer Look
Computer technology has opened a window on the living brain. Before the early 1970s, only neurosurgeons had seen a living human brain. Rapid advances in computer-generated imaging have allowed brain scientists and doctors to go inside the head and examine the structure and function of the brain in the living patient. Advances in the next few decades are expected to allow scientists to investigate how brain circuits work, how one part of the brain modifies the functions of other parts, and how these circuits adapt to new situations or damage to existing circuits.
Chapter 2: Genes and the Brain
Imagine a homework assignment in which you must read and understand the “Book of Life,” a story with 3.3 billion letters. Printed out, the letters would fill a volume of books that would reach as high as the Washington Monument. Oh, and the letters are all either A, C, G, or T, arranged in seemingly endless combinations. Some of the “words” are millions of letters long, and you’ll need to figure out where one ends and another begins. Then you’ll need to find out what the words mean (there’s no dictionary), and how they interplay with all the other words in the book.
That is essentially the task that was undertaken by the Human Genome Project, a government-funded effort to “read” the human genome, and a parallel effort by Celera Genomics, a private company. The genome contains the complete instruction manual for Homo sapiens, written in chemical code along the twisted double-helix strands of DNA that are carried within each of the 100 trillion cells in the human body (except in mature red blood cells).
The mapping and sequencing of the human genome, completed in 2003, culminates nearly five decades of investigation following the first description of the double-helix model of DNA by James D. Watson and Francis Crick in 1953. Watson and Crick’s view of DNA successfully described how molecules of nucleic acid could not only carry tremendous amounts of information, but could also copy themselves accurately each time a cell divides.
With the mapping and sequencing of the human genome, for the first time scientists can see the entire landscape of all the human chromosomes and how the genes are organized on the chromosomes. Encoded in the twists of our DNA are about 30,000 genes, the critical “words” in the Book of Life. They determine every inherited trait we have, from the color of our eyes to the size of our feet, and possibly even behavioral traits such as an inclination to be aggressive or our desire for affection. More important, they tell us what diseases we may be susceptible to and those we may be protected from, as well as what medicines we might respond to in the event of illness.
In short, understanding the Book of Life has the potential to change everything about health, medicine, and life in general. Welcome to the Genomics Era.
Genomics will affect every field of medical science, but its significance to brain science is particularly great. As much as half of the genome’s instruction manual—as many as 15,000 genes—is thought to be devoted to the workings of the central nervous system (the brain and spinal cord) and peripheral nerves. One surprise of the genome projects was that humans have only about twice as many genes as fruit flies and roundworms, two “simpler” species used as models for biological systems in science and medicine. Many of the “extra” genes in humans are thought to be devoted to the development, structure, and function of the brain—a testament to the complexity of the organ that most differentiates us from every other living thing on earth.
Not So Different from a Fruit Fly
Still, experts remind us that at the level of individual brain cells (neurons) we’re not all that different from fruit flies. Many of the most basic mechanisms of brain function—how cells communicate with one another or how memories are processed, among others—are basically the same in humans and fruit flies, as well as in mice, chimpanzees, and other species. In the spirit of “if it’s not broken, don’t fix it,” such processes have been conserved by the forces of evolution. Much of the human brain’s complexity is more likely a result of our having so many more neurons interconnected in so many more ways. Think of it as your home PC versus a huge supercomputer: the basic operating systems are the same, but the supercomputer has far more processing power.
The sequencing of the human genome—and, more important, determining the function of all those genes—will reveal the brain’s deepest secrets: why we act the way we do; why some things are easier to learn than others; how our brain develops from conception through adulthood, including the critical teenage years when the brain undergoes a dramatic “pruning” process to streamline its circuits. It will also give us new information about the genetic components of brain diseases, which include a wide array of disorders ranging from attention deficit disorder to Alzheimer’s disease and mental illnesses such as depression and schizophrenia. Scientists have struggled for years to find the genes at the root of many of these brain disorders; with the sequence in hand, the searches will be much speedier.
الإثنين يناير 12, 2015 2:09 am من طرف نبراس جميل
موضوع: the brain interact 
