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ScienceWeek
HISTORY OF BIOLOGY: ON THE DEVELOPMENT OF NEUROSCIENCE
The following points are made by Carl Zimmer (Science 2004 303:43):
1) History has a way of repeating itself -- even the history of science. Today we are witnessing a revolution in neuroscience, as researchers chart the circuitry of memory, cognition, and emotion, offering the promise of a chemically based medicine of the mind (1). But these same words would have been just as apt over 300 years ago, when neurology first emerged as an experimental science (2). In the mid-1600s, humanity's understanding of the brain changed no less profoundly than it is changing today. Medieval concepts of the soul and spirits rapidly disappeared, replaced with a vision of the brain based on anatomy, chemistry, and physics.
2) Gazing into this distant mirror, we can see how many of the themes of modern neuroscience can actually be traced back to a time long before the luxuries of electroencephalograms (EEG) or magnetic resonance imaging (MRI) existed. We can admire the brilliance of the minds that created a science of the mind itself. But not everything we see in this mirror is beautiful. The first neurologists did not hesitate to leap from scant evidence to wild speculation. They believed that the biology of the brain justified the social divide between the powerful and the powerless. And although they promised that neurology would usher in new treatments for madness and other mental disorders, they did nothing of the kind: In the late 1600s, neurology often served as a new bottle for ancient wines.
3) It is difficult to appreciate just how unimportant the brain was considered to be before the scientific revolution. Medieval and Renaissance physicians sought to understand the mind with a mix of Christian theology and Greek philosophy. The body was believed to be divided into three anatomical regions, each designed for its own soul. The vegetative soul in the liver was responsible for desires and appetites. The heart housed the vital soul, which produced passions and action. The rational soul was immaterial and immortal and, hence, could not reside in one specific place in the body. But its faculties -- such as reason, memory, and imagination -- were carried out by the body's invisible spirits. These spirits were believed to swirl in three hollow chambers in the head known as the ventricles (3).
4) Anatomy, then, was the study of the houses of the souls. But anatomy alone was not enough to account for the life of the mind. Physicians also had to understand the fluids that coursed through the body. The four humors -- black bile, yellow bile, blood, and phlegm -- needed to be balanced for good health. Humors also gave each individual his or her temperament, be it the sad detachment of melancholy or the swift rage of choler. If the humors became corrupted or moved to the wrong place in the body, they could cause epilepsy or alter the temperament, even lead to madness. Physicians sought to cure many psychological disorders by bringing the humors back in balance, typically with bleeding and purging or by applying herbs.(4,5)
References (abridged):
1. E. R. Kandel, L. R. Squire, Science 290, 1113 (2000)
2. S. Finger, The Minds Behind the Brain (Oxford Univ. Press, New York, 2000)
3. R. K. French, Dissection and Vivisection in the European Renaissance (Ashgate, Aldershot, UK, 1999)
4. M. MacDonald, Mystical Bedlam: Madness, Anxiety, and Healing in Seventeenth-Century England (Cambridge Univ. Press, New York, 1981)
5. R. Frank, Harvey and the Oxford Circle (Univ. of California Press, Berkeley, CA, 1980)
Science http://www.sciencemag.org
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ON THE RECENT HISTORY OF NEUROSCIENCE
The following points are made by E.R. Kandel and L.R. Squire (Science 2000 290:1113):
1) The authors point out that during the latter part of the 20th century, the study of the brain moved from a peripheral position within both the biological and psychological sciences to become an interdisciplinary field called "neuroscience" that now occupies a central position within each discipline. This realignment occurred because the biological study of the brain became incorporated into a common framework with cell and molecular biology on the one side and with psychology on the other side. Within this new framework, the scope of neuroscience ranges from genes to cognition, from molecules to mind.
2) Concerning developments in neuroscience during 1990-2000, the authors identify the following important research advances:
1990: a) Segi Ogawa et al developed functional magnetic resonance imaging. b) Mario Capecchi and Oliver Smythies developed gene knockout technology, which was soon applied to neuroscience.
1991: a) Linda Buck and Richard Axel discovered that the olfactory receptor family consists of over 1000 different genes. b) The anatomical components of the medial temporal lobe memory system were identified.
1993: The Huntington's Disease Collaborative Research Group identified the gene responsible for Huntington's disease.
1990s: a) Neural development was transformed from a descriptive to a molecular discipline by Gerald Fischbach, Jack McMahan, Tom Jessell, and Corey Goodman. b) Neuroimaging was applied to problems of human cognition, including perception, attention, and memory. c) Reinhard Jahn, James Rothman, Richard Scheffer, and Thomas Sudhof delineated the molecules critical for exocytosis.
1998: The first 3-dimensional structure of an ion channel is revealed by Rod MacKinnon.
3) The authors conclude: "The neuroscience of higher cognitive processes is only beginning. For neuroscience to address the most challenging problems confronting the behavioral and biological sciences, we will need to continue to search for new molecular and cellular approaches and use them in conjunction with systems neuroscience and psychological science. In this way we will best be able to relate molecular events and specific changes within neural circuits to mental processes such as perception, memory, thought, and possibly consciousness itself."
Science http://www.sciencemag.org
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Notes:
functional magnetic resonance imaging: (fMRI) There is a difference between magnetic resonance imaging (MRI) and "functional" magnetic resonance imaging (fMRI) as applied to the brain. The former is essentially a technique for examining morphology, while the latter is a technique for examining activity of brain tissue. Both techniques involve computerized analysis of data. In general, MRI involves magnetic coils producing a static magnetic field parallel to the long axis of the patient or subject, combined with inner concentric magnetic coils producing a static magnetic field perpendicular to the long axis. A radio-frequency coil specifically designed for the head perturbs the static fields to generate a magnetic resonance image. The interaction physics in this technique is that between the magnetic fields and atomic nuclei in brain tissue. "Sliced" views can be obtained from any angle, and the resolution is quite high and on the order of millimeters for current magnetic field strengths of 1.5 tesla. Functional magnetic resonance imaging (fMRI), the variant of MRI discussed here, is based on the fact that oxyhemoglobin, the oxygen-carrying form of hemoglobin, has a different magnetic resonance signal than deoxyhemoglobin, the oxygen-depleted form of hemoglobin. Activated brain areas utilize more oxygen, which transiently decreases the levels of oxyhemoglobin and increases the levels of deoxyhemoglobin, and within seconds the brain microvasculature responds to the local change by increasing the flow of oxygen-rich blood into the active area. This local response thus leads to an increase in the oxyhemoglobin-deoxyhemoglobin ratio, which forms the basis for the fMRI signal in this technique. Because of its high spatial resolution (millimeters) and high temporal resolution (seconds) compared to other imaging techniques, fMRI is now the technology of choice for studies of the functional architecture of the human brain.
gene knockout technology: In general, in this context, "knockout technology" involves the generation of a mutant organism (usually a mouse) with a missing specific gene.
Huntington's disease: (Huntington's chorea) First described by George Huntington (1850-1916), the disease attacks specific regions of the brain (e.g., caudate nucleus and putamen), and leads to insanity and eventual death.
exocytosis: This refers to the bulk transport of materials out of the cell across the cell membrane (plasma membrane). The process generally involves the encasing of the material within intracellular membranes, forming a "vacuole", and the subsequent transport of the vacuole to the cell surface. At the cell surface, the vacuole fuses with the plasma membrane, and the contents of the vacuole are deposited outside the cell. Various aspects of the process are visible with both light and electron microscopy in a variety of cell systems, and this is the process primarily responsible for excretion and secretion by individual cells.
ion channel: Ion channels are protein channels in cell membranes that allow ions to pass from extracellular solution to intracellular solution and vice versa. Most ion channels are selective, allowing only certain ions to pass, and an individual cell has ion channels with various ion selectivities. From an electrical standpoint, each ion channel is effectively a specific parallel conductance pathway through the cell membrane, and the dynamic electrical behavior of nerve cells is essentially directly determined by the opening and closing of its ion channels.
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