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Neuroscience (289)
NROB60H3 (151)
Chapter 1


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Diane Mangalindan

CHAPTER 1: Neuroscience: Past, Present, and Future The Orgins of Neuroscience:  As early as 7000 years ago, people were boring holes in each others skulls (technique called trepanation)  This was done with the aim not to kill but to cure  The skulls show signs of healing after the operation indicating that this procedure was carried out on live subjects and was not merely a ritual conducted after death  Some have speculated that this procedure may have been used to treat headaches or mental disorders, perhaps by giving the evil spirits an escape route  Recovered from writings from the physicians of ancient Egypt dating back to almost 5000 years, it was clear that the heart, not the brain was considered to be the seat of consciousness and thought  This idea was not seriously challenged until the time of Hippocrates Views of the Brain in Ancient Greece  Different parts of your body look different because they serve different purposes  Thus we can say that there appears to be a very clear correlation between structure and function  Differences in appearance predict differences in function  The most influential scholar was Hippocrates, the father of western medicine, who stated his belied that the brain not only was involved in sensation but also was the seat of intelligence  This view although was not universally accepted  The famous greek philosopher Aristotle clung to the belief that the heat was the center of intellect and proposed the brain to be a radiator for the cooling of blood that was overheated by the seething heart Views of the Brain During the Roman Empire  One of the most important figures in roman medicine was the greek physician and writer Galen  Galens opinions about the brain probably were influenced more by his many careful animal dissections  Two major parts of the brain were evident in galens depiction of the brain : the cerebrum in the front and the cerebellum in the back  Just as we were able to deduce function from the structure of the hands and feet, galen tried to deduce function from the structure of the cerebrum and the cerebellum  Poking the brain with a finger reveals the cerebellum to be rather hard and the cerebrum to be rather soft  From this observation, galen suggested that the cerebrum must be the recipient of sensations and the cerebellum most command the muscles  In reality, the cerebrum is largely concerned with sensation and perception as well as a repository for memory and the cerebellum is primarily a movement control center  How odes the brain receive sensations and move the limbs?  Galen cut open the brain and found that is is hollow  In these hollow spaces, called ventricles, there is fluid  Sensations were registered and movements initiated by the movement of humors to or from the brain ventricles via the nerves, which were believed to be hollow tubes like the blood vessels Views of the Brain from the Renaissance to the Nineteenth Century  More detail was added to the structure of the brain by the great anatomist andreas Vesalius during the renaissance  In the early seventeenth century, French inventors began developing hydraulically controlled mechanical devices – these devices supported the notion that the brain could be machine-like in its function (fluid forced out of the ventricles through the nerves might literally ‘pump you up’ and cause movement of the limbs  A chief advocate of this fluid-mechancical theory of brain function was the French mathematician and philosopher Rene Descartes  He reasoned that unlike other animals, people possess intellect and a god- given soul  Thus, Descartes propsed that brain mechanisms control human behavior only to the extent that this behavior resembles that of the beasts  Descartes believed that the mind is a spiritual entity that receives sensations and commands movements by communicating with the machinery of the brain via the pineal gland  Today people still believe that there is a mind-brain problem and that somehow the human mind is distinct from the brain  Modern neuroscience research supports the conclusion that: the mind has a physical basis, which is the brain  Other scientists during the seventeenth and eighteenth century began to give substance of the brain a closer look  One of their observations was that brain tissue is divided into two parts: the gray matter and white matter  White matter, because it was continuous with the nerves of the body, was correctly believed to contain the fibers that bring information to and from the gray matter  By the end of the eighteenth century, the nervous system has been completely dissected, and its gross anatomy has been described in detail  Scientists recognized that the nervous system has a central division, consisting of the brain and spinal cord, and a peripheral division, consisting of the network of nerves that course through the body  An important breakthrough in neuroanatomy was the observation that the same general pattern of bumps (called gyri) and grooves (called sulci and fissures) could be identified on the surface of the brain in every individual  This pattern, which enables the parceling of the cerebrum into lobes, was the basis for speculation that different function might be localized to the different bumps on the brain Nineteenth- Century Views of the Brain  By the end of the eighteenth century, the state of understanding of the nervous system was this:  Injury to the brain can disrupt sensations, movement, and thought and can cause death  The brain communicates with the body via the nerves  The brain has different identifiable parts, which probably perform different functions  The brain operates like a machine and follows the laws of nature  Four key insights gained during the nineteenth century: 1. Nerves as Wires:  Italian scientist Luigi Galvani and german biologist emil du bois- reymond had shown that muscles can be caused to twitch when nerves are stimulated electrically and that the brain itself can generate electricity  These discoveries finally displaced the idea that nerves communicate with the brain by the movement of fluid  New concept: nerves are “wires” that conduct electrical signals to and from the brain  What they didn’t know was if the signals to the muscles causing movement use the same wires as those that register sensations from the skin  Bidirectional communication along the same wires was suggested by the observation that when a nerve in the body is cut, there is usually a loss of both sensation and movement in the affected region  Also known that within each nerve of the body there are many thin filaments, called nerve fibres, each one of which could serve as an individual wire carrying information in a different direction  Just before the nerves attach to the spinal cord, the fibers divide into two branches, or roots  The dorsal root enters toward the back fo the sinal cord and the ventral root enters toward the front  This was discovered by Scottish physician Charles bell and French physiologist, francois magendie  Bell tested the probability that these two spinal roots carry information in different direction by cutting each root separately and observing the consequences in experimental animals  He found that cutting only the ventral roots caused muscle paralysis and later, magendie was able to show that the dorsal roots carry sensory info into the spinal cord  Magendie and Bell conclusion: within each nerve there is a mixture of many wires, some of which bring information into the brain and spinal cord, and other that send info out to the muscles  In each sensory and motor nerve fiber, transmission is strictly one-way  The two kids of fibers anatomically segregate when they enter or exit the spinal cord 2. Localization of Specific Functions to Different Parts of the Brain  Bell proposed that the origin of the motor fibers is the cerebellum and the destination of the sensory fibers is the cerebrum  A way to test this proposal is to destroy the parts of the brain and test for motor and sensory deficits  When parts of the brain are systematically destroyed to determine their function is called experimental ablation method  Pierre flourens used this method in a variety of animals to show that the cerebellum does indeed play a role in coordination of movement and also concluded that the cerebrum is involved in sensation and perception  Franz joseph gall believed that belived that the bumps on the surface of the skull reflect the bumps on the surface of the brain  He proposed that the propensity for certain personality traits, such as genoristy or secretiveness, could be related to the dimensions of the head  This new science of correlating the structure of the head with personality traits was called phrenology  one of the most vociferous critics for phrenology was flourens – he performed experimental blations showing that particular traits are not isolated to the portions of the cerebrum specified by phrenology  paul broca was presented with a patient who could understandlanguage but couldnot speak  following the mans death, broca carefully examined his brain and found a lesion in the left frontal lobe  broca concluded that this region of the human cerebrum was specifically responsible for the production of speech  Gustav Frisch and eduard hitzig showed that applying small electrical currents to circumscribed region of the exposed surface of the brain of a dog culd elicit discrete moevments  David Ferrier repeated the same experiments except on a monkey and showed that the removal of the same region of the cerebrum causes paralysis of the muscles  Hermann Munk used e
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