CH1 Neuro - Lecture notes 1 PDF

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CHAPTER 1: An Introduction to Brain and Behavior -

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The Mind and its machine are shaped by a precise combination of genes and experience, inextricably tied together. The general field of neuroscience-the scientific study of the nervous system-is divided into many subdisciplines because the topic is so vast. Biological psychology, the field that related behavior to bodily processes, naturally evolved from those beginnings. The names behavioral neuroscience, brain and behavior, and physiological psychology are all synonyms for biological psychology. The main goal of this field is to understand the brain structures and functions that respond to experiences and generate behavior. The modern era of biological psychology-characterized by objective experimentation and use of the scientific method to test hypotheses-has a formal history of only 100 years or so. But curiosity about the genesis of behavior reaches much further into the past, shaped by religious ideas, folk knowledge, and ancient observations about the biology of humans and nonhuman animals. The behavioral role of the brain was uncertain to early scholars. In ancient Egypt, the brain was plucked out and unceremoniously discarded; apparently it was considered to be of no particular value in the afterlife. Aristotle (about 350 BCE), the most prominent scientist of ancient Greece, likewise considered mental capacities to be properties of the heart. Aristotle though the brain was little more than a cooling system for hot blood from the heart. The Greek physician, Hippocrates (about 400 BCE), already suspected that Aristotle’s view was wrongheaded, and he instead ascribed emotion, perception, and thought to the functioning of the brain. By the second century CE, this brain-centered view of mental processes had become more entrenched, appearing in the writings of the Greco-Roman physician Galen (the “Father of Medicine”). Galen’s experiences in treating head injuries of gladiators lead hum to propose that behavior results from the movement of “animal spirits” from the brain through nerves to the body. Skillfully applying newly developed innovations in drawing technique, Renaissance painter and scientist Leonardo da Vinci (1452-1519) produced exquisite neuroanatomical illustrations of nerves and brain structures. Galileo: with the result that scientific writing from that era often presents the brain as a mysterious and intricate gift from God. Michelangelo was conducting dissections of cadavers at the time the painting was created. He had a more secular view of neuroscience. René Descartes (1596-1650) tried to explain how the control of behavior might resemble the workings of a machine, proposing the concept of spinal reflexes and a neural pathway for them. He also argued that free will and moral choice could not arise from a mere machine. Descartes asserted that humans, at least, had a nonmaterial soul as well as a material body and that the soul governed behavior through a point of contact in the brain.

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This notion of dualism spread widely and left other thinkers with the task of trying to explain how a nonmaterial soul could exert influence over a material body and brain. Dualism: The notion, promoted by Rene Descartes, that the mind has an immaterial aspect that is distinct from the material body and brain. Today, biological psychologist reject dualism and favor a much simpler view that the working of the mind can be understood as purely physical processes taking place in the material brain. Due to systematic studies of the relation between various disorders and damage to regions of the human brain that were conducted by English physician Thomas Willis (1621-1675), the notion that the brain coordinates and controls behavior eventually became widely accepted. A pseudoscientific fad of the early 1800s called phrenology capitalized on the emerging idea that specific behaviors, feelings, and personality traits were controlled by corresponding specific regions of the brain. Although phrenology was fundamentally wrong in that it was believed that phrenologists could “read” a person by feeling bumps on that person’s head, the field helped establish the concept of localization of function, which asserts that different brain regions specialize in specific behaviors. Paul Broca (1824) noted that damage to a particular region of the left side of the reliably causes problems with speech production. Neuroscientists today accept that the localization of function within the brain is more or less true. Although the whole brain is active most of the time, when we are performing particular tasks, certain brain regions become even more activated, and different tasks activate different brain regions. Modern functional maps of the human brain track the locations where these peaks of activation occur. After a couple of centuries of study, the evidence indicates that while the overall size of your brain matters, it matters a lot less then you might expect. In 1890, William James’s book Principles of Psychology, his work in psychological activities such as consciousness and other aspects of human experience came to be seen as properties of the nervous system. Rapid progress was made in developing techniques for measuring learning and memory in humans and animals. Russian psychologist Ivan P. Pavlov (1849-1936) made his landmark discoveries of classical conditioning in animals-Nobel Prize-winning work that influences scientists to this day. Rapid progress prompted a parallel interest in understanding the neural basis of learning, marked by one of the first true biological psychology research programs: the “search for the engram” by Karl Lashley (1890-1985). Although he would not accomplish his of linking a specific brain region to the formation of a specific long-term memory (an engram), Lashley gave us the idea that memory is not localized to only one region of the brain.

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Donald O. Hebb (1904-1985), one of Lashley’s students, had a particularly profound impact on biological psychology. Hebb showed that cognitive processing could be accomplished by networks of active neurons, molded by repeated activation patterns into functional circuits. His hypothesis about how neurons strengthen their connections as a consequence of experience led to the idea of the Hebbian synapse, a type of plastic connection between neurons. Present-day biological psychologists may draw on several different theoretical perspectives. Here are some of the major ones 1) Systematic description of behavior: Until we describe what we want to study, we cannot accomplish much. Depending on our goals, we may describe behavior in terms of detailed acts or processes, or in terms of results or functions. To be useful for scientific study, a description must be precise, using accurately defined terms and units. 2) The evolution of brain and behavior: Darwin’s theory of evolution through natural selection is central to all modern biology and psychology. Biological psychologists employ evolutionary theory in two ways: by evaluating similarities among species due to shared ancestry, and by looking for species-species differences in behavior and biology that have evolved as adaptations to different environments. 3) Life-span development of the brain and behavior: Ontogeny is the process by which an individual change in the course of its lifetime. Observing the way a particular behavior changes during ontogeny may give us clues to its functions and mechanisms. Studying the development of reproductive capacity and of differences in behavior between the sexes, along with changes in body structures and processes, enables us to throw light on body mechanisms underlying sexual behaviors. 4) The biological mechanisms of behavior: To learn about the mechanism of an individual’s behavior, we study how his or her present body works, separate from evolutionary or developmental concerns. To understand the underlying mechanisms of behavior, we must regard the organism as a “machine,” made up of billions of nerve cells, or neurons. In a sense, the mechanistic questions are the “how” questions of biological psychology, in contrast to the “why” questions that derive from the evolutionary and developmental perspectives. So in the case of learning and memory, we might try to understand how a sequence of electrical and biochemical processes allows us to store information in our brains, and how a different process retrieves it. The future of biological psychology is in interdisciplinary discovery and knowledge transition. At least one in five suffers a neurological or psychiatric illness. The toll of these disorders is enormous: just the cost for the treatment of dementia alone exceeds the costs of treating cancer and heart disease combined. When you think about it, the only explanation for our ability to learn skills and form memories is that the brain physically changes in some way to encode and store that information. Neuroplasticity, also called neural plasticity, is the ability of the nervous system to change in response to experience or the environment.

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We know that experiences can alter the size of brain regions and interconnections between neurons, and cellular changes have been discovered that could be mechanisms for storing memories; scientists are actively testing that idea. We also know that certain experiences and physiological states can modify the rate at which new neurons are born in the adult brain, but again, the functional significance of this adult neurogenesis remains to be determined. Adult neurogenesis: the creation of new neurons in the brain of an adult. Because of neuroplasticity, even simple interactions with other people can remodel our brains. Most aspects of our social behavior are learned-from the language we speak to the clothes we wear and the kinds of foods we eat, as well as our identity in belonging to larger groups. Social neurosciences is an emerging discipline that uses the tools of neuroscience to discover how biological and social factors continually interact and affect each other as behavior unfolds. Speculations about how natural selection might have shaped our own behavior, including specific cognitive abilities, have given rise to a lively and controversial field called evolutionary psychology. Evolutionary psychology: A field of study devoted to asking how natural selection has shaped behavior in humans and other animals. It has been argued that sexual selection was crucial for evolution of the human brain. Nearly all of the cells in your body have a complete copy of your genome, but each cell uses only a small subset of those genes at any one time. Epigenetics is a young field focusing on factors that have a lasting effect on patters of gene expression-the turning on or off of specific genes-without changing the structure of the genes themselves. Neuroeconomics: exploits new brain-imaging technologies to identify brain regions that are especially active when decisions are being made while playing games, managing resources, making strategic choices, and so on. Early indications are that we possess brain mechanisms dedicated to neuroeconomic evaluations, assessing the relative value of each choice available and then sifting through the evaluated choices in order to make a conscious decision, along with a system that inhibits impulsive decision making. Consciousness: the personal, private awareness of our emotions, intentions, thoughts, and movements and of the sensations that impinge upon us. In an experiment employing somatic intervention we alter a structure or function of the brain or body to see how this alteration changes behavior. In this sort of experiment, the physical alteration is an independent variable, and the behavioral effect is the dependent variable. Control group: In research, a group of individuals that are identical to those in an experimental group in every way except that they do not receive the experimental treatment or manipulation. The experimental group is then compared with the control group to assess the effect of the treatment. In a within-participants experiment, the control group is simply the same individuals, tested before the somatic intervention occurs. An experiment in which the same set of

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individuals is compared before and after an experimental manipulation. The experimental group thus serves as its own control group. In a between-participants experiment, the experimental group of individuals is compared with a different group of individuals who are treated identically in every way except that they don’t receive the somatic intervention. The approach opposite to somatic intervention is behavioral intervention. In this approach the scientist alters or controls the behavior of an organism and looks for resulting changes in body structure or function. The third type of study is correlation, which measures how closely changes in one variable are associated with changes in another variable. Even though correlation cannot establish causality, correlational research can help researchers identify which things are linked, and thus it helps us to develop hypothesis that can be tested experimentally using behavioral and somatic interventions. Reductionism: the scientific strategy of breaking a system down into increasingly smaller parts in order to understand it. Levels of Analysis: The scope of experimental approaches. A scientist may try to understand behavior by monitoring molecules, nerve cells, brain regions, or social environments or using some combination of these levels of analysis. Analysis levels that just simple enough that allow us to make rapid progress on the more complex phenomena under study. Animal research is an essential part of life sciences research, including biological psychology....