Principles of Neurobiology, Second Edition presents the major concepts of neuroscience with an emphasis on how we know what we know. The text is organized around a series of key experiments to illustrate how scientific progress is made and helps upper-level undergraduate and graduate students discover the relevant primary literature. Written by a single author in a clear and consistent writing style, each topic builds in complexity from electrophysiology to molecular genetics to systems level in a highly integrative approach. Students can fully engage with the content via thematically linked chapters and will be able to read the book in its entirety in a semester-long course. Principles of Neurobiology is accompanied by a rich package of online student and instructor resources including animations, figures in PowerPoint, and a Question Bank for adopting instructors.
Frequently asked questions
How do I cancel my subscription?
Simply head over to the account section in settings and click on âCancel Subscriptionâ - itâs as simple as that. After you cancel, your membership will stay active for the remainder of the time youâve paid for. Learn more here.
Can/how do I download books?
At the moment all of our mobile-responsive ePub books are available to download via the app. Most of our PDFs are also available to download and we're working on making the final remaining ones downloadable now. Learn more here.
What is the difference between the pricing plans?
Both plans give you full access to the library and all of Perlegoâs features. The only differences are the price and subscription period: With the annual plan youâll save around 30% compared to 12 months on the monthly plan.
What is Perlego?
We are an online textbook subscription service, where you can get access to an entire online library for less than the price of a single book per month. With over 1 million books across 1000+ topics, weâve got you covered! Learn more here.
Do you support text-to-speech?
Look out for the read-aloud symbol on your next book to see if you can listen to it. The read-aloud tool reads text aloud for you, highlighting the text as it is being read. You can pause it, speed it up and slow it down. Learn more here.
Is Principles of Neurobiology an online PDF/ePUB?
Yes, you can access Principles of Neurobiology by Liqun Luo in PDF and/or ePUB format, as well as other popular books in Biowissenschaften & Neurowissenschaft. We have over one million books available in our catalogue for you to explore.
The brain is a world consisting of a number of unexplored continents and great stretches of unknown territory.
Santiago RamĂłn y Cajal
How does the nervous system control behavior? How do we sense the environment? How does the brain create a representation of the world out of the sensations? How much of our brain function and behavior is shaped by our genes, and how much reflects the environment in which we grew up? How is the brain wired up during development? What changes occur in the brain when we learn something new? How have nervous systems evolved? What goes wrong in brain disorders?
We are about to embark on a journey to explore these questions, which have fascinated humanity for thousands of years. Our ability to address these questions experimentally has greatly expanded in recent years. What we currently know about the answers to these questions comes mostly from findings made in the past 50 years; in the next 50 years, we will likely learn more about the brain and its control of behavior than in all of prior human history. We are at an exciting time as students of neurobiology, and it is my hope that many readers of this book will be at the forefront of groundbreaking discoveries.
PRELUDE: NATURE AND NURTURE IN BRAIN FUNCTION AND BEHAVIOR
As we begin this journey, letâs discuss one of the questions we raised regarding the contributions of genes and environment to our brain function and behavior. We know from experience that both genetic inheritance (nature) and environmental factors (nurture) make important contributions, but how much does each contribute? How do we begin to tackle such a complex question? In scientific research, asking the right questions is often a critical step toward obtaining the right answers. As evolutionary geneticist Theodosius Dobzhansky put it, âThe question about the roles of the genotype and the environment in human development must be posed thus: To what extent are the differences observed among people conditioned by the differences of their genotypes and by the differences between the environments in which people were born, grew and were brought up?â
1.1Human twin studies can reveal the contributions of nature and nurture
Francis Galton first coined the phrase nature versus nurture in the nineteenth century. He also introduced a powerful method for studying this conundrum: statistical analysis of human twins. Identical twins (Figure 1-1), or monozygotic twins, share 100% of their genes in almost all cells, as they are products of the same fertilized egg, or zygote. One can compare specific traits among thousands of pairs of identical twins to see how correlated they are within each pair. For example, if we compare the intelligence quotients (IQs)âan estimate of general intelligenceâof any two random people in the population, the correlation is 0. (Correlation is a statistic of resemblance that ranges from 0, indicating no resemblance, to 1, indicating perfect resemblance.) This correlation is 0.86 for identical twins (Figure 1-2), a striking similarity. However, identical twins also usually grow up in the same environment, so this correlation alone does not help us distinguish between the contributions of genes and the environment.
Fortunately, human populations provide a second group that allows researchers to tease apart the influence of genetic and environmental factors. Nonidentical (fraternal) twins occur more often than identical twins in most human populations. These are called dizygotic twins because they originate from two independent eggs fertilized by two independent sperm. As full siblings, dizygotic twins are 50% identical in their genes according to Mendelâs laws of inheritance. However, like monozygotic twins, dizygotic twins usually share very similar prenatal and postnatal environments. Thus, the differences between traits exhibited by monozygotic and dizygotic twins should result from the differences in 50% of their genes. In our example, the correlation of IQ scores between dizygotic twins is 0.60 (Figure 1-2).
Behavioral geneticists use the term heritability to describe the contribution of genetic differences to trait differences. Heritability is defined as the difference between the correlations of monozygotic and dizygotic twins multiplied by 2 (because the genetic difference is 50% between monozygotic and dizygotic twins). Thus, the heritability of IQ is (0.86 â 0.60) Ă 2 = 0.52. Roughly speaking, then, genetic differences account for about half of the variation in IQ scores within human populations. Traditionally, the non-nature component has been presumed to come from environmental factors. However, âenvironmental factorsâ as calculated in twin studies include all factors not inherited from the parentsâ DNA. These include the postnatal environment, which is what we typically think of as nurture, but also prenatal environment, stochasticity in developmental processes, somatic mutations (alterations in DNA sequences in somatic cells after fertilization), and gene expression changes due to epigenetic modifications. Epigenetic modifications refer to changes made to DNA and chromatin that do not modify DNA sequences but can alter gene expressionâthese include DNA methylation and various modifications of histones, the protein component of chromatin. As we will learn later, all of these factors contribute to nervous system development, function, and behavior.
Twin studies have been used to estimate the heritability of many human traits, ranging from height (~90%) to the chance of developing schizophrenia (60â80%). An important caveat regarding these estimates is that most human traits result from complex interactions between genes and the environment, and heritability itself can change with the environment. Still, twin studies offer valuable insights into the relative contributions of genes and nongenetic factors to many aspects of brain function and dysfunction in a given environment. The completion of the Human Genome Project and the development of tools permitting detailed examination of the genome sequence data, combined with a long history of medical and psychological studies of human subjects, have made our own species the subject of a growing body of neurobiological research (Section 14.5). However, mechanistic understanding of how genes and the environment influence brain development, function, and behavior requires experimental manipulations that often can be carried out only in animal models. The use of vertebrate and invertebrate model species (Sections 14.1â14.4) has yielded much of what we have learned about the brain and behavior. Many principles of neurobiology revealed by experiments on specific model species have turned out to operate in a wide variety of organisms, including humans.
1.2Examples of nature: animals exhibit instinctive behaviors
Animals exhibit remarkable instinctive behaviors that help them find food, avoid danger, seek mates, and nurture their progeny. For example, a baby penguin, directed by its food-seeking instinct, bumps its beak against its parentâs beak to remind its parent to feed it; in response, the parent instinctively releases the food it has foraged from the sea to feed its baby (Figure 1-3).
Instinctive behaviors can be elicited by very specific sensory stimuli. For instance, experimenters have tested the responses of young chicks to an object resembling a bird in flight, with wings placed close to either end of the headâtail axis. When moved in one direction, the object looks like a short-necked, long-tailed hawk; when moved in the other direction, the object looks like a long-necked, short-tailed goose. Seeing the object overhead, a young chick produces different responses depending on the direction in which the object moves, running away when the object resembles a hawk but making no effort to escape when t...