Origin of Brain Cells and Brains

The earth formed about 4.5 billion years ago, and the first life forms arose about a billion years later. About 700 million years ago, animals evolved the first brain cells, and, by 250 million years ago, the first brain had evolved. A humanlike brain first developed only about 3 million to 4 million years ago, and our modern human brain has been around for only the past 100,000 to 200,000 years. As evolutionary history goes, that is a short time span. Although life evolved very early in the...

Mental Retardation

Mental retardation, or developmental disability, refers to impairment in cognitive functioning that accompanies abnormal brain development. Impairment may range in severity from mild, allowing an almost normal life style, to severe, requiring constant care. As summarized in Table 6-4, mental retardation can result from chronic malnutrition, genetic abnormalities such as Down's syndrome, hormonal abnormalities, brain injury, or neurological disease. Different causes produce different...

In Review

The neural basis for learning and memory resides at the synapse. Aplysia's synaptic function mediates t wo forms of learning habituation and sensitization. Presynaptic voltage-sensitive calcium channels mediate habituation by growing less sensitive with use. Metabotropic serotonin receptors on a sensory neuron can change the sensitivity of presynaptic potassium channels and so increase Ca2+ influx to mediate sensitization. A t the same time, these receptors can produce fewer or more synapses to...

Linking Brain and Behavioral Development

Scientists thus reason that these two lines of development are closely linked. Events that alter behavioral development should similarly alter the brain's structural development and vice versa. As the brain develops, neurons become more and more intricately connected, and these increasingly complex interconnections underlie increasingly complex behavior. These observations enable neuroscientists to study the relation between brain and behavioral development...

Meningitis and Encephalitis

Various harmful microorganisms can invade the layers of the meninges, particularly the pia mater and the arachnoid layer, as well as the CSF flowing bet ween them, and cause infections called meningitis. One symptom, inflammation, places pressure on the brain. Because the space bet ween meninges and skull is slight, unrelieved pressure can lead to delirium and, if the infection progresses, to drowsiness, stupor, and even coma. Usually, the earliest symptom of meningitis is severe headache and a...

Three Legged Cat Solution

The simplest solution to recovery from brain injury is to compensate in a manner that we call the three-legged cat solution. Cats that lose a leg to accident (and subsequent veterinary treatment) quickly learn to compensate for the missing limb and once again become mobile they can be regarded as having shown recovery of function. The limb is still gone, but the behavior has changed in compensation. A similar explanation can account for many instances of apparent recovery of function after...

Neurotransmission in Four Steps

The four-step process of chemically transmitting information across a synapse is illustrated in Figure 5-3 and explained in this section. In brief, the neurotransmitter must be 1. synthesized and stored in the axon terminal 2. transported to the presynaptic membrane and released in response to an action potential 3. able to activate the receptors on the target cell membrane located on the postsyn-aptic membrane and 4. inactivated or it will continue to work indefinitely.

Figure 219

Diencephalon The connections of only 3 of the 20-odd thalamic nuclei are shown for the right thalamus, but each nucleus connects to a discrete region of cortex. Lying below (hypo) the thalamus, at the base of the brain, the hypothalamus and pituitary lie above the roof of the mouth. The pituitary gland lies adjacent to the optic chiasm, where the left and right optic tracts (originating from the eyes) cross over en route to the occipital lobe. The other principal structure of the diencephalon,...

Sensory Experience and Sensory Reality

Compared with humans, dogs have very limited color vision. Compared with dogs, humans have an olfactory system that smells in black and white. Dogs smell in technicolor. Which sensory system, dog or human, truly represents the world Neither. Human brains and dog brains create species-specific sensations. Each is merely one version of' reality among many. These sensory experiences are not genuine reproductions of the world rather, they exist only in the mind of the perceiver. In fact, the...

The Brains Internal Features

The simplest way to examine the inside of something is to cut it in half. The orientation in which we cut makes a difference in what we see, however. Consider what happens when we slice through a pear. If we cut from side to side, we cut across the core if we cut it from top to bottom, we cut parallel to the core. Our impression of what the inside of a pear looks like is clearly influenced by the way in which we slice it. The same is true of the brain. We can reveal the brain's inner features...

Creating New Information

Figure 2-30 charts a basic example of creating new information in the brain through the sense of vision, beginning with receptor cells, neurons located in the retina of the eye. Different receptor cells are most receptive to light of a particular wavelength red, green, or blue. In the brain, neurons receive inputs from one or more of these color-sensitive receptors. A neuron might be able to receive inputs from only one receptor type, from two receptor types, or from all three. A neuron...

Chromosome Abnormalities

Genetic disorders are not caused only by single defective alleles. Some nervous system disorders are caused by aberrations in a part of a chromosome or even an entire chromosome. Changes in the number of chromosomes, even a doubling of chromosomes is one way in which new species are produced. In humans, one condition due to a change in chromosome number is Down's syndrome, which affects approximately 1 in 700 children. Down's syndrome is usually the result of an extra copy of chromosome 21. One...

Learning Disabilities

Children absorb their society's culture, and acquiring language skills seems virtually automatic for most. Yet some people have lifelong difficulties in mastering language-related tasks, difficulties classified by educators under the umbrella of learning disabilities. Perhaps the most common learning disability is impairment in learning to read, or dyslexia (from the Latin dys, meaning poor, and lexia, meaning reading). Not surprisingly, children with dyslexia have difficulty learning to write...

Action Potentials And Refractory Periods

Although action potentials can occur as many as hundreds of times a second, their frequency has an upper limit. If the axon membrane is stimulated during the depolarizing phase of the action potential, another action potential will not occur. The axon will also not produce another action potential when it is repolarizing, or absolutely refractory. (Exceptions do exist some CNS neurons can discharge again during the repolarizing phase.) If, on the other hand, the axon membrane is stimulated...

The Neural Unit of Thought

What exactly goes on within the brain to produce what we call thinking In the discussion of Alex the parrot, we concluded that thinking must result from the activity of complex neural circuits rather than being the property of some particular region in the brain. One way to identify the role of neural circuits is to consider the responses of individual neurons during cognitive activity. William Newsome and his colleagues (1995) took this approach in training monkeys to identify the presence of...

Autism

Leo Kanner and Hans Asperger first used the term autism (from the Greek autos, meaning self) in the 1940s to describe children who seem to live in their own self-created worlds. Although some of these children were classified as mentally retarded, others' intellectual functioning was preserved. An estimated 1 in 500 people has autism. Although it knows neither racial nor ethnic nor social boundaries, autism is four times as prevalent in boys as in girls. Many autistic children are noticeably...

Animals Engage In Behaviors For Multiple Reasons

One of the most difficult questions to answer is why animals engage in behaviors, especially why they perform particular behaviors at particular times. To address this question, in Chapter 11 we considered the story of Roger, who seemed to have strange, indiscriminate food preferences. We also considered the housefly and learned that what appears to be purposeful behavior is really a response to stimuli coming from its feet and esophagus (Figure E-5). In addition, we examined why cats kill...

Cerebral Palsy

We met Patsy when she took our introductory course on brain and behavior. She walked wi th a peculiar shuff le her handwriting was almost illegible and her speech was at t imes almost unintelligible. Pa tsy had cerebral palsy, and she earned an A in the course. William Little, an English physician, first noticed in 1853 that difficult or abnormal births could lead to later motor difficulties in children. The disorder that Little described was cerebral palsy, although it has also been called...

Spatial Cognition

The location of objects is just one aspect of what we know about space. Spatial cognition refers to a whole range of mental functions that vary from navigational ability (the ability to go from point A to point B) to the mental manipulation of complex visual arrays like those shown in Figure 14-2. Imagine traveling to an unfamiliar park for a walk. As you walk about the park, you need to proceed in an organized, systematic way. You do not want to go around and around in circles. You also need...

Why Study Brain And Behavior

The brain is a physical object, a living tissue, a body organ. Behavior is action, momentarily observable, but fleeting. Brain and behavior differ greatly but are linked. The brain was once thought to play little or no role in behavior, and so the study of brain function was seen as a biological pursuit not central to psychology. Even today, many students view the brain as peripheral to understanding human behavior. W H AT ARE T H E O RIGIN S O F BRA IN A ND BE H AVIO R 3

Neurotransmitter Synthesis And Storage

Neurotransmitters are derived in two general ways. Some are synthesized in the axon terminal from building blocks derived from food. Transporters, protein molecules that pump substances across the cell membrane, absorb the required precursor chemicals from the blood supply. (Sometimes transporter proteins absorb the neurotrans-mitter ready-made.) Mitochondria in the axon terminal provide the energy needed both to synthesize precursor chemicals into the neurotransmitter and to wrap them in...

Seeing Shape

Imagine that we have placed a microelectrode near a neuron somewhere in the visual pathway from retina to cortex and are using that electrode to record changes in the neuron's firing rate. This neuron occasionally fires spontaneously, producing action potentials with each discharge. Let us assume that the neuron discharges, on the average, once every 0.08 second. Each action potential is brief, on the order of 1 millisecond. If we plot action potentials spanning a second, we see only spikes in...

Multiple Intelligences

There have been many other hypotheses of intelligence since Spearman's, but few have considered the brain directly. One exception is a proposal by Howard Gardner, a neu-ropsychologist at Harvard. Gardner (1983) considered the effects of neurological injury on people's behavior. He concluded that there are seven distinctly different forms of intelligence and that each form can be selectively damaged by brain injury. This view that there are multiple kinds of human intelligence should not be...

Neurotransmission in the Autonomic Nervous System

The complementary divisions of the ANS, sympathetic and parasympathetic, regulate the body's internal environment (see Figure 2-29). Recall from Chapter 2 that the sympathetic division rouses the body for action, producing the fight-or-Bight response. Heart rate is turned up, digestive functions are turned down. The parasympathetic division calms the body down, producing an essentially opposite rest-and-digest response. Digestive functions are turned up, heart rate is turned down, and the body...

Modern Tools for Measuring a Neurons Electrical Activity

We do not feel waves of neural activity traveling around our bodies because the waves that carry nervous system messages are very small and are restricted to the surfaces of neurons. Still, we can measure such waves and determine how they are produced, by using electrical-stimulation and -recording techniques. If an electrode connected to a voltmeter is placed on a single axon, the electrode can detect a change in electrical charge on that axon's membrane as the wave passes, as illustrated in...

Inferring Purpose in Behavior To Know a

A pitfall in studying the causes of behavior is to infer purpose from an organism's ac tions. In other words, we have a tendency to assume that behavior is intentional. The problems in making this assumption are illustrated in a wonderful little book titled To Know a Fly, written by Vincent Dethier. When a fly lands on a kitchen table, it wanders about, occasionally stomping its feet. Eventually, it finds a bit of food and sticks its proboscis (a trunklike extension) into the food and eats. The...

Neural Circuit for Explicit Memories

The dramatic amnesic syndrome discovered in H. M. in the 1950s led investigators to focus on the hippocampus, which at the time was regarded as a large brain structure in search of a function. However, because H. M. has damage to other structures, too, the initial view that the hippocampus is the location of explicit-memory processing turned out to be incorrect. It took several decades of anatomical and behavioral studies to sort out the complexities, but, by the mid-1990s, a consensus began to...

Anxiety Disorders

We all experience anxiety at some time, usually acutely as a response to a stressful stimulus or, less commonly, as a chronic reactivity, an increased anxiety response, even to seemingly minor stressors. Anxiety reactions certainly are not pathological and are likely an evolutionary adaptation by which organisms cope with adverse conditions. But anxiety can become pathological to the point of making life miserable. As you discovered in Chapter 11, anxiety disorders are among the most common....

Optical Errors of Refraction and Visual Illuminance

The eye, like a camera, works correctly only when sufficient light passes through the lens and is focused on the receptor surface the retina of the eye or the film in the camera. Too little light entering the eye or the camera produces a problem of visual illuminance it is hard to see any image at all. If the focal point of the light is slightly in front of the receptor surface or slightly behind it, a refractive error causes objects to appear blurry. Refractive errors in the eye are of two...

Functional Asymmetry in the Normal Brain

In the course of studying the auditory capacities of people with temporal-lobe lesions, Doreen Kimura (1967) came upon an unexpected finding in her normal control subjects. She presented people with two strings of digits, one played into each ear, a procedure known as dichotic listening. The subjects' task was to recall as many of the digits as possible. Kimura found that her normal controls recalled more digits presented to the right ear than to the left. This result is a bit surprising...

Light The Stimulus for Vision

Simply put, light is electromagnetic energy that we see. This energy comes either directly from a source, such as a lamp or the sun, that produces it or indirectly after having been reflected off one or more objects. In either case, light energy travels from the outside world, through the pupil, and into the eye, where it strikes a light-sensitive sur face on the back of the eye called the retina. From this stimulation of receptors on the retina, we start the process of creating a visual world....

Birdsong

Of about 8500 living species of birds, about half are considered songbirds. Birdsong has jmany functions, including attracting mates (usually employed by males), demarcating territories, and announcing location or even mere presence. Although all birds of the same species have a similar song, the details of that song vary markedly from region to region, much as dialects of the same human language vary. Figure 9-25 includes sound-wave spectrograms for the songs of male white-crowned sparrows...

The Neural Basis of Drug Cravings

Exposure to drug paraphernalia and other prominent drug-related cues induce intense craving in addicts and thereby influence drug taking. What is the neural basis of this craving Where in the brain does it take place Can craving be prevented or reversed The answers may be found in the brain's mesolimbic dopamine system. Mesolimbic dopamine (DA) neurons are located in the medial part of the midbrain called the ventral tegmental area (VTA), and the axons of these neurons project to a part of the...

Characteristics of Human Thought

Although human cognition is widely believed to have unique characteristics, in what ways, exactly, is it unique Many may answer that human thought is verbal, whereas the thought of other animals is nonverbal. Language is presumed to give humans an edge in thinking, and in some ways it does Language provides the brain with a way to categorize information, allowing us to easily group together objects, actions, and events that have factors in common. Language provides a means of organizing time,...

The Variety of Biological Rhythmns

S winter approaches in Northern latitudes, many Arctic animals prepare their escape. Arctic terns fly 15,000 kilometers to Antarctica, where it is summer. Lemmings, mice, and ground squirrels cannot travel long distances these rodents spend the winter in burrows in a sleeplike state called hibernation. Polar bears, in contrast, congregate to go out onto the pack ice. They migrate toward the Arctic as the days grow ever shorter. Some travel thousands of kilometers. In the continuous darkness of...

Types Of Neurons

The nervous system contains neurons in an array of shapes and sizes, structured differently because of their specialized tasks. Some appear quite simple and others very complex. With a little practice in looking into a microscope, you can quickly learn to recognize three neuron types by their features and functions. Sensory neurons (Figure 3-6A) are designed to bring information into the brain from sensory receptors, interneurons (Figure 3-6B) to process it within the brain, and motor neurons...

Neurochemistry Of

To examine the possible synaptic changes underlying LTP, we turn to the results of some experiments concerning glutamate at the terminals of hippocampal neurons. Glutamate acts on two different types of receptors on the postsynaptic membrane, NMDA (N-methyl-D-aspartate) and AMPA acid) receptors. As Figure 5-20A shows, AMPA receptors ordinarily mediate the responses produced when glutamate is released from a presynaptic membrane. NMDA receptors usually do not respond to glutamate, because their...

The Brains Primary Functions

Perhaps the simplest summary of brain function is that it produces behavior, or movement, as you learned in Chapter 1. To produce behavior as we search, explore, and manipulate our environments, the brain must have information about the world about the objects around us, their size, shape, and movement, for instance. Without H OW D O ES T H E N ERVO U S SYSTE M FUN CTIO N 37 such information, the brain cannot orient and direct the body to produce an appropriate response to stimulation. The need...

Plasticity Hormones Trophic Factors and Drugs

Articles in newspapers and popular magazines often report that drugs can damage your brain. Some drugs certainly do act as toxins and can selectively kill brain regions, but a more realistic mode of action of drugs is to change the brain. Although not many studies have looked at drug-induced morphological changes, there is evidence that some compounds can greatly change the synaptic organization of the brain. These compounds include hormones, neurotrophic factors, and psychoactive drugs. We...

Effects of Damage to the Somatosensory Cortex

Damage to the primary somatosensory cortex impairs the ability to make even simple sensory discriminations and movements. Suzanne Corkin and her coworkers (197Q) demonstrated this effect by examining patients with cortical lesions that included most of areas 3-1-2 in one hemisphere. The researchers mapped the sensory cortices of these patients before they underwent elective surgery for removal of a carefully defined piece of that cortex, including the Suzanne Corkin hand area. The patients'...

Other Kinds of Abnormal Brain Development

The nervous system need not be damaged by external forces to develop abnormally. For instance, many genetic abnormalities are believed to result in abnormalities in the development and, ultimately, the structure of the brain. Spina bifida, a condition in which the genetic blueprint goes awry and the neural tube does not close completely, leads to an incompletely formed spinal cord. After birth, children with spina bifida usually have serious motor problems because of this spinal-cord...

Genotype and Phenotype

The actions of genes give rise to what we call physical or behavioral traits, but these actions are not always straightforward. A gene may be imprinted by one parent so that it is not expressed, even though present. The actions of a protein manufactured by one gene may be suppressed or modified by other genes. Developmental age or experiential factors also may influence gene expression. For these reasons, as well as others, some genes are not expressed as traits or may be expressed only...

The Principle Of Common Descent Results In A Hierarchy Of Complexity In The Evolution Of The Brain

In the evolution of complex nervous systems, simpler and evolutionarily more primi tive forms have not been discarded and replaced but rather have been added to. As a result, all anatomical and functional features of simpler nervous systems are present in the most complex nervous systems, including ours. The bilaterally symmetrical nervous system of simple worms is common to complex nervous systems. Indeed, the spinal cord that constitutes most of the nervous system of the simplest fishes is...

The Neuron Is The Basic Unit Of Anatomy Physiology And Cognition

Basic Nervous System Facts

Neurons are remarkably similar in all species, no matter where they are found in the nervous system. The three basic parts of the neuron are the cell body, the dendrites, and the axon, including the axon terminal, or end foot (Figure E-3). The neuron is the basic unit of information processing, of brain plasticity, and even of cognition. Drugs, for example, act at the level of individual neurons, and individual neurons are what an animal's experiences change. Individual neurons also communicate...

Summary

How can we view the nervous system for functional analysis In contrast with a two-part anatomical organization, the human nervous system can be viewed as composed of three semiautonomous functional divisions. The central nervous system includes the brain and the spinal cord. The somatic nervous system consists of the spinal nerves that enter and leave the spinal column, going to and from muscles, skin, and joints in the body and of the cranial nerves that link the CNS to the head, neck, and...

Gonadal Hormones

We are prepared for our adult reproductive roles by the gonadal hormones that give us our sexual appearance, mold our identity as male or female, and allow us to engage in sex-related behaviors. Sex hormones begin to act on us even before we are born and continue their actions throughout our lives (see Chapters 6, 11, and 13). For males, sex hormones produce the male body and male behaviors. The Y chromosome of males contains a gene called the sex-determining region or SRY gene. If cells in the...

Location in the LGN and Cortical Region Vi

Now consider the connection from the ganglion cells to the lateral geniculate nucleus. In contrast with the retina, the LGN is not a flat sheet rather, it is a three-dimensional structure in the brain. We can compare it to a stack of cards, with each card representing a layer of cells. Topographic Organization of the Visual Cortex (V1) In the right occipital lobe, the area of left central vision (the fovea) is represented at the back of the brain, whereas the more peripheral visual areas are...

Sensory And Motor Divisions In The Brain

Essentially extensions of the spinal cord, the lower brainstem regions hindbrain and midbrain retain the spinal-cord division, with sensory structures located dorsally and motor ones ventrally. Recall that an important function of the midbrain is to orient the body to stimuli. This orientation requires both sensory input and motor output. The midbrain's colliculi, which are located dorsally in the tectum, are the sensory component, whereas the tegmentum, which is ventral (below the colliculi),...

Perception of Sound

The auditory system's task is to convert the physical properties of sound-wave energy into electrochemical neural activity that travels to the brain, which we then perceive as sound. Remember that the waves themselves make no sounds. The sounds that we hear, like the images that we see, are but a product of the brain. To better understand the relation between the energy of sound-wave sensations and sound perceptions, think about what happens when you toss a pebble into a pond Waves of water...

Antidepressants

Drug Effects at D2 Receptors That chlorpromazine can lessen schizophrenia symptoms, whereas the abuse of amphetamine or cocaine can produce them, suggests that excessive activity at the dopamine receptor is related to schizophrenia. Monoamine oxidase (MAO) inhibitor. Antidepressant drug that blocks the enzyme monoamine oxidase from degrading neurotransmitters such as dopamine, noradrenaline and serotonin. Tricyclic antidepressant. Firstgeneration antidepressant drug with a chemical structure...

How Does the Nervous System Respond to Stimulation and Produce Movement

Focus on Comparative Biology Portrait of an Artist The Forebrain and Initiating Movement The Brainstem and Species-Typical Movement The Spinal Cord and Executing Movement Focus on Disorders Spinal-Cord Injury The Motor Cortex Corticospinal Tracts Motor Neurons Control of Muscles The Motor Cortex and Skilled Movements Investigating Neural Control of Skilled Movements Control of Skilled Movements in Nonhuman Species How Motor-Cortex Damage Affects Skilled Movements Left Dr. David Scott Phototake....

The Pain of Rejection

Sorrow, grief, and heartbreak are words that we use to describe a loss. Loss evokes painful feelings, as does the pain inflicted by social exclusion. Exclusion leads to hurt feelings. To discover whether painful or hurtful feelings are manifested in the brain's neural circuitry, Naomi Eisenberger and colleagues (2003) performed an experiment. Participants were scanned in an f MRI apparatus while they played a virtual ball-tossing video game. Initially, the subjects believed that they were...

Biochemical Changes Associated with Schizophrenia

Decreased dopamine metabolites in cerebrospinal fluid Increased striatal D2 receptors Decreased expression of D3 and D4 mRNA in specific cortical regions Increased cortical glutamate receptors Decreased glutamate uptake sites in cingulate cortex Decreased mRNA for the synthesis of GABA in prefrontal cortex Increased GABAA-binding sites in cingulate cortex Source Adapted from The Neurochemistry of Schizophrenia, by W. Byne, E. Kemegther, L. Jones, V. Harouthunian, and K. L. Davis, 1999, in The...

Humans Members of the Primate Order

The human relationship to apes and monkeys places us in the primate order, a subcat-egory of mammals that includes not only apes and monkeys, but lemurs, tarsiers, and marmosets as well (Figure 1-10). In fact, we humans are only 1 of about 275 species in the primate order. Primates have excellent color vision, with the eyes positioned at the front of the face to enhance depth perception, and they use this highly developed sense to deftly guide their hand movements. Female primates usually have...

Pacemaking Circannual Rhythms

The suprachiasmatic nucleus not only controls daily rhythms, it can also control cir cannual rhythms. Russel Reiter (1980) illustrated this form of pacemaking in hamsters. Hamsters are summertime, or long-day, breeders. As the days lengthen in springtime, the gonads of male hamsters grow and release hormones that stimulate the males' sexual behavior. As the days shorten in the winter, the gonads shrink, the amount of the Adapted from The Pineal and Its Hormones in the Control of Reproduction in...

Dominant and Recessive Alleles

If both alleles in a pair of genes are homozygous, the two encode the same protein, but, if the two alleles in a pair are heterozygous, they encode two different proteins. Three possible outcomes attend the heterozygous condition when these proteins express a physical or behavioral trait (1) only the allele from the mother may be expressed (2) only the allele from the father may be expressed or (3) both alleles may be expressed simultaneously. A member of a gene pair that is routinely expressed...

Spinal Cord Injury

Each year, on average, about 11,000 people in the United States and 1000 people in Canada suffer spinal-cord injury. Often the spinal cord is completely severed, leaving the victim with no sensation or movement from the site of the cut downward. Although 12,000 people annually incurring spinal-cord injury may seem like a large number, it is small relative to the number in these two countries who suffer other kinds of nervous system damage each year. Recall from Chapter 1, for example, that...

Potassium Channels Sensitize

The longer-lasting action potential prolongs the inflow of Ca2+ into the membrane. The increased concentration of Ca2+ in turn results in more neurotransmitter being released from the sensory synapse onto the motor neuron that leads to the gill muscle. This increased release of neurotransmitter produces a larger-than-normal gill-withdrawal response. The gill withdrawal may also be enhanced by the fact that the second messenger cAMP may mobilize more synaptic vesicles, making more...

Causes of Abnormal Behavior

Neuroscientists presume that abnormal behavior can result from abnormal brain functioning. Evidence for brain abnormalities is relatively straightforward in neurological disorders, and the causes are largely known, at least in a general sense 1. genetic errors, as in Huntington's disease 2. progressive cell death resulting from a variety of neurodegenerative causes, as in Parkinson's or Alzheimer's disease 3. rapid cell death, such as in stroke or traumatic brain injury 4. loss of neural...

Descartes and Dualism

In the first book on brain and behavior, Treatise on Man, Ren Descartes (1596-1650), a French physiologist, mathematician, and phi' . losopher, proposed a new explanation of behavior in which the brain played an important role. Descartes placed the seat of the mind in the brain and linked the mind to the body. He saw mind and body as separate but interconnected. In the first sentence of Treatise on Man (1664), he stated that mind and body must be joined and united to constitute people To...

Principle 1 Information Processing Sequence in the Brain Is In Integrate

Most neurons have afferent (incoming) connections with tens or sometimes hundreds or thousands of other neurons, as well as efferent (outgoing) connections to neurons and many other cell types, such as muscle cells. The parts of the nervous system make a great many connections with one another. Sensory and motor systems interact con stantly to control the organism's interaction with its environment. The entire brain receives inputs, creates information, and produces behavior, as charted in...

Seeing Color

Scientists have long wondered how people are able to see a world so rich in color. Re call from Chapter 1 the hypothesis that color vision evolved in primates whose diets require them to identify ripe fruits or to avoid predators or other dangers. Another ex planation has its roots in the Renaissance, when painters discovered that they could obtain the entire range of colors in the visual world by mixing only three colors of paint (red, blue, and yellow), the process of subtractive color...

Sleep As a Passive Process

One of the earliest explanations views sleep as a passive process that takes place as a re sult of a decrease in sensory stimulation. According to the theory, as evening ap proaches, there are fewer stimuli to maintain alertness, and so sleep sets in. This theory does not account for the complexity of sleep, nor is it supported by direct experimen tal investigations. It predicts that, if subjects are deprived of all stimulation, they will go to sleep. Recall from Chapter 11, however, that...

NonREM Sleep

Although many people may think that sleep is an inactive period, a remarkable range of activities take place during sleep (see Restless Legs Syndrome). During NREM sleep, body temperature declines, heart rate decreases, blood flow decreases, we perspire and lose body weight owing to water loss, and our levels of growth hormone increase. It was once thought that we do not dream during NREM sleep, but findings from recent studies show that, when subjects are aroused from NREM sleep, they do...

Glial Development

The birth of astrocytes and oligodendrocytes begins after most neurogenesis is complete and continues throughout life. As you know from Chapter 3, oligodendroglia form the myelin that surrounds axons in the spinal cord and brain. Although CNS axons can function before they are myelinated, normal adult function is attained only after myelination is complete. Consequently, myelination is a useful rough index of cerebral maturation. In the early 1920s, Paul Flechsig noticed that myelination of the...

Neurobiology Of Development

Some 2000 years ago, the Roman philosopher Seneca proposed that a human embryo is an adult in miniature, and thus the task of development is simply to grow bigger. This idea, known as preformation, was so appealing that it was widely believed for centuries H OW D O ES T H E BRA IN D EVELO P A ND A DA P T to be true. Even with the development of the microscope, the appeal of preformation proved so strong that biologists claimed to see microscopic horses in horse semen. By the middle of the...

Synchronizing Biorhythms at the Molecular Level

To be effective, a biological clock needs an input signal that tracks light changes during cycles of day and night, the oscillat or f or t imekeeping, and an outpu t signal that can drive slave oscillators. As you know, the inpu t signal is carried by t he retinohypothalamic pathway, which projects from special re tinal receptors through ganglion neurons. These neurons have exci tatory glutaminergic synapses onto t he cells of t he suprachiasmat ic nucleus. In the rodent, this pat hway...

The Hypothalamus the Amygdala and Sexual Behavior

The hypothalamus is the critical structure controlling copulatory behaviors in both males and females. The ventromedial hypothalamus controls the female mating pos ture, which in quadrapedal animals is called lordosis and consists of an arching of the back and an elevation of the rump while the female otherwise remains quite still. Dam age to the VMH abolishes lordosis. The role of the VMH is probably twofold it con trols the neural circuit that produces lordosis, and it influences hormonal...

Neurochemical Correlates Of Schizophrenia

Neuroscientists also consider the neurochemical correlates of brain-behavior relations in schizophrenia. As discussed in Chapter 7, dopamine abnormalities were the first to be linked to schizophrenia, and the fact that most neuroleptic drugs act on the dopamine synapse was taken as evidence that schizophrenia is a disease of ventral tegmental dopamine system. Similarly, drugs that enhance dopaminergic activity, such as amphetamine, can produce psychotic symptoms reminiscent of schizophrenia....

Dorsal Root Ganglion Neurons

The dendrites that carry somatosensory information belong to neurons whose cell bodies are located just outside the spinal cord in dorsal-root ganglia (see Figure 2-28). Their axons enter the spinal cord. As illustrated in Figure 10-17, such a dorsal-root ganglion neuron contains a single long dendrite, only the tip of which is responsive to sensory stimulation. This dendrite is continuous with the somatosensory neuron's axon. Each segment of the spinal cord has one dorsal-root ganglion on each...

Drives and Behavior

Surely stimulating the brain is not the only reason for behavior. Consider the behavior of a typical pet cat living in a house or apartment. It awakes in the morning, stretches, wanders to its feeding place, and has a drink of water and some food. Then it sits and cleans itself. Next, it wanders around and spots its favorite toy mouse, which it pounces on and throws in the air. It may pounce and throw again and again for a number of minutes. Eventually, seemingly bored with the toy, the cat...

The Concept of General Intelligence

In the 1920s, Charles Spearman proposed that, although there may be different kinds of intelligence, there is also some sort of underlying general intelligence, which he called the g factor. Consider for a moment what a general factor in intelligence might mean for the brain. Presumably, brains with high or low g would have some general difference in brain architecture. This difference could not be something as simple as size, because human brain size (which varies from about 1000 to 2000...

Arteriovenous Malformations

An arteriovenous malformation (also called an AV malformation or angioma) is a mass of enlarged and tortuous cortical blood vessels that form congenitally. AV malformations are quite common, accounting for as many as 5 percent of all cases of cerebrovascular disease. Although angiomas may be benign, they often interfere with the functioning of the underlying brain and can produce epileptic seizures. The only treatment is to remove the malformation. This procedure carries significant risk,...

Neural Basis Of Associative Learning

We begin in the forebrain structure called the hippocampus (see Figure 2-20). The lim-bic cortex of the mammalian hippocampus has only three layers, rather than the six layers in the neocortex. The neurons in one of these limbic layers are packed closely together, which aligns their dendrites and cell bodies. This arrangement allows summed EPSPs from many of these neurons sums known as field potentials to be recorded quite easily with extracellular electrodes. Both the relatively simple...

Serotonergic System

The serotonergic system is active in maintaining a waking EEG in the forebrain when we move and thus plays a role in wakefulness, as does the cholinergic system. Serotonin also plays a role in learning, as described in the next section. Some symptoms of depression may be related to decreases in the activity of serotonin neurons, and drugs commonly used to treat depression act on serotonin neurons. Consequently, two forms of depression may exist, one related to norepinephrine and another related...

Intelligence Heredity Environment and the Synapse

Another way of categorizing human intelligence was proposed by Donald Hebb. He, too, thought of people as having two forms of intelligence, which he called intelligence A and intelligence B. Intelligence A refers to innate intellectual potential, which is highly heritable. That is, it has a strong genetic component. Intelligence B is observed intelligence, which is influenced by experience as well as other factors, such as disease, injury, or exposure to environmental toxins, especially in...

Electricalrecording Studies

Another line of evidence that the flow of information in the brain is partly electrical in nature came from the results of recording experiments with the use of a voltmeter, a device that measures the flow and the strength of electrical voltage. As illustrated in Figure 4-2B, the voltmeter has one wire connected to a recording electrode and a second connected to a reference electrode, much as an electrical stimulator does. Any difference in voltage between the tip of the recording electrode and...

Injury to the Visual Pathway Leading to the Cortex

Let us begin by seeing what happens when various parts of the visual pathway leading from the eye to the cortex are injured. For instance, destruction of the retina or optic nerve of one eye produces monocular blindness, the loss of sight in that eye. Partial de struction of the retina or optic nerve produces a partial loss of sight in one eye, with the loss restricted to the region of the visual field that has severed connections to the brain. Injuries to the visual pathway beyond the eye also...

New Circuit Solution

A second way to recover from brain damage is for the brain to change its neural connections to overcome the neural loss. This way is most easily accomplished by processes that are similar to those that we considered for other forms of plasticity. That is, the brain forms new connections that allow it to do more with less. Although this change in the brain would seem to be logical, such changes appear to be fairly small. As a result, there is relatively modest recovery in most instances of brain...

Detecting Location

The fact that each cochlear nerve synapses on both sides of the brain provides mecha nisms for locating the source of a sound. In one mechanism, neurons in the brainstem compute the difference in a sound wave's arrival time at each ear. Such differences in arrival time need not be large to be detected. If two sounds presented through ear phones are separated in time by as little as 10 microseconds, the listener will perceive that a single sound came from the leading ear. This computation of...

Processing Language

More than 4000 human languages are spoken in the world today, and probably many others have gone extinct in past millennia. Researchers have wondered whether the brain has a single system for understanding and producing any language, regardless of' its structure, or whether very different languages, such as English and Japanese, are processed in different ways. To answer this question, it helps to analyze languages to determine just how fundamentally similar they are, despite their obvious...

Myasthenia Gravis

J. was 22 years old in 1941 when she noticed that her eyelid drooped. She consult ed her physician, but he was unable t o explain her condition or give her any help. Over the next f ew years, she experienced some difficul ty in swallowing, general weakness in her limbs, and t errific fatigue. Many of the sympt oms would disappear for days and t hen suddenly reappear. R. J. also not ed that, if she got a good night's sleep, she felt better but, if she performed physical work or became...

The Forebrain and Initiating Movement

Complex movements consist of many components. Take painting a work of art. Your perceptions of what is appearing on the canvas must be closely coordinated with the brush strokes that your hand makes to achieve the desired effect. The same high degree of control is necessary for many other complex behaviors. Consider playing basketball. At every moment, decisions must be made and actions must be performed. Dribble, pass, and shoot are different categories of movement, and each can be carried out...

Development of Problem Solving Ability

The first person to try to identify discrete stages of cognitive development was Swiss psychologist Jean Piaget (1952). He realized that he could infer children's understanding of the world by observing their behavior. For example, a baby who lifts a cloth to retrieve a hidden toy is showing an understanding that objects continue to exist even when out of sight. This understanding, the concept of object permanence, is revealed by the behavior of the infant in the upper photographs of Figure...

Microscopic Inspection Cells and Fibers

Although the parts of a car engine are all large enough to be seen with the naked eye, Corpus callosum. Fiber system the fundamental units of the brain its cells are so small that they can be viewed only connecting the two cerebral hemispheres. with the aid of a microscope. By using a microscope, we quickly discover that the brain has two main types of cells neurons and glia, illustrated in Figure 2-12. The human brain contains about 80 billion neurons and 100 billion glia. Neurons carry out...

Ending a Stress Response

Normally, stress responses are brief. The body mobilizes its resources, deals with the challenge physiologically and behaviorally, and then shuts down the stress response. Just as the brain is responsible for turning on the stress reaction, it is also responsible for turning it off. Consider what can happen if the stress response is not shut down The body continues to mobilize energy at the cost of energy storage. Proteins are used up, resulting in muscle wasting and fatigue. Growth hormone is...

The Autonomic Nervous System

The internal autonomic nervous system (ANS) is a hidden partner in controlling behavior. Even without our conscious awareness, it stays on the job to keep the heart beating, the liver releasing glucose, the pupils of the eyes adjusting to light, and so forth. Without the ANS, which regulates the internal organs and glands by connections through the SNS to the CNS, life would quickly cease. Although it is possible to learn to exert some conscious control over some of these vegetative activities,...

Tourettes Syndrome

The neurological disorder Tourette's syndrome (TS) was first described in 1885 by Georges Gilles de la Tourette, a young French neurologist and friend of Sigmund Freud. Here is how de la Tourette described the symptoms as they appeared in Madame de D., one of his patients Madame de D., presently age 26, at the age of 7 was afflicted by convulsive movements of the hands and arms. These abnormal movements occurred above all when the child tried to write, causing her to crudely reproduce the...

Receptors for Direct and Indirect Effects

Transmitter binds to the binding site. The pore opens, allowing the influx or efflux of ions. Transmitter binds to the binding site. The pore opens, allowing the influx or efflux of ions. Ionotropic Receptor When activated, these embedded proteins bring about direct, rapid changes in membrane voltage. O On your Foundations CD, find the section on the membrane potential in the module on neural communication. Review ionic flow across the cell membrane. Imagine this flow being associated with...

Evolution Of Brain And Behavior

The study of living organisms shows that not all have nervous systems or brains and that nervous systems and behavior built up and changed bit by bit as animals evolved. We will trace the evolution of the human brain and behavior by describing (1) those animals that first developed a nervous system and muscles with which to move and (2) how the nervous system became more complex as the brain evolved to mediate complex behavior. The popular interpretation of human evolution is that we are...

Dendritic Spines Small but Mighty

Dendritic spines, illustrat ed in Experiment 5-4, contain an astounding variety of pro tein molecules. Research now suggests that spines are the paramount example of biological nanotechnology (Tashiro & Yuste, 2003). To mediate learning, each spine must be able to act independently, undergoing changes that its neighbors do not undergo. Spines may appear and disappear on a dendri te in a matter of seconds, and they may even extend or move along a dendrite to search out and contact a...

Evolutionary Development of the Nervous System

The developing brain is less complex than the mature adult brain and provides a clearer picture of its basic structural plan. As detailed in Chapter 7, the biological similarity of embryos of vertebrate species as diverse as amphibians and mammals is striking in the earliest stages of development. The brain of a young vertebrate embryo begins as a sheet of cells that folds into a hollow tube and develops into three regions forebrain, midbrain, and hindbrain. These three regions of the primitive...

Biological Clocks

If the behavior of animals were affected only by seasonal and daily changes, the neural mechanisms that account for changes in behavior would be much simpler to study than they are. Behavior would be driven by external cues, which would be easy to identify, and, accordingly, the neural processes that respond to those cues also would be easy to identify. That behavior is not driven simply by external cues was first recognized in 1729 by French geologist Jean Jacques D'Ortous de Mairan (see...

What Are the Origins of Brain and Behavior

Focus on Disorders Traumatic Brain Injury Focus on Disorders Linking Brain Function to Brain Gross Structure of the Nervous System What Is Behavior Aristotle and Mentalism Descartes and Dualism Focus on New Research The Origins of Spoken Origin of Brain Cells and Brains Classification of Life Evolution of Animals with Nervous Systems The Chordate Nervous System Humans Members of the Primate Order Australopithecus Our Distant Ancestor The First Humans Brain Size and Behavior Why the Hominid...

Sleep As a Biological Adaptation

Another explanation holds that sleep is a biologically adaptive behavior influenced by the many ways in which a species adapts to its environment Sleep is designed as an energy-conserving strategy to cope with times when food is scarce, as you learned in this chapter's first Focus. Each animal species gathers food at optimal times and conserves energy the rest of the time. If the nutrient value of the food that a species eats is high, the species can spend less time foraging and more time...

Structure of the

How do the cells of the retina absorb light energy and initiate the processes leading to vision To answer this question, we first consider the structure of the eye as a whole so that you can understand how it is designed to capture and focus light. Only then do we consider the photoreceptor cells. The functionally distinct parts of the eye are shown in Figure 8-3. They include the sclera, the white part that forms the eyeball the cornea, the eye's clear outer covering Visible Light The part of...

Major Depression

H. was a 53-year-old high school teacher who, although popular with his students, was f eeling less and less sa tisfac-t ion from his work. His marriage was foundering because he was becoming apathetic and no longer wanted to socialize or go on holidays wit h his wi fe. He was having great difficulty getting up in the morning and arriving at school on time. P. H. even tually consulted a physician wi th a complaint of severe chest pains, which he thought signi fied that he was abou t to have...

Graded Potentials

Recall that the charges on the inside and the outside of the cell membrane can change. If the concentration of any of the ions across the cell membrane changes, the membrane voltage will change. The resting potential provides an energy store that can be used somewhat like the water in a dam, where small amounts can be released by opening gates for irrigation or to generate electricity. Conditions under which ion concentrations across the cell membrane change produce graded potentials,...

Principle 7 Brain Systems Are Organized Both Hierarchically and in Parallel

The brain and spinal cord are semiautonomous areas organized into functional levels, and, even within a single level, more than one area may take part in a given function. How then, with these different systems and levels, do we eventually obtain a unified conscious experience Why, when we look at Susan's car, do we not have the sense that one part of the brain is processing features such as shape while another part is processing color Or why, when we tie our shoelaces, are we not aware that...

Auditory Receptors

Hair cells ultimately transform sound waves into neural activity. Figure 9-8 shows the anatomy of the hair cells Figure 9-10 illustrates how they are stimulated by sound waves. The human cochlea has two sets of hair cells 3500 inner hair cells and 12,000 outer hair cells. Only the inner hair cells are the auditory receptors. This frequencies to which the basilar membrane is maximally responsive are mapped as the cochlea uncoils. (B) Sound waves of different frequencies produce maximal...