So if the coffee has 10 teaspoons of sugar in it arthritis diet primal blueprint mobic 7.5mg fast delivery, the person would have to add another 20 percent arthritis bra 15mg mobic overnight delivery, or 2 teaspoons rheumatoid arthritis onset purchase mobic 15 mg with amex, to be able to taste the difference half of the time arthritis medication etodolac discount 7.5 mg mobic overnight delivery. An absolute threshold is the lowest level of stimulation that a person can consciously detect 50 percent of the time the stimulation is present arthritis diet treatment purchase mobic 7.5 mg mastercard. Stimuli that are below the level of conscious awareness are called subliminal stimuli degenerative arthritis in neck symptoms mobic 7.5 mg amex. Many people believe that these stimuli act upon the unconscious mind, influencing behavior in a process called subliminal perception. At one time, many people believed that a market researcher named James Vicary had demonstrated the power of subliminal perception in advertising. It was five years before Vicary finally admitted that he had never conducted a real study (Merikle, 2000; Pratkanis, 1992). Furthermore, many researchers have gathered scientific evidence that subliminal perception does not work in advertising (Bargh et al. However, as in about every other case where subliminal perception has reportedly occurred, these studies use stimuli that are supraliminal-"above the threshold"-and detectable by our sensory systems. However, they are below the level of conscious perception and participants are not aware or conscious that they have been exposed to the stimuli due to masking or manipulation of attention. The real world is full of complex motives that are not as easily influenced as one might think (Pratkanis, 1992). This is called habituation, and it is the way the brain deals with unchanging information from the environment. Sometimes I can smell the odor of the garbage can in the kitchen when I first come home, but after a while the smell seems to go away-is this also habituation? Although different from habituation, sensory adaptation is another process by which constant, unchanging information from the sensory receptors is effectively ignored. In habituation, the sensory receptors are still responding to stimulation but the lower centers of the brain are not sending the signals from those receptors to the cortex. The process of sensory adaptation differs because the receptor cells themselves become less responsive to an unchanging stimulus-garbage odors included-and the receptors no longer send signals to the brain. You might think, then, that if you stare at something long enough, it would also disappear, but the eyes are a little different. Even though the sensory receptors in the back of the eyes adapt to and become less responsive to a constant visual stimulus, under ordinary circumstances the eyes are never entirely still. The smallest difference between two stimuli that can be detected 50 percent of the time it is present is called. When receptor cells for the senses are activated, the process called has begun. While driving down the road looking for the new restaurant you want to try out, not hearing the clicking of the turn signal you forgot to turn off until one of your friends point it out is likely due to : a. Although scientists have long argued over the nature of light, they finally have agreed that light has the properties of both waves and particles. The following section gives a brief history of how scientists have tried to "shed light" on the mystery of light. It was Albert Einstein who first proposed that light is actually tiny "packets" of waves. These "wave packets" are called photons and have specific wavelengths associated with them (Lehnert, 2007; van der Merwe & Garuccio, 1994). When people experience the physical properties of light, they are not really aware of its dual, wavelike and particle-like, nature. With regard to its psychological properties, there are three aspects to our perception White of light: brightness, color, and saturation. We rays will look at this distinction when we 10 10 10 10 10 10 10 10 10 10 10 10 examine perception of color). For example, when a child is using the red paint from a set of poster paints, the paint on the paper will look like a pure red, but if the child mixes in some white paint, the paint will look pink. The hue is still red but it will be less of a saturated red because of the presence of white wavelengths. To see clearly, a single point of light from a source or reflected from an object must travel through the structures of the eye and end up on the retina as a single point. Light bends as it passes through substances of different densities, through a process known as refraction. For example, have you ever looked at a drinking straw in a glass of water through the side of the glass? The structures of the eye play a vital role in both collecting and focusing of light so we can see clearly. The cornea not only protects the eye but also is the structure that focuses most of the light coming into the eye. The cornea has a fixed curvature, like a camera that has no option to adjust the focus. However, this curvature can be changed somewhat through vision-improving techniques that change the shape of the cornea. Pupil Iris opening that changes size depending on the amount of light in the environment 5. Aqueous humor Clear liquid that nourishes the eye Contains photoreceptor cells Light 7. From the pupil, light passes through the lens to the retina, where it is transformed into nerve impulses. The light from the visual image then enters the interior of the eye through a hole, called the pupil, in a round muscle called the iris (the colored part of the eye). The iris can change the size of the pupil, letting more or less light into the eye. Behind the iris, suspended by muscles, is another clear structure called the lens. In a process called visual accommodation, the lens changes its shape from thick to thin, enabling it to focus on objects that are close or far away. The variation in thickness allows the lens to project a sharp image on the retina. People lose this ability as the lens hardens through aging (a disorder called presbyopia). Once past the lens, light passes through a large, open space filled with a clear, jelly-like fluid called the vitreous humor. Ganglion cells Direction of nerve impulses Bipolar neurons Optic nerve fibers going to the brain b. The picture of the cat will disappear at some point because the light from the picture of the cat is falling on your blind spot. But if people stare with one eye at one spot long enough, objects that slowly cross their visual field may at one point disappear briefly because there is a "hole" in the retina-the place where all the axons of those ganglion cells leave the retina to become the optic nerve. You can demonstrate the blind spot for yourself by following the directions in Figure 3. Notice that the message from the temporal half of the left retina goes directly to the left occipital lobe, while the message from the nasal half of the right retina crosses over to the left hemisphere (the optic chiasm is the point of crossover). The optic nerve tissue from both eyes joins together to form the left optic tract before going on to the left occipital lobe. For the left visual field (shown in blue), the messages from both right sides of the retinas will travel along the right optic tract to the right visual cortex in the same manner. Light Right eye travels in a straight line through the cornea and lens; resulting in the image projected on the retina actually being upside down and reversed from left to right as compared to the visual fields. The areas of the retina can be divided into halves, with the halves toward the temples of the Optic tract head referred to as the temporal retinas and the halves toward the center, or nose, called the nasal retinas. Notice that the information from the left visual field (falling on the right side of each retina) goes directly to the right visual cortex, while the information from the right visual field (falling on the left side of each retina) goes directly to the left visual cortex. This is Right visual because the axons from the temporal halves of cortex each retina project to the visual cortex on the same side of the brain while the axons from the nasal halves cross over to the visual cortex on the opposite side of the brain. The rods (about 120 million of them in each eye) are found all over the retina except in the very center, which contains only cones. Rods are sensitive to changes in brightness but not to changes in wavelength, so they see only in black and white and shades of gray. They can be very sensitive because many rods are connected to a single bipolar cell, so that if even only one rod is stimulated by a photon of light, the brain perceives the whole area of those rods as stimulated (because the brain is receiving the message from the single bipolar cell). Because rods are located on the periphery of the retina, they are also responsible for peripheral vision. Because rods work well in low levels of light, they are also the cells that allow the eyes to adapt to low light. Dark adaptation occurs as the eye recovers its ability to see when going from a brightly lit state to a dark state. This is why the bright headlights of an oncoming car can leave a person less able to see for a while after that car has passed. Fortunately, this is usually a temporary condition because the bright light was on so briefly and the rods readapt to the dark night relatively quickly. As people get older this process takes longer, causing many older persons to be less able to see at night and in darkened rooms (Klaver et al. This age-related change can cause night blindness, in which a person has difficulty seeing well enough to drive at night or get around in a darkened room or house. Some research indicates that taking supplements such as vitamin A can reverse or relieve this symptom in some cases (Jacobsen et al. When going from a darkened room to one that is brightly lit, the opposite process occurs. The cones have to adapt to the increased level of light, and they accomplish this light adaptation much more quickly than the rods adapt to darkness-it takes a few seconds at most (Hood, 1998). There are 6 million cones in each eye; of these, 50,000 have a private line to the optic nerve (one bipolar cell for each cone). Cones are located all over the retina but are more concentrated at its very center where there are no rods (the area called the fovea). Cones also need a lot more light to function than the rods do, so cones work best in bright light, which is also when people see things most clearly. Cones are also sensitive to different wavelengths of light, so they are responsible for color vision. While this deer may see quite well when using its rods at night, the bright headlights of a car will activate the cones. Although experts in the visual system have been studying color and its nature for many years, at this point in time there is an ongoing theoretical discussion about the role the cones play in the sensation of color. First proposed by Thomas Young in 1802 and later modified by Hermann von Helmholtz in 1852, this theory proposed three types of cones: red cones, blue cones, and green cones, one for each of the three primary colors of light. Most people probably think that the primary colors are red, yellow, and blue, but these are the primary colors when talking about painting-not when talking about light. Paints reflect light, and the way reflected light mixes is different from the way direct light mixes. For example, if an artist were to blend red, yellow, and blue paints together, the result would be a mess-a black mess. The mixing of paint (reflected light) is subtractive, removing more light as you mix in more colors. As all of the colors are mixed, the more light waves are absorbed and we see black. But if the artist were to blend a red, green, and blue light together by focusing lights of those three colors on one common spot, the result would be white, not black. The mixing of direct light is additive, resulting in lighter colors, more light, and when mixing red, blue, and green, we see white, the reflection of the entire visual spectrum. In the trichromatic theory, different shades of colors correspond to different amounts of light received by each of these three types of cones. It is the combination of cones and the rate at which they are firing that determine the color that will be seen. For example, if the red and green cones are firing in response to a stimulus at fast enough rates, the color the person sees is yellow. If the blue and green cones are firing fast enough, a kind of cyan color (blue-green) appears. In trichromatic theory, the three types of cones combine to form different colors much as these three colored lights combine. They are also the primary colors that are opposites of the colors in the picture and provide evidence for the opponent-process theory of color vision. Brown and Wald (1964) identified three types of cones in the retina, each sensitive to a range of wavelengths, measured in nanometers (nm), and a peak sensitivity that roughly corresponds to three different colors (although hues/colors can vary depending on brightness and saturation). Interestingly, none of the cones identified by Brown and Wald have a peak sensitivity to light where most of us see red (around 630 nm). Keep in mind though, each cone responds to light across a range of wavelengths, not just its wavelength of peak sensitivity. Depending on the intensity of the light, both the medium and long wavelength cones respond to light that appears red. If a person stares at a picture of the American flag for a little while-say, a minute-and then looks away to a blank white wall or sheet of paper, that person will see an afterimage of the flag. Afterimages occur when a visual sensation persists for a brief time even after the original stimulus is removed. The person would also notice rather quickly that the colors of the flag in the afterimage are all wrong-green for red, black for white, and yellow for blue. The phenomenon of the color afterimage is explained by the second theory of color perception, called the opponent-process theory (De Valois & De Valois, 1993; Hurvich & Jameson, 1957), based on an idea first suggested by Edwald Hering in 1874 (Finger, 1994). In opponent-process theory, there are four primary colors: red, green, blue, and yellow. If one member of a pair is strongly stimulated, the other member is inhibited and cannot be working-so there are no reddish-greens or bluish-yellows. From the level of the bipolar and ganglion cells in the retina, all the way through the thalamus, and on to the visual cortical areas in the brain, some neurons (or groups of neurons) are stimulated by light from one part of the visual spectrum and inhibited by light from a different part of the spectrum.
Its accumulation would be dependent only on physical parameters that could be measured socks for arthritic feet cheap mobic 15mg on-line, such as diffusion arthritis in fingers and feet 15 mg mobic with visa, solubility arthritis in back pain buy 15 mg mobic with visa, and perfusion rheumatoid arthritis thyroid purchase 15mg mobic with visa. With this idea in mind arthritis foundation neck exercises generic mobic 15 mg with mastercard, he developed a method to measure the blood flow and metabolism of the human brain as a whole causes of arthritis in back purchase mobic 15mg line. Using more drastic methods in animals (they were decapitated; their brains were then removed and analyzed), Kety was able to measure the blood flow to specific regions of the brain (Landau et al. His animal studies provided evidence that blood flow was related directly to brain function. Computerized Axial Tomography Although blood flow was of interest to those studying brain function, having good anatomical images in order to locate tumors was motivating other developments in instrumentation. Investigators needed to be able to obtain three-dimensional views of the inside of the human body. In the 1930s, Alessandro Vallebona developed tomographic radiography, a technique in which a series of transverse sections are taken. If radioactive forms of oxygen, nitrogen, or carbon could be produced, then they could be injected into the blood circulation and would become incorporated into biologically active molecules. The concentration of the tracers could then be measured over time, allowing inferences about metabolism to be made. In 1950, Gordon Brownell at Harvard University realized that positron decay (of a radioactive tracer) was associated with two gamma particles being emitted at 180 degrees. Using this handy discovery, a simple positron scanner with a pair of sodium iodide detectors was designed and built, and it was scanning patients for brain tumors in a matter of months (Sweet & Brownell, 1953). Kuhl, a radiology resident at the University of Pennsylvania, who had been dabbling with radiation since high school (did his parents know? The problem with most radioactive isotopes of nitrogen, oxygen, carbon, and fluorine is that their halflives are measured in minutes. Anyone who was going to use them had to have their own cyclotron and be ready to roll as the isotopes were created. It happened that Washington University had both a cyclotron that produced radioactive oxygen-15 (15O) and two researchers, Michel Ter-Pogossian and William Powers, who were interested in using it. They found that when injected into the bloodstream, 15O-labeled water could be used to measure blood flow in the brain (Ter-Pogossian & Powers, 1958). His concept was revolutionary, but he could not find any manufacturers willing to capitalize on his idea. Its development is interwoven with that of the radioactive isotopes, aka "tracers," that it employs. Not only were excellent anatomical images produced, but they could be combined with physiology germane to brain function. An increase in oxygen delivery permitted more glucose to be metabolized, and thus more energy would be available for performing the task. In fact, if this proposal were true, then increases in blood flow induced by functional demands should be equivalent to the increase in oxygen consumption. This would mean that the ratio of oxygenated to deoxygenated hemoglobin should stay constant. Instead, Peter Fox and Marc Raichle, at Washington University, found that although functional activity induced increases in blood flow, there was no corresponding increase in oxygen consumption (Fox & Raichle, 1986). In addition, more glucose was being used than would be predicted from the amount of oxygen consumed (Fox et al. Faraday had noted that dried blood was not magnetic and in the margin of his notes had written that he must try fluid blood. They found that indeed oxygenated and deoxygenated hemoglobin behaved very differently in a magnetic field. Deoxygenated hemoglobin is weakly magnetic due to the exposed iron in the hemoglobin molecule. Years later, Kerith Thulborn (1982) remembered and capitalized on this property described by Pauling and Coryell, realizing that it was feasible to measure the state of oxygenation in vivo. Discoveries made independently in 1946 by Felix Bloch at Harvard University and Edward Purcell at Stanford University expanded the understanding of nuclear magnetic resonance to liquids and solids. For example, the protons in a water molecule line up like little bar magnets when placed in a magnetic field. If the equilibrium of these protons is disturbed by zapping them with radio frequency pulses, then a measurable voltage is induced in a receiver coil. He scribbled his ideas on a nearby napkin, and from these humble beginnings he developed the theoretical model that led to the invention of the first magnetic resonance imaging scanner, located at the State University of New York at Stony Brook (Lauterbur, 1973). He later quipped, "You could write the entire history of science in the last 50 years in terms of papers rejected by Science or Nature" [Wade, 2003]). If generalized information about brain function and anatomy were to be obtained, then the scans from different individuals performing the same tasks under the same circumstances had to be comparable. This was proving difficult, however, since no two brains are precisely the same size and shape. Eric Reiman, a psychiatrist working with Raichle, suggested that venous system was visible due to the contrast providaveraging blood flow across subjects might solve this ed by the deoxygenated hemoglobin that was present. The results of this approach were clear and unOn 100 % O2, however, the venous system completely ambiguous (Fox, 1988). This landmark paper presented the first integrated approach for the design, execution, disappeared (Figure 1. This technique led to behavior of a human when a person is lying prone in the development of functional magnetic resonance ima scanner? Throughout this book, we will what to do with them and what their limitations are. The Book in Your Hands 19 draw from the wealth of brain imaging data that has been amassed in the last 30 years in our quest to learn about how the brain enables the mind. Building on this foundation, we launch into the core processes of cognition: hemispheric specialization, sensation and perception, object recognition, attention, the control of action, learning and memory, emotion, and language, devoting a chapter to each. These are followed by chapters on cognition control, social cognition, and a new chapter for this edition on consciousness, free will, and the law. Beginning with Chapter 4, the story is followed by an anatomical orientation highlighting the portions of the brain that we know are involved in these processes, and a description of what a deficit of that process would result in. Next, the heart of the chapter focuses on a discussion of the cognitive process and what is known about how it functions, followed by a summary and suggestions for further reading for those whose curiosity has been aroused. The Book in Your Hands Our goals in this book are to introduce you to the big questions and discussions in cognitive neuroscience and to teach you how to think, ask questions, and approach those questions like a cognitive neuroscientist. In the next chapter, we introduce the biological foundations of the brain by presenting an overview of its cellular mechanisms and neuroanatomy. Phrenologists expanded on this idea and developed a localizationist view of the brain. Patients like those of Broca and Wernicke later supported the importance of specific brain locations on human behavior (like language). At the same time that neuroscientists were researching the brain, psychologists were studying the mind. Out of the philosophical theory of empiricism came the idea of associationism, that any response followed by a reward would be maintained and that these associations were the basis of how the mind learned. Neuroscientists and psychologists both reached the conclusion that there is more to the brain than just the sum of its parts, that the brain must enable the mind-but how? The term cognitive neuroscience was coined in the late 1970s because fields of neuroscience and psychology were once again coming together. Neuroscience was in need of the theories of the psychology of the mind, and psychology was ready for a greater understanding of the working of the brain. The last half of the 20th century saw a blossoming of interdisciplinary research that produced both new approaches and new technologies resulting in noninvasive methods of imaging brain structure, metabolism, and function. Behind the scenes of functional brain imaging: A historical and physiological perspective. No theoretical scientist he, Delgado stepped into the ring in slacks and a pullover sweater while holding a small device in his hand (and a cape, for good effect). The bull slammed on the brakes and the Structure of Neurons skidded to a stop, standing a few feet before the scientist (Figure 2. One odd thing about this bull, however, gave Delgado his confidence: Synaptic Transmission An electric stimulator had been surgically implanted in its caudate nucleus. The Bigger Picture Years before, Delgado had been horrified by the increasingly popular frontal Overview of Nervous System lobotomy surgical procedure that destroyed brain tissue and function. He was Structure interested in finding a more conservative approach to treating mental disorders through electrical stimulation. Using his knowledge of the electrical nature of neuA Guided Tour of the Brain rons, neuroanatomy, and brain function, he designed his devices, the first neural the Cerebral Cortex implants ever to be used. Delgado understood that our nervous system uses electrochemical energy for communication and that nerves can be thought of as glorified electrical cables running to and from our brains. He also understood that inside our brains, neurons form an intricate wiring pattern: An electrical signal initiated at one location could travel to another location to trigger a muscle to contract or initiate a behavior, such as aggression, to arise or cease. Delgado was banking on the hope that he had figured out the correct circuit involved in aggressive behavior. This knowledge is the foundation on which all theories of neuronal signaling are built. Thus, for us, it is important to understand the basic physiology of neurons and the anatomy of the nervous system, which is what this chapter discusses. Finally, we look at the development of the nervous system- prenatally, in the years following birth, and in adults. The Structure of Neurons the nervous system is composed of two main classes of cells: neurons and glial cells. Neurons are the basic signaling units that transmit information throughout the nervous system. Neurons vary in their form, location, and interconnectivity within the nervous system (Figure 2. Glial cells are nonneural cells that serve various functions in the nervous system, some of which are only now being elucidated. These include providing structural support and electrical insulation to neurons, and modulating neuronal activity. We begin with a look at neuronal structure and function, and then we return to glial cells. The standard cellular components found in almost all eukaryotic cells are found in neurons as well. Since all theories of how the brain enables the mind must ultimately mesh with the actual nuts and bolts of the nervous system, we need to understand the basics of its organizational structure, function, and modes of communication. In this chapter, we begin with the anatomy of the neuron and an overview of how information is transferred both within a neuron, and from one neuron to the next. The cell body contains the cellular machinery for the production of proteins and other cellular macromolecules. Like other cells, the neuron contains a nucleus, endoplasmic reticulum, ribosomes, mitochondria, Golgi apparatus, and other intracellular organelles (inset). The dendrites and axon are extensions of the cell membrane and contain cytoplasm continuous with that in the cell body. Cell body Golgi apparatus Ribosomes Axon Axon terminals soma; Greek for "body"), which contains the metabolic machinery that maintains the neuron: a nucleus, endoplasmic reticulum, a cytoskeleton, mitochondria, Golgi apparatus, and other common intracellular organelles (Figure 2. These structures are suspended in cytoplasm, the salty intracellular fluid that is made up of a combination of ions, predominantly ions of potassium, sodium, chloride, and calcium, as well as molecules such as proteins. The neuron, like any other cell, sits in a bath of salty extracellular fluid, which is also made up of a mixture of the same types of ions. Neurons, unlike other cells, possess unique cytological features and physiological properties that enable them to transmit and process information rapidly. The two predominant cellular components unique to neurons are the dendrites and axon. Dendrites are branching extensions of the neuron that receive inputs from other neurons. They take many varied and complex forms, depending on the type and location of the neuron. The arborizations may look like the branches and twigs of an old oak tree, as seen in the complex dendritic structures of the cerebellar Purkinje cells (Figure 2. Each one has a large dendritic tree that is wider in one direction than the other. Many dendrites also have specialized processes called spines, little knobs attached by small necks to the surface of the dendrites, where the dendrites receive inputs from other neurons (Figure 2. Electrical signals travel along the length of the axon to its end, the axon terminals, where the neuron transmits the signal to other neurons or other cell types. Transmission occurs at the synapse, a specialized structure where two neurons come into close contact so that chemical or electrical signals can be passed from one cell to the next. Some axons branch to form axon collaterals that can transmit signals to more than one cell (Figure 2. Later, when we look at how signals move down an axon, we will explore the role of myelin and the nodes of Ranvier in accelerating signal transmission. Neuron has been triple stained to reveal the cell body (blue), dendrites (green), and the spines (red). Neurons communicate with other neurons and cells at specialized structures called synapses, where chemical and electrical signals can be conveyed between neurons. The cell body (far right) gives rise to an axon, which branches forming axon collaterals that can make contact with many different neurons. Information is transferred across synapses from one neuron to the next, or from a neuron to a non-neuronal cell such as those in muscles or glands.
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