Neuroanatomy Software

Flash Brain Anatomy

This course gives you access to a full online course and software to learn more about the brain than you ever thought possible in a short amount of time. This software contains detailed, 3D brain models, animations to display concepts, hundreds of educational courses, a neuroanatomy atlas, and compatibility with most web browsers. You will also have access to a full online suite of tutors. Neuroanatomy is one of the hardest parts of anatomy to learn, and learning the brain will really be a lot easier if you had a detailed model to base your knowledge off. This software makes the brain as simple as possible, while also giving you a way to learn it throughly. This model simplifies a very complex subject that most people struggle with Don't be one of the people that doesn't know what to do with the brain model! This course is designed to teach you everything about the brain while keeping the lessons manageable and learning at your own pace. More here...

Flash Brain Anatomy Summary

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Flash Brain Anatomy is a professionally made product. Professionally done by acknowledged experts in this area of expertise.

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Human Brain Development Similarities And Differences Between Human And Nonhuman Primates

The observation that the programs that govern development are remarkably conserved throughout phylogeny has led to the wide acceptance that human brain development goes through stages of development similar to those described for nonhuman primates. Whereas the earliest stages of development show limited room for plastic changes, plasticity naturally mediates the later stages of development as early experience in part controls the modulation of the connectivity between neurons. In most species, including humans, the pattern ofconnectivity that emerges as a result of early prenatal stages of development is only a rough sketch of the final wiring. Postnatally, the pattern of connectivity is refined through progressive and regressive events during which axons, dendrites, synapses, and possibly neurons show exuberant growth and major loss, leading to remodeling of the neural circuitry. The extensive changes in connectivity observed during that stage of development are believed to be...

Challenges in Studies of the Postmortem Human Brain

Analyzing the human brain transcriptome and interpreting the outcome of these experiments is a challenging task. Although many of the following considerations are not unique for genomic experiments and apply in general to postmortem brain research, they have a major impact on planning and interpreting the outcome of microarray experiments. Unfortunately, we do not have good strategies to distinguish SNP-driven expression changes from those that are downstream results of SNP-triggered changes or those that arise from epigenetic influences (see later discussion). In addition, no systematic studies of the human brain have addressed the relative frequency of expression changes resulting from SNPs versus epigenetic transcriptome alterations however, studies of transgenic animals clearly suggest that epigenetic and adaptational changes greatly outnumber SNP-driven or gene deletion-induced expression changes (Bunney et al., 2003 D'Agata et al., 2002). In the human brain, we can speculate...

Functional Neuroanatomy of the Brain

Understanding the relationship between brain structure and function, and particularly how this relationship becomes disturbed in the mentally ill, is one of the major challenges to clinical and experimental neuroscientists. The brain may be described in terms of its general structure and key anatomical areas. It may also be described in terms of the cellular or subcellular structure of the different types of cells that constitute the brain. Finally it may be considered in terms of its functional importance in memory, consciousness and control of bodily functions. However the brain is described, each level of organization is essentially linked to another level of organization. Conventionally, neuroscientists have concentrated on the structural aspects of the brain and its cellular components while psychologists and psychiatrists have concentrated on the more functional aspects such as consciousness, thought processing and emotion. With the advent of sophisticated imaging methods and...

Biological Asymmetries In The Human Brain

At first glance, the left and right hemispheres appear to be biologically identical, leading one to wonder why there are so many functional asymmetries. However, postmortem studies of anatomy and structural imaging studies of the living brain have documented a number of consistent physical asymmetries. For example, in the majority of human brains the frontal region is wider and extends farther forward in the right hemisphere and the occipital region is wider and extends farther rearward in the left hemisphere, giving the brain a kind of counterclockwise torque. Because the temporoparietal areas of the left hemisphere are important for language, it may not be surprising that a number of anatomical and cytoarchitectonic hemispheric differences have been found in those areas. For example, consider the Sylvian fissure, which marks the boundary between the frontal and parietal lobes, which lie above the fissure, and the temporal lobe, which lies below the fissure. This fissure tends to be...

Use of human brain tissue in drug discovery

Despite the success in using animal models to develop drugs which have similar pharmacological properties to those drugs in clinical use, they are much less successful in detecting novel compounds that have pharmacological properties, and possible therapeutic indications, that differ from the drugs that are currently available. In an attempt to improve the chance of discovering novel drugs and, at the same time, reduce the cost and increase the number of compounds which may be screened for their potential therapeutic activity, in vitro models have recently been introduced in pharmaceutical and biotechnological companies based on sequences from the human genome. Such an approach has been encouraged by the need to introduce models based on human brain tissue at a much earlier stage in drug development. In support of this view, it has been estimated that man and chimpanzees share more than 98.9 of their genes in common. However, the expression of genes in the brain was more than fivefold...

The development of the human brain in infancy

In comparison with all other mammals the human infant is essentially born too soon in the sense that it is quite helpless for a long time and relies for survival totally on adults for several years. It has been argued that this essentially premature delivery is a consequence of the unusually large size of human brains and heads, if fully developed before birth they would require the mother to have a cervix impossibly wide to support her weight when standing on two legs. The growth and development of the human brain is certainly different from all other animals and this is particularly true for the formation of its higher cognitive abilities such as those which lead to language and conscious thought. An alternative explanation for the birth of a human when its brain is still at an early stage of development, however, might be that experiences and sensations from the external world are essential for it to develop the potential which it has. The human brain may simply be incapable of...

Microarray Analysis of Human Brain Disorders

Transcriptome profiling data obtained from postmortem tissue but cannot replace performing experiments on the diseased human brain the human brain transcriptome is different from the expression pattern seen in the animal brains, including the transcript profile of the nonhuman primates (Caceres et al., 2003). Thanks to the mostly conserved responses to various chemical substances between the human and animal brain tissue, animal model studies of substance abuse and addiction are very informative and greatly outnumber the experiments performed on human brain tissue. Transcriptomic studies in this field are spearheaded by ethanol and cocaine abuse analysis (Ang et al., 2001 Freeman et al., 2001, 2002a,b,c Thibault et al, 2000 Yuferov et al., 2003), both in disease models and on postmortem tissue (Albertson et al., 2003 Lewohl et al., 2000b, 2001). However, the importance of analysis of human postmortem tissue cannot be overestimated the human brain is more complex than the rodent brain...

The human brain and its relationship with flavour

Perhaps the single key realisation that changed the understanding of flavour was when scientists investigating its perception became aware of the then comparatively new field of experimental psychology dealing with the multisensory processing of signals to the brain. Knowledge of the brain and how it processes information has grown dramatically with the development of non-invasive imaging techniques and in particular magneto-encephalography (MEG), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). These techniques allow images of a functioning brain to be created and the last two, in particular, highlight all regions of the brain where neural activity is taking place. The modern concept of the human brain is now one of a hugely interconnected and inherently holistic information processing system and although we have specific areas of the brain that are primarily concerned with a particular task, for example, the processing of vision or hearing, these...

PET Imaging of Labeled Fatty Acid Incorporation into the Human Brain

Positron emission tomography (PET) has been used to quantify local glucose metabolism and blood flow in the human brain and to image brain receptor densities (Rapoport, 1995). However, to date, PET has not been employed successfully in humans to image signal transduction beyond the receptor, the downstream process by which neurotransmitters and drugs are closely linked to cognition and behavior (Cooper et al., 1996). In view of our results on dopaminergic and cholinergic signaling in normal and lesioned rodents (see Section 3.3.), a PET method for in vivo imaging of FA incorporation into the human brain might be of use for examining disrupted signaling in Alzheimer and Parkinson disease.

Neuroanatomy

Of their brain that structurally differ from the neuroanatomy of individuals with no history of mental illness. Furthermore, there is growing evidence that differences in brain structure are also found among individuals with manic-depressive illness and other major diagnostic categories such as major depression and schizophrenia. University of Michigan researchers using positron emission tomography (PET) found that individuals with bipolar illness have a higher density of monoamine-releasing cells than people who do not have an affective disorder. These specialized cells are responsible for controlling the discharge of norepinephrine, serotonin, and dopamine. Magnetic resonance imaging (MRI) studies show that individuals with bipolar disorders have significantly enlarged lateral ventricles, frontal and temporal lobe sulci, and Sylvian fissures. Studies of third ventricular enlargement in bipolar disorders are at best mixed and often contradictory. This appears to be one of the...

Hypothalamic Regulation Of Aggression

Clinical observations in humans suggest a broadly similar role for the hypothalamus in human aggression. Neoplasms that destroy the ventromedial hypo-thalamic area bilaterally are associated with attacks on caregivers reminiscent of animal aggression following ventromedial lesions. In the classic report of Reeves and Plum, a 20-year-old woman developed bulimia and obesity, amenorrhea, diabetes insipidus, and profound behavioral change. Over a 2-year period, she displayed outbursts of aggression characterized by indiscriminately scratching, hitting, or biting examiners who approached. She denied experiencing angry or vindictive internal feelings toward these individuals and expressed surprise and regret regarding her attacks. The outbursts tended to occur more frequently when she had not eaten for several hours, suggesting the emergence of predatory-like aggression. Postmortem examination revealed a hamartoma destroying the ventromedial hypothalamus. In another case report, a patient...

Suggested Reading

J., Morrison, J. H., andConstantinidis, J. (1987). An immunohistochemical study of pro-somatostatin-derived peptides in the human brain. Neuroscience 22, 781-800. Paxinos, G., and Huang, X.-F. (1995). Atlas of the Human Brainstem. Academic Press, San Diego. Tracey, D. J., Paxinos, G., and Stone, J. (1995). Neurotransmitters in the Human Brain. Premium Press, New York.

Homotypical Association Isocortex the Heteromodal and Unimodal Zones

By far the greatest area of the cerebral cortex in the human brain is devoted to six-layered homotypical isocortex (or neocortex), also known as association isocortex. Association isocortex can be subdivided into two major zones modality-specific (unimodal) and high-order (heteromodal). Unimodal sensory association areas are further divided into upstream and downstream components Upstream areas are only one synapse away from the relevant primary sensory area, whereas downstream areas are at a distance of two or more synapses from the corresponding primary area. Unimodal sensory association isocortex is defined by three essential characteristics Some neurons in heteromodal association areas respond to stimulation in more than one modality, indicating the presence of direct multimodal convergence. More commonly, however, there is an admixture of neurons with different preferred modalities. Many neurons have sensory as well as motor contingencies others change firing in ways that are...

Anatomical Changes With

There are essentially two distinct methods that have been used to evaluate brain volumetrics on CT or MRI images. The first involves determining the volumes of specific brain regions by manually tracing their areas on individual slices. The second method uses some type of computer algorithm to segment automatically each image into specific tissue types (e.g., gray matter, white matter, and CSF). Each method has limitations. The trace method is more subjective, although it enables the tracer to make use of his or her knowledge of neuroanatomy. The most precise results are obtained with thin slices, but the analysis can be quite time-consuming. The segmentation method has the advantage of objectivity, but it can be especially susceptible to the partial volume problem Even a single pixel (the smallest element in an image) may contain a mixture of brain tissues, and thus it becomes difficult to categorize every element in the image as belonging to one kind of tissue versus a second. In an...

Anatomy of the Cerebral Venous System 1 General Considerations

From Nolte (1993), The Human Brain An Introduction to Its Functional Anatomy, 3rd ed. Mosby, St. Louis. Used with permission. Figure 4 Circle of Willis. From Nolte (1993), The Human Brain An Introduction to Its Functional Anatomy, 3rd ed. Mosby, St. Louis. Used with permission.

Importance to Theories of Localization and Lateralization

Broca advocated the principle of cerebral localization, which at the time was disputed by more traditional supporters of the concept that the brain acted as a whole. Many scientists agreed that the intellectual activities of the mind resided in the convolutions of the brain and that the most advanced functions were located in the frontal lobes, but they were not ready to locate specific functions in specific convolutions. Broca realized that if articulate language were proven to be located invariably in one place in all human brains, it would be a major step toward proving that all functions were localized. In his presentation of Le-borgne's brain in 1861, he spoke in general on language and localization as an introduction to his clinical and pathological observations (as quoted in Von Bonin, 1960, p. 57)

Anatomy A Gross Morphology

Heschel Convolutions

Encyclopedia of the Human Brain Volume 1 The core auditory region within HG, which in turn may be further subdivided, consists of koniocortex. Its laminar organization is characteristic of primary regions in other modalities it is granular, with a thick, well-defined layer IV containing pyramidal cells. It is also densely myelinated and has high reactivity to cytochrome oxidase and acetylcholinesterase. This area is approximately coextensive with area 41 in Brodmann's cytoarchitectonic map of the human brain and with area TC according to the parcellation of von Economo and Koskinas. It is also sometimes referred to as A1 in the neurophysiological literature. The cytoarchitectonic organization of the rest of the human auditory cortex is not well known, but studies in monkeys have helped to provide a model to which human data may be compared. The core, belt, and parabelt areas mentioned previously have been best defined in the macaque (Fig. 3). In that species the core region may be...

Early Views Of The Organization Of Human Visual Cortex

What Striate Peristriate

Encyclopedia of the Human Brain Volume 1 The location and extent of Brodmann's areas 17,18, and 19 and von Economo and Koskinas' areas OC, OB, and OA are illustrated in lateral and medial views of the human brain in Fig. 2. Similarly, the striate, parastriate, and peristriate subdivisions of occipital cortex, based on the pigmentoarchitectonic of Braak (see later discussion), are illustrated. In the medial view of the hemisphere, Brodmann's area 18 is wider than von Bonin and Koskinas' area OB. Similarly, on the lateral occipital surface, area 18 is described to occupy a b 1 cm wide swath, whereas area OB barely extends onto this surface.

Classical Descriptions A Brocas Cases

Leborgne Brain

Broca's second case was a man named Lelong, who also had lost his ability to use articulate speech but whose aphemia was not complicated by other symptoms. At autopsy, Lelong's lesion proved much more circumscribed than Leborgne's but was also located in the posterior portion of the third frontal convolution. Broca subsequently chronicled 20 more cases in which patients with aphemia had lesions of the third frontal convolution, lending strong support to his hyopthesis originally based on a single case. Collectively, these cases paved the way for the systematic investigation of the functional organization of the human brain based on the analysis of clinical cases. For decades, lesion-deficit analysis was based on postmortem lesion localization. With the advent of X-ray computed tomography (CT) and magnetic resonance imaging (MRI), lesion localization has become premorbid and quantitative (e.g., describing lesion volume as well as location). This work, summarized in Section II, largely...

Anatomical Distribution In The Central Nervous System

Dopamine Synthesis

Pathways in the human brain, almost 90 of catabo-lism in the rat striatum takes place via the monoamine oxidase (MAO) pathway. In the rat, the level of 3,4-dihydroxylphenylacetic acid is thought to reflect catabolism of intraneuronal dopamine, which includes dopamine that is taken back up by the dopamine transporter, whereas 3-methoxytyramine levels are thought to reflect metabolism of extracellular dopa-mine. Cerebrospinal fluid (CSF) levels of homovanillic acid (HVA) are often used as an indicator of dopaminergic activity in humans.

Visceral Representation And Function

Magnetoencephalography Response

Recent evidence has shown for the first time that it is possible to obtain a clear representation of visceral sensation in the human insular cortex similar to that observed in the rodent. fMRI was used to identify regions of the human brain that were activated in response to a series of tests designed to stimulate cardiopulmonary and gustatory receptors. Cardiopul-monary activation included maximal inspiration, Valsalva's maneuver, and maximal handgrip to elevate arterial blood pressure. These maneuvers consistently resulted in discrete changes in activity in the anterior insular cortex, with a time course corresponding to the changes in arterial blood pressure and heart rate they produced (Fig. 7). Gustatory stimuli, such as salt and sucrose perfusion of the tongue, resulted in activation of the inferior anterior insular cortex.

Idiotypic Cortex the Primary Sensory Motor Zones

The visual, auditory, and somatosensory systems provide the major channels of communication with the extrapersonal world. The information transmitted by these channels plays a critical role in shaping the contents of cognition and consciousness. The primary and unimodal areas related to these modalities are cytoarchitectonically highly differentiated and quite large. The vestibular, gustatory, and olfactory sensations do not have the same type of prominence in the primate brain. The corresponding primary areas are cytoarchitectonically less differentiated, smaller, and closer to limbic structures. In the monkey, primary gustatory cortex is located in the frontoinsular junction in BA 43 the primary vestibular area lies within the Sylvian fissure, where the temporal lobe joins the insula and parietal lobe and the primary olfactory cortex is a core limbic region located at the confluence of the insular, orbitofrontal, and temporopolar areas. The equivalent areas of the human brain have...

Anatomic Subdivision Of Cerebellum

Cerebellum Lobes Roman Numerals

Figure 2 Radiological anatomy of the human cerebellum. Magnetic resonance image (T1 weighted) of the human brain and of the cerebellum. Upper part medial view of the brain. White lines indicate planes of sectioning. ABC coronal VIEW of the cerebellum CDE axial VIEW of the cerebellum. Courtesy of Dr. Francesco Tomaiuolo, Clinical and Behavioral Neurology Lab, IRCCS S. Lucia, Rome. Figure 2 Radiological anatomy of the human cerebellum. Magnetic resonance image (T1 weighted) of the human brain and of the cerebellum. Upper part medial view of the brain. White lines indicate planes of sectioning. ABC coronal VIEW of the cerebellum CDE axial VIEW of the cerebellum. Courtesy of Dr. Francesco Tomaiuolo, Clinical and Behavioral Neurology Lab, IRCCS S. Lucia, Rome.

Clinical Evaluation and Management

PET and SPECT provide an alternative method of imaging that assesses cerebral function rather than brain anatomy. In vegetative patients, cerebral blood flow and metabolism are globally depressed. These procedures are useful in examining remaining cortical and brain stem function. In some cases, global reduction of cortical blood flow in the persistent vegetative state appears to be a consistent predictor of poor long-term outcome. Blood flow and metabolic studies can also be used as a diagnostic aide in differentiating individuals in the vegetative state from patients with the locked-in syndrome.

Topography A Sulci Fissures and Lobes

Brain Topography And Function

The two deepest grooves on the brain are known as fissures. The longitudinal fissure separates the right and left cerebral hemispheres, and the transverse fissure separates the cerebral hemispheres from the cerebellum. The smaller and plentiful grooves on the cerebral hemispheres are known as sulci, whereas the folds or ridges of brain between the sulci are called gyri. Some of the sulci and gyri are relatively consistent in all individuals and are used as anatomical landmarks to identify separate regions of the cerebral cortex. The cerebral cortex is divided into five lobes the frontal, parietal, occipital, temporal, and insular lobes. The central sulcus (rolandic sulcus) can be seen on the superior surface of the human brain just slightly behind the midpoint between the anterior and posterior poles. This sulcus then descends inferiorly and anteriorly over the lateral surface of the cerebral hemisphere and separates the frontal and parietal lobes. The central sulcus serves as the...

The Localization Of Function

Stated differently, the functions of the nervous system must be identified on their own terms, which include the processing, storage, and retrieval of information and the organization of behavior. The question then becomes Are some kinds of processes unique to anger (as opposed, for example, to aggression and emotion in general) No simple answer can be given to a question such as this. The human brain is an exceedingly complex organ that has evolved over millions of years. Past adaptations are seldom discarded but instead are maintained and incorporated into newer systems. Thus, some specialization of

Brain Stem Neuronal Organization Including The Reticular Formation

Figure 1 Magnetic resonance image of the sagittal plane of a human brain stem (modified with permission from Blessing, 1997). Figure 1 Magnetic resonance image of the sagittal plane of a human brain stem (modified with permission from Blessing, 1997). Figure 2 A series of photomicrographs of transverse sections through the human brain stem, stained for myelin by the Weil procedure. The insert in each figure gives the approximate level from which the section is taken Aq, aqueduct Arc, arcuate nucleus Coch, cochlear nucleus Cu, cuneate nucleus Cuext, external cuneate nucleus Cun, cuneiform nucleus dmnX, dorsal motor nucleus of the vagus DR, dorsal raphe nucleus Gr, gracile nucleus IC, inferior colliculus icp, inferior cerebellar peduncle Int, nuclues intercalatus IV, trochlear nucleus IX fibers, intramedullary fibers of the glossopharyngeal nerve lat lem, lateral lemniscus LC, locus coeruleus LRN, lateral reticular nucleus LVe, lateral vestibular nucleus mcp, middle cerebellar peduncle...

Neuroanatomical Correlates of Declarative Memory

Amygdala Emotion Star Wars

Figure 6 Lateral surface of the brain. From ''Structure of the Human Brain A Photographic Atlas,'' 3rd ed. by S. J. DeArmond, M. M. Fusco, and M. M. Dewey, copyright 1974, 1976, 1989 by Oxford University Press, Inc. Used by permission of Oxford University Press, Inc. Figure 6 Lateral surface of the brain. From ''Structure of the Human Brain A Photographic Atlas,'' 3rd ed. by S. J. DeArmond, M. M. Fusco, and M. M. Dewey, copyright 1974, 1976, 1989 by Oxford University Press, Inc. Used by permission of Oxford University Press, Inc. Figure 7 Medial surface of the brain. From Structure of the Human Brain A Photographic Atlas,'' 3rd ed. by S. J. DeArmond, M. M. Fusco, and M. M. Dewey, copyright 1974, 1976, 1989 by Oxford University Press, Inc. Used by permission of Oxford University Press, Inc. Figure 7 Medial surface of the brain. From Structure of the Human Brain A Photographic Atlas,'' 3rd ed. by S. J. DeArmond, M. M. Fusco, and M. M. Dewey, copyright 1974, 1976, 1989 by Oxford...

Distributed Largescale Networks And Their Epicenters

Because cortical areas tend to have very extensive corticocortical projections, individual sectors of association cortex are likely to belong to multiple intersecting networks. With rare exceptions, however, thalamic subnuclei have almost no connections among each other and some thalamic subnuclei can project to both epicenters of an individual large-scale neural network. Thalamic subnuclei can thus fulfill the very important role of setting coactivation boundaries for individual networks. Neuroanatomical experiments have shown that interconnected cortical areas are likely to send interdigitating projections to the stria-tum. Since the striatum receives cortical inputs but does not project back to the cerebral cortex, it could serve the role of an efference synchronizer (or filter) for coordinating the outputs of cortical areas in a given network. The human brain contains at least the following five large-scale neurocognitive networks that follow these principles of organization...

Peripheral Nervous System

Nervous System Peripheral Neuropathy

Figure 2 Basic subdivisions of embryonic nervous system at 28 days, prosencephalon (1), mesencephalon (2), rhombencephalon (3). At 42 and 49 days, telencephalon (1a), diencephalon (1b), mesencephalon (2), metencephalon (3a), myelencephalon (3b). From Principles of Neuroanatomy by J. B. Angevine, Jr., and C. W. Cotman, copyright 1981 by Oxford University Press, Inc. Used by permission of Oxford University Press, Inc. (illustration by Steven J. Harrison). Figure 2 Basic subdivisions of embryonic nervous system at 28 days, prosencephalon (1), mesencephalon (2), rhombencephalon (3). At 42 and 49 days, telencephalon (1a), diencephalon (1b), mesencephalon (2), metencephalon (3a), myelencephalon (3b). From Principles of Neuroanatomy by J. B. Angevine, Jr., and C. W. Cotman, copyright 1981 by Oxford University Press, Inc. Used by permission of Oxford University Press, Inc. (illustration by Steven J. Harrison). Figure 3 Brain ventricular system the cerebral hemispheres, diencephalon, midbrain,...

The Diencephalon 1 The Thalamus

Circuitry Motor Cortex

Figure 9 Basal ganglia the massive putamen is continuous medially in many places with the fishlike caudate nucleus and inferiorly with the amygdala. Medial to the putamen and visible only in view c is the cone-shaped globus pallidus with its outer and inner divisions. From Principles of Neuroanatomy by J. B. Angevine, Jr., and C. W. Cotman, copyright 1981 by Oxford University Press Inc. Used by permission of Oxford University Press, Inc. (illustration by Emeline M. Angevine). Figure 9 Basal ganglia the massive putamen is continuous medially in many places with the fishlike caudate nucleus and inferiorly with the amygdala. Medial to the putamen and visible only in view c is the cone-shaped globus pallidus with its outer and inner divisions. From Principles of Neuroanatomy by J. B. Angevine, Jr., and C. W. Cotman, copyright 1981 by Oxford University Press Inc. Used by permission of Oxford University Press, Inc. (illustration by Emeline M. Angevine). Figure 10 Motor system an important...

Nature of the Signals

In sum, MEG detects less brain activity than EEG, and all signals observable with MEG are also seen in EEG, but not vice versa. EEG provides a broader view of neocortical activity that includes both superficial and deep sources at many orientations relative to the scalp. In contrast, MEG reveals a more limited view of brain activity (perhaps half the generators in the human brain), being primarily selective to superficial and tangentially oriented dipoles, and, hence, detecting primarily activity originating in the sulci near the surface. Radial sources are essentially invisible to MEG. However, the electrical currents detected by EEG travel both over the cortex and over the scalp, and they are distorted by their passage through the skull (which has varying thickness at different places). In contrast, MEG is affected by none of these factors.

Intermediary Processing and Transmodal Areas

Unimodal areas contain the initial synaptic relays for the intermediary processing of information emanating from the extrapersonal space. These areas are extremely well developed in the human brain. The absence of interconnections linking a unimodal area in one sensory modality with another in a different modality protects the sensory fidelity of experience and delays cross-modal contamination until further encoding has been accomplished. Unimodal areas are in a position to register the most accurate representation of sensory experience. These areas can encode the perceptual characteristics of specific sensory events, determine if the sensory features of complex entities such as words or faces are identical or not, and even

Brain Lipids during Development

Days after birth in the pig brain, and during the first 8 or 9 months after birth in the human brain (Fig. 4). Moreover, the cells that multiply just before the peak cholesterol synthesis are almost all oligodendroglia, the cells that form myelin around the central neuronal axons. The same sequence of cell (oligodendroglial) multiplication and peak cholesterol accumulation is also seen in the brain of nonmammalian species such as the catfish. Gangliosides are most concentrated in the brain compared to the rest of the body. Within the brain, the concentration in the gray matter is several times higher than that in white matter. Within the gray matter, these lipids are most concentrated in the axon terminals and dendrites, the structures that constitute most of the synaptic interconnections. As mentioned previously, gangliosides are thus considered label lipids for synaptogenesis. Based on ganglioside measurement, it has been shown that the period of most rapid synaptogenesis in the...

Bdv And Human Disease

There are only infrequent reports of isolation of infectious virus from humans, or detection of BDV gene products in human brain by in situ hybridization and immunohistochemistry a group of four North American subjects with temporal sclerosis and a single Japanese subject with schizophrenia. Methods used most commonly for serologic diagnosis of infection include indirect immunofluorescence with infected cells and Western immunoblot or enzyme-linked immunosorbent assays with extracts of infected cells or recombinant proteins. Infection has also been diagnosed through demonstration of BDV transcripts and proteins in tissues or peripheral blood mono-nuclear cells. Frequently, detection of viral RNA has been achieved through nested reverse transcription polymerase chain reaction (nRT-PCR), a sensitive method that is prone to artifacts due to inadvertent introduction of template from laboratory isolates or cross contamination of samples. Amplification products representing bona fide...

The human nervous system is a highly complex assembly of

Nervous tissue that is responsible for a wide range of homeostatic, motor, sensory, cognitive, and emotional functions. Neuroanatomy is the discipline devoted to the structure of the nervous system. Broadly viewed, the nervous system can be divided into several major components (Table I). The first such division is between the central nervous system (CNS), which consists of the brain and spinal cord, and the peripheral nervous system (PNS), made up of numerous spinal and cranial nerves that transmit information to and from the CNS. In this article, we consider the anatomy of the brain, which stands literally and figuratively at the top of the nervous system as the highest integrative organ in the entire body. The cranial nerves, while strictly speaking part of the PNS, will also be included in this account as they are intimately related to brain structure and cannot be omitted in describing its anatomy. This review will necessarily be confined by space limitations to salient features...

Editorial Advisory Board

Damasio, the Van Allen Professor and Head of Neurology at the University of Iowa, and Adjunct Professor at the Salk Institute, has had a major influence on our understanding of the neural basis of decision-making, emotion, language and memory, and consciousness. He elucidates critical problems in the fundamental neuroscience of mind and behavior at the level of large-scale systems in humans, although his investigations have also encompassed parkinsonism and Alzheimer's disease. The laboratories that he and Hanna Damasio (a distinguished neurologist who is independently recognized for her achievements in neuroimaging and neuroanatomy) created at the University of Iowa are a leading center for the investigation of cognition using both the lesion method and functional imaging. Dr. Damasio is a member of the Institute of Medicine of the National Academy of Sciences, a Fellow of the American Academy of Arts and Sciences, a member of the Neurosciences Research Program, a Fellow...

Normal Physiology and Function

In the CNS, oligodendrocytes are responsible for the synthesis and maintenance of the myelin that surrounds the axons of neighboring neurons. The purpose of the myelin sheath is to allow saltatory propagation of nerve impulses along the length of the axon, resulting in a faster and more efficient neural impulse than in uninsulated nerve fibers. The exact cellular mechanisms responsible for the process of myelination are unclear. In humans, oligodendrocytes emerge several days or weeks before they actually start to synthesize myelin, and myelination takes place principally within the first year after birth. Recent studies have shown that initiation of myelination may be partially dependent on the activity of protein kinase C (PKC), a family of phospholipid-dependent enzymes ubiquitously present in the CNS. Not only do myelin-associated proteins appear to be excellent substrates for PKC-mediated phosphorylation but PKC activity also increases gradually after birth, coinciding with the...

Neurochemistry Of Aggression

At least 14 different receptors for serotonin exist in the human brain. Recent investigations ofthe relationship between serotonin and aggression have begun to more precisely dissect serotonergic systems by employing molecular probes of specific serotonergic receptor subtypes. Buspirone, a 5-HT1A agonist, produced a normal prolactin release when given intravenously to healthy male volunteers. This effect was blocked by the nonselective 5-HT receptor antagonist metergoline and by pindolol, a b-adrenergic and 5-HT1 antagonist, in a dose-related fashion. Prolactin response to buspirone was inversely correlated with levels of irritability in patients with personality disorders, suggesting that decreased sensitivity of the 5-HT1A receptor may be responsible for components of impulsive-aggressive behavior in patients with personality disorders.

Brain Structures Involved In Human Classical Conditioning

Although studies of classical conditioning in humans began to wane in the 1960s, particularly for eyeblink classical conditioning, within the past 10 years there has been a resurgence of experimental work that can largely be attributed to the success of classical conditioning as a tool to study brain function in the experimental animal. Currently, our understanding of how different human brain structures contribute to classical condition lags far behind what is known in the animal and will likely never approach the level of precision that is possible with animal studies. Nevertheless, there has recently been much progress with relating classical conditioning to brain function in humans.

Neuronal Degeneration Can Occur As An Apoptosisnecrosis Continuum

This new concept may be important for understanding how neuronal degeneration occurs in neurological disorders that affect the human brain and spinal cord (Table I) and, thus, may be important for future studies aimed at the prevention of neuronal loss in human neurodegenerative diseases. The clarification of the relationships between mechanisms of neuronal death (active or passive) and the resulting structure of dying neurons in human neurodegenerative disease is important, particularly when addressing hypotheses as to whether PCD and apoptosis are equivalent and whether apoptosis and necrosis are mutually exclusive forms of neuronal cell death. Furthermore, if brain maturity dictates how neurons die, then, in humans, neuronal degeneration in adults may be fundamentally different from neuronal degeneration in newborns or children. For example, mature neurons appear to be less capable than immature neurons of displaying an apoptotic structure after an excito-toxic insult. An injury...

Basic Principles And Theoretical Models In Neuropharmacology

Neuropharmacology depends upon many fields for its underlying structural basis. Cellular biology, molecular biology, biochemistry, and branches of neuroscience from neuroanatomy to neurophysiology all have made, and continue to make, substantial contributions to this field. For the sake of simplicity and conceptual economy, we will focus on that small set of models that provides the basic concepts for understanding how diseases develop in the nervous system and how drugs can treat these diseases.

Neuroplasticity in the Aging Brain

Neurotransmitter levels and mechanisms in the aged brain appear to vary from those in young and adult brains in many ways. Implants of young tissue into aged hosts, and those of aged tissue into young hosts, have been studied in order to determine the relative importance of intrinsic versus extrinsic influences in such factors as age-related adrenergic defecits. Receptor plasticity, the up- or downregulation of receptors for specific neuroactive substances, is an important mechanism of neuroplasticity. Many changes in brain function lead to receptor changes since they must result in changes in neurotransmitters and other neuroactive substances. One study of receptor plasticity of the aged human brain demonstrated upregula-tion of dopamine D1 receptors in the brains of three persons, 80, 81, and 87 years of age who had died respectively 9, 19, and 27 days following a unilateral infarct of the ventral midbrain, producing a relative dopamine depletion on the lesioned side. In the autopsy...

Creativity is important and probably vital for innovation

The brain and creativity are typically studied from very different perspectives. Simplifying, the human brain is a topic for the hard sciences, including neurology and medicine. Creativity, on the other hand, is traditionally studied by social and behavioral scientists. This makes it more difficult to bring the two topics together and may explain why there is not more literature on the brain and creativity. Efforts are being made, especially very recently, to bridge the two topics. In fact, researchers are discovering advantages to this kind of cross-disciplinary investigation.

Anatomy of the Hippocampus and Amygdala

As noted earlier, the hippocampus was found to be involved in memory when H.M.'s hippocampi were removed and he exhibited anterograde amnesia. Figure 5 shows a view of the hippocampus and the amygdala using a transparent model of the human brain. The hippocampus was so named because it has a close resemblance to a sea horse ( hippo means horse, and kampos is Greek for sea monster ). The hippocampus is an elaborate infrastructure of computational systems. However, the complex basis on which The hippocampal formation is composed of the hippocampus proper and is formed by layers of neurons that form areas CA1-CA3 (cornu ammonis 1-3), the dentate gyrus, the entorhinal cortex, and the subiculum. The hippocampal formation has an internal circuit known as the trisynaptic circuit. First projection is from the entorhinal cortex to the dentate gyrus. Second, the dentate gyrus neurons give rise to the mossy fibers (axons) that project to CA3 cell fields. Third, the CA3 neurons give rise to the...

Corpus Callosum Labeled

Corpus Callosum And Cerebral Cortex

The corpus callosum is composed of millions of nerve fibers that connect the two halves of the brain. These fibers traveling together from one cerebral hemisphere to the other form a brain structure easily visible to the beginning student of neuroanatomy. Figure 1 shows a saggital section of the brain, which is a slice that runs from front to back on a vertical plane. This slice passes through the midline. The large curved structure in the middle of the brain is the corpus callosum. Although there is considerable variability in the size and shape of the corpus callosum in humans, it is known that it contains approximately 200 million fibers that carry neural signals from one side of the brain to the other. Although most of these fibers are thought to be excitatory, their effect may be inhibitory due to the activity of inhibitory interneurons. Approximately half of these fibers are small and unmye-linated. These fibers transmit information more slowly than the larger myelinated axons,...

Brain Stem Regulation Of Aggression

Figure 1 Critical sites in the hierarchical, multiregional neural system regulating aggression. Portions of the left temporal and orbitofrontal regions are cut away in this midsagittal view of the human brain to optimize visualization. Reproduced with permission from Saver et al., 1996, Neuropsychiatry of aggression. In Neuropsychiatry A Comprehensive Textbook (Fogel, B. S., Schiffer, R. B., Rao, S. M., Eds.) p. 532. Williams & Wilkins, Baltimore . Figure 1 Critical sites in the hierarchical, multiregional neural system regulating aggression. Portions of the left temporal and orbitofrontal regions are cut away in this midsagittal view of the human brain to optimize visualization. Reproduced with permission from Saver et al., 1996, Neuropsychiatry of aggression. In Neuropsychiatry A Comprehensive Textbook (Fogel, B. S., Schiffer, R. B., Rao, S. M., Eds.) p. 532. Williams & Wilkins, Baltimore .

Contribution to Disease

A variety of neurotropic viruses that cause neuro-pathogenesis in the human brain also infect astrocytes. Although in many cases infected astrocytes are not a primary target resulting in neuropathy, they contribute to viral latency and amplification of pathology through the release of cytokines. A good example is human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS). HIV enters the brain and infects microglia and astrocytes, although astrocytic infection is nonproductive. It is hypothesized that astrocytes are a latent reservoir for HIV, complicating the task of complete virus eradication. Astroctyes, in conjunction with microglial cells, contribute to AIDS neuropathy by releasing cytotoxic factors that can amplify the immune response and further contribute to neuronal toxicity.

Dopamine And Neuropsychiatric Disorders

PET enables the direct measurement ofcomponents of dopamine neurotransmission in the living human brain by using radiotracers, which label dopamine receptors, dopamine transporters, and precursors of dopamine or compounds that have specificity for the enzymes that degrade dopamine. Certain types of PET

Neuronal Degeneration in Models of Axotomy and Target Deprivation

Insight into the mechanisms of progressive neuronal degeneration and are relevant to acute and slow, chronic degenerative disorders that affect the human brain or spinal cord (Table VIII). The progression of axotomy-target deprivation-induced neuronal degeneration and the likelihood of subsequent neuronal death or survival are influenced by several variables, including whether the cell body of an axotomized neuron resides within the peripheral nervous system (PNS) or CNS, the age of the animal at the time of injury, the location of axonal trauma in relation to the cell body, and the animal species. In the immature brain and spinal cord, axotomized neurons often die rapidly. Axotomy-induced degeneration of motor neurons in the immature CNS appears to be apoptosis on the basis of structural evidence in mouse and chick and the finding that overexpression of the bcl-2 gene reduces motor neuron death in newborn mice in response to facial nerve transection or sciatic nerve transection. In...

Descriptive Anatomy

Primary Visual Cortex Cytoarchitectonic

Figure 1 Gross anatomy of the occipital lobe in humans and macaque monkeys. Top Medial, ventral, and lateral views of the occipital lobe with medial and lateral views of the whole cerebral cortex (below) from the Visible Man database. Middle Identification of cortical lobes in the macaque monkey. Color code same as for top. Bottom Computer brain model reconstructed from the Talairach and Tournoux Co-Planar Stereotaxic Atlas of the Human Brain showing the standard Talairach coordinate system, with the origin located at the anterior commissure (not shown) and the y axis passing through both the anterior and posterior commissures (not shown). Polarity of axes indicates conventions used in this article. Abbreviations AC-PC, anterior commissure-posterior commissure reference line Cal S, calcarine sulcus POS, parieto-occipital sulcus F, frontal lobe P, parietal lobe T, temporal lobe. (Figures of Visible Man and Macaque monkey brains courtesy of David Van Essen.) Figure 1 Gross anatomy of...

Cerebellar Afferents

Figure 4 Schematic reconstruction of the circuitry of the cerebellar cortex. A single cerebellar folium has been sectioned vertically, both in longitudinal and transverse planes. (Lower left) Enlargement of a single glomerulus (modified with permission from L. Heimer, The Human Brain and Spinal Cord, Fig. 120, p. 213. Copyright 1983 by Springer-Verlag). Figure 4 Schematic reconstruction of the circuitry of the cerebellar cortex. A single cerebellar folium has been sectioned vertically, both in longitudinal and transverse planes. (Lower left) Enlargement of a single glomerulus (modified with permission from L. Heimer, The Human Brain and Spinal Cord, Fig. 120, p. 213. Copyright 1983 by Springer-Verlag).

Functions Of The Basal Ganglia

A related method is to study degenerative diseases of the basal ganglia such as Parkinson's and Huntington's diseases. Although the study of both diseases has provided important insights regarding probable basal ganglia functions, both diseases involve structures outside of the basal ganglia, including those of the cerebral cortex. This phenomenon makes it difficult to isolate basal ganglia functions. Another method of increasing importance in the study of human brain functions is functional neuroimaging, such as positron emission tomography or functional MRI. Functional neuroimaging has the potential to enhance our knowledge of brain systems but also has many drawbacks, including difficulty imaging some types of changes, an inability to readily distinguish inhibitory from excitatory neuronal activity, and the ambiguities almost always present in behavioral designs. Techniques such as surface evoked potentials have been of little value in studying basal ganglia function because of...

Functions Of The Cingulate Cortex A Associative Attention

Figure 6 A three-dimensional and sagittal view of the human brain illustrating the source of error-related negativity (ERN) found after brain electric source analysis of event-related brain potentials. (Bottom) The results of several ERN studies that have demonstrated that the source of the ERN is not affected by response modality (subjects responding with their feet or hands) or error feedback modality (visual, auditory, and somatosensory). Also shown is the ERN source for two reaction time experiments, one involving a decision of whether a number was smaller than larger than'' (RT Exp.1) and another involving a classification of words into semantic categories (RT Exp. 2). Reprinted from Holroyd, C. B.,Dien, J., and Coles, M. G. (1998). Error-related scalp potentials elicited by hand and foot movements Evidence for an output-independent error-processing system in humans. Neurosci. Lett. 242, 65-68, with permission from Elsevier Science . Figure 6 A three-dimensional and sagittal view...

Axonal Pathways Traversing the Brain Stem 1 Descending Pathways

There are other well-recognized descending pathways whose names provide helpful clues to their neuroanatomy. The rubrospinal tract consists of axons of neuronal cell bodies located in the red nuclei in the midbrain. The vestibulospinal tract consists of axons of neuronal cell bodies located in the vestibular nuclei in the dorsolateral part of the rostral medulla ob-longata. Other descending pathways include the so-called reticulospinal tracts. These axons descend in less well-defined pathways. The hypothalamus and certain regions of the pons and medulla contain neurons (presympathetic neurons) whose axons descend to the spinal cord via the dorsolateral funiculi and

Mechanisms of Plastic Changes during Development and Learning

It is commonly believed that they are closely related to synaptogenesis, i.e., the phase of overproduction of synapses observed during cortical development. Studies of nonhuman primate development have indicated that about 35 of axons-neurons are lost from the peak of development to adulthood and that the onset of this loss co-occurs with the period of synaptogenesis. Similar studies conducted on human brain tissue also document periods of overproduction of synapses. Researchers have used electron microscopy to map out the synaptic remodeling that occurs during human development. They have compared synaptogenesis and synapse elimination within several different brain areas. In primary visual cortex, a burst in synaptogenesis occurs at about 3-4 months of age with maximum density reached at 4 months. In contrast, synaptogenesis in the middle prefrontal cortex takes longer, reaching maximum synaptic density at about 3.5 years of age. Furthermore, the same researchers have shown that the...

A LTP or Memory Formation Causes Changes in Gene Expression

Indications so far are that these conditions cause altered expression of a small subset of genes (approximately 12). One possibility is that this altered expression is sufficient to cause profound changes in a complex system such as the brain. Another possibility, which has yet to be examined, is that DNA microarray analysis of a relatively large piece of tissue containing millions of cells misses the changes that occur in a small subset of those cells. After all, neuroanatomy tells us that changes in highly localized nuclei or tracts within the brain will have profound effects. Other molecular biological techniques have been used to examine gene expression in a single cell, and it seems likely that DNA microarray analysis will be adapted to provide the same kind of specificity.

Functional Organization of Primary Auditory Cortex Maps of Stimulus Features

Figure 6 (A and B) Lateral and dorsal views, respectively, of the human brain showing the approximate extent and locations of known auditory fields on the lateral and superior surfaces of the superior temporal gyrus. (C) Diagram of the organization of auditory cortical fields on the same temporal lobe areas of the rhesus monkey (adapted with permission from Hackett, T. A., Stepniewski, I. and Kaas, J. H., J. Comp. Neurol. 394, 475-495, 1998). Figure 6 (A and B) Lateral and dorsal views, respectively, of the human brain showing the approximate extent and locations of known auditory fields on the lateral and superior surfaces of the superior temporal gyrus. (C) Diagram of the organization of auditory cortical fields on the same temporal lobe areas of the rhesus monkey (adapted with permission from Hackett, T. A., Stepniewski, I. and Kaas, J. H., J. Comp. Neurol. 394, 475-495, 1998).

Areas Of Neocortex

Despite the lack of complete knowledge about cortical organization, it seems certain that a major reason that the human brain functions so well is that it has so many cortical areas. Studies of cortical organization in monkeys have given us some clear evidence for how the neocortex is organized in humans, and this evidence has provided some surprises. Most notably, many scientists once thought that most neocortex in humans and monkeys would be devoted to large regions of association cortex'' for associating the information from the different senses. Such large areas would deal with abstractions, so that they would be activated by visual, auditory, or somatosensory events. Thus, most neocortex was considered to be responsive to several senses or multimodal. We now believe that a great deal of the neocortex is devoted to processing information within a sense, and the creation of accurate, modality specific perceptions is not an easy task for the brain. Consider the inaccurate...

Diagnostic Methods A Individual Processes 1 Structural Anatomy

Brain Bleed Scan

Figure 1 X-ray CT. (A) Images of the human brain from an X-ray CT device, demonstrating good anatomical detail, particularly of the skull and ventricular system as well as the subarachnoid CSF spaces. Note that there is less gray-white contrast than in MRI images (Fig. 2A). (B) X-ray CT provided very detailed images of bony structures that surround the central nervous system. This is particularly useful in evaluating pathologic states at the base of the skull, where conventional radiography is often difficult because of patient positioning and the overlap of bony structures in a two-dimensional radiograph. Furthermore, in situations in which trauma is a factor, often patients cannot be manipulated easily because of the possibility of fractures at the base of the skull or in the cervical spine. (C) Intracerebral hemorrhage demonstrated by X-ray CT. Sensitivity for detection of intracranial bleeds is effectively 100 with X-ray CT and it remains the imaging modality of choice in acute...

The Central And Peripheral Systems Mediating Nausea And Emesis

The stimuli influencing the emetic reflex provide important clues as to the brain circuitry mediating nausea and vomiting. Concepts based on results obtained mainly from animals using central and peripheral nerve lesions, from intracerebral injection of drugs into and electrophysiological stimulation from discrete brain regions, and more recently from human brain imaging have begun to establish key structures and pathways. Pharmacology, in discovering new antiemetic treatments, is establishing the relevance of specific neurotransmitters within these pathways.

The Paralimbic Zone Mesocortex

There are five major paralimbic formations in the human brain the orbitofrontal cortex posterior parts of Brodmann's area (BA) 11 and 12 and all of BA 13 the insula (BA 14-16) the temporal pole (BA 38) the parahippocampal cortices, including the pre- and parasubiculum, the entorhinal area, the prorhinal area, and the perirhinal (transentorhinal) area, corresponding to BA 27-28 and 35 and the cingulate complex, including the retrosplenial, ventral cingulate, and subcallosal parolfactory areas, corresponding at least in part to BA 23-26, 29-33.

Morphology and Subtypes 1 Radial Astrocytes

Gfap Staining Human Brain Tissue

Figure 1 Immunohistochemical staining of adult human brain sections for GFAP. Note the radial morphology of the astrocyte tracts toward the outer surface of the brain. The area of intense GFAP staining at the periphery of the section is the glia limitans. Figure 1 Immunohistochemical staining of adult human brain sections for GFAP. Note the radial morphology of the astrocyte tracts toward the outer surface of the brain. The area of intense GFAP staining at the periphery of the section is the glia limitans. Astrocytes have varying morphologies in culture that may not fully reflect the range of morphologies found in the brain. In vitro, astrocytes can be separated from other neural cell types, thereby generating 95-99 astrocyte-enriched cultures. Figure 2 represents the immunofluorescent staining of cultured human astro-cytes. In culture, most astrocytes derived from fetal brain appear fibroblast-like and immunostain with GFAP. These in vitro cultures maintain most of the functional...

Protective Role of Astrocytes

Malignant gliomas are extremely invasive tumors they are the most common type of malignant brain tumors in adults (40 ). Most of them are of astrocytic origin. Despite aggressive treatment assays such as surgery, chemotherapy, and radiotherapy, mean survival rates for this disease are less than 1 or 2 years, depending on the clinical grade of the disease. Gene therapy has been used to kill tumor cells in animal models the classic example of this strategy is the retroviral transfer of the herpes simplex virus thymidine kinase (TK) gene to tumor cells followed by treatment with the antiviral compound gancyclovir to kill cells expressing TK. This strategy was successful in rodents due to the bystander effect, in which cytotoxicity is transferred from cells expressing TK to non-TK-expressing cells. Unfortunately, it did not present any therapeutic effect in humans, presumably because of the low infection rate within human tumors and also because of the dissemination of the tumor cells in...

Neuronal Degeneration in Models of Cerebral Ischemia

Sis in the moth Manduca sexta both occur by PCD however, these cell populations die with distinct structural and biochemical features. Thus, some cells can die by a PCD mechanism that is not associated with the structure of classic apoptosis. Clearly, much more work using animal and cell models is needed to answer this complex question as it may relate to neuronal degeneration in disorders of the human brain and spinal cord.

Structure And Function Of The Central Auditory Pathways

Auditory Pathway

The central auditory pathways have been studied extensively in many primate and nonprimate species using a wide range of anatomical and physiological methods. There are far fewer comparable studies in humans, but from them we may conclude that much of the neural circuitry and many of the neural mechanisms underlying mammalian hearing are, to the first approximation, shared by humans and nonhumans alike. Functional studies of the human central auditory system are discussed later. The top of Fig. 5 is a dorsal view of the human brain stem, midbrain, and thalamus showing the relative positions of the major nuclei in the ascending and descending mammalian auditory system. Auditory cortex on the temporal lobe is shown in cross section. The major connecting pathways are illustrated schematically below. Figure 5 (Top) Dorsal view of the human brain stem, midbrain, thalamus, and cross section of the cortex showing the relative locations of the major nuclei in central auditory pathways....

Quantitative Analysis Living Vertebrates

Invertebrate Mammal Human Brain Size

Darwin could explore the relationship by comparing brain size in wild and domesticated populations of animals known to be related to one another. In what was probably his only contribution to neurobiology, Darwin was the first to observe that the brain in domesticated rabbits was smaller than that in their wild cousins. This is evidently a general principle on the effect of domestication on brain size. It may even be true for human brain evolution if we think of ourselves as domesticated and our ancestors as savage or feral, although the available sample size is too small for a clear test. The earliest Homo sapiens were the neandertals, and they were slightly larger brained, on average, compared to their living conspecifics.

Total Cerebral Volume

A plot of total cerebral volume versus age for 146 healthy boys and girls is presented in Fig. 2. As can be seen, brain sizes are highly variable. This large variability of brain sizes means that a larger number of subjects, or following the same subjects over time, is necessary to discern how brain anatomy changes during adolescence. The relative stability of total brain size throughout childhood and adolescence belies the dynamic activity of the various subcomponents of the brain. In the following sections, the effects of age and gender on these different parts of the brain are examined.

Microglia and Cerebral Ischemia

Figure 4 Microglia and macrophage responses in the human brain 5 days after cerebral ischemia (autopsy case). (A) The infarct is on the left side. Immunocytochemistry for the activation marker MHC class II reveals characteristic morphological changes in microglia from normal brain tissue (right) toward the edge of infarction (left). (B-D) Details of this morphological transformation from the typical ramified microglia (B) to stout microglia with loss of ramification (C) and finally to round phagocytes (D). At the stage of phagocytic transformation within the inner infarct border zone microglia and hematogenous macrophage are indistinguishable. Scale bars 50 mm in A and 25 mm in B-D. Figure 4 Microglia and macrophage responses in the human brain 5 days after cerebral ischemia (autopsy case). (A) The infarct is on the left side. Immunocytochemistry for the activation marker MHC class II reveals characteristic morphological changes in microglia from normal brain tissue (right) toward the...

Memory Function In Normal Aging And Dementia

Human Brain Ageing

Figure 3 (a) MRI image of the human brain showing the location of the hippocampi (arrows) within the medial portions of the temporal lobe. (b) Confocal image of granule cells within the human dentate gyrus (hippocampus). The arrows show the nucleus of a newborn, NeuN immunoreactive, neuron within the adult human brain. Astroglial cells are immunostained for glial fibrillary protein. From Eriksson, P. S., et al. (1998). Neurogenesis in the adult human hippocampus. Nature Med. 4, 1313-1317. (See color insert in Volume 1).

Hypothalamic Organization

Encyclopedia of the Human Brain Volume 2 Figure 1 The disposition of the hypothalamus in relation to other regions of the central nervous system is illustrated in sagittal and ventral exposures of the human brain. In sagittal exposures of the brain the hypothalamus occupies a small region bounded by the anterior commissure (AC), optic chiasm (OC), and mammillary body. Ventral exposure of the brain reveals the three prominent landmarks that define the floor of the hypothalamus the OC rostrally, the infundibular stalk (IS) arising from the tuber cinereum, and the paired spherical protuberances that constitute the MBs. III, third ventricle IV, fourth ventricle. Figure 1 The disposition of the hypothalamus in relation to other regions of the central nervous system is illustrated in sagittal and ventral exposures of the human brain. In sagittal exposures of the brain the hypothalamus occupies a small region bounded by the anterior commissure (AC), optic chiasm (OC), and mammillary body....

Spatial Localization of EEG and MEG

Are necessary to increase the likelihood that the unique solution is indeed also the correct one. Present methods for combining MEG with functional magnetic resonance imaging and structural magnetic resonance imaging can yield high-resolution spatiotemporal maps of human brain activity that are timed to within milliseconds of execution and localized to within millimeters. The combination of methods is a significant step in the direction of the ultimate goal of neuroimaging, as noted earlier.

Cortical Eye Fields and Saccades

Parietal Eye Field

Figure 14 Cortex for eye movements in man and monkey. Cortical regions important for saccade and smooth-pursuit eye movements are highlighted on lateral views of a monkey brain (top) and human brain (bottom). In both monkey and man, FEF is in front of premotor cortex for the hand and neck and mostly lies within the sulcus marking the anterior limit of the precentral gyrus. In both species, the smooth-pursuit region of FEF is just posterior to the saccadic region of FEF. A dorsolateral view is used for the monkey brain in order to minimize distortion of the frontal lobe sulci. Figure 14 Cortex for eye movements in man and monkey. Cortical regions important for saccade and smooth-pursuit eye movements are highlighted on lateral views of a monkey brain (top) and human brain (bottom). In both monkey and man, FEF is in front of premotor cortex for the hand and neck and mostly lies within the sulcus marking the anterior limit of the precentral gyrus. In both species, the smooth-pursuit...

Motor Memory A Implicit and Explicit Memory Systems

The distinction between an explicit memory system, which depends on the MTL, and an implicit motor memory system has several implications for motor control in the human brain. Voluntary actions have been defined as those that are learned, attended, and based on a comparison among alternatives. This awareness depends on the explicit memory system. Other actions, including but by no means limited to reflex movements, proceed without conscious awareness. Some subconscious movements bear obvious markings of this unawareness, such as the stretch reflex or the vestibuloocular reflex (VOR). The latter serves as a case in point. When people move their head left while looking at something, their eyes move equally fast and equally far in the opposite direction. They are probably aware of the object at the focus of attention. However, they cannot report anything about the motor memory that allows them to keep looking directly at that object, regardless of their head movements. Adjusting the VOR...

Neural Circuitry of Voluntary Saccades

The principal eye movement of the FS is the voluntary saccade. Humans average about two saccades sec while awake, and thus most of the day is spent in brief fixations of different parts of the visual world, continually interrupted by saccades. This incessant visuomotor activity, the processing of foveal visual data during a fixation, as well as the planning and execution of the next saccade, occupies much of the human brain, as exemplified by the expansive zones of

Olivocochlear Efferent System Central Modulation of Inner Ear Transduction

The MOC arises for the most part from neurons medial to the MSO and reaches the base of outer hair cells mainly in the contralateral inner ear. Collaterals of olivocochlear axons terminate in the cochlear nuclei. Both LOC and MOC neurons receive input from the ventral cochlear nucleus, with the MOC also receiving input from the inferior colliculus. Cochlear efferents are activated by sound and thereby provide reflex feedback to the cochlea. The consequence of this feedback is increased acoustic threshold due to reduced OHC amplification, which helps protect the cochlea from potentially damaging loud sounds and improves detectability of wanted sound in the presence of unwanted background masking noise. Sound induced reflex contraction of the middle ear muscles serves to complement the action of the olivocochlear system.

Investigating The Aging Brain

Four fundamental problems make the investigation of the senescent human brain complex. First, how should one study aging Comparing a group of young versus a group of old subjects (i.e., a cross-sectional design) has numerous disadvantages, including that one is not studying the aging of any single subject, and the results can be compromised by secular effects. For example, the young subjects of today grew up in a world of better health care than did the old subjects. They may be physically larger, may have engaged in Encyclopedia of the Human Brain Volume 1

Historical Development

Clinical neuropsychology traces its roots to the confluence of three major tributaries of psychological science psychophysics, the psychometric method, and the lesion method in behavioral neuroanatomy. New methodologies for viewing the brain, both structurally and functionally, continue to illuminate the everyday miracles of thought, memory, and emotion. The integration of clinical work with experimental discoveries has reached a new zenith in cross-fertilization of both endeavors. The phenomenal growth of clinical neuropsychology over the past three decades owes much to contemporaneous work in clinical neuroscience.

Locus Ceruleus Efferent Fibers Innervate Many Target Structures

Cleos Meynert

Figure 1 Noradrenergic pathways in the human brain. Sagittal human brain section containing the main projection sites of noradrenergic neurons. A6 Noradrenergic nucleus corresponding to the locus ceruleus. It widely projects to the anterior part of the brain and also to the cerebellum and spinal cord. A1-A2 Medullary noradrenergic nuclei, projecting essentially to the hippocampus, thalamus, and hypothalamus. Figure 1 Noradrenergic pathways in the human brain. Sagittal human brain section containing the main projection sites of noradrenergic neurons. A6 Noradrenergic nucleus corresponding to the locus ceruleus. It widely projects to the anterior part of the brain and also to the cerebellum and spinal cord. A1-A2 Medullary noradrenergic nuclei, projecting essentially to the hippocampus, thalamus, and hypothalamus.

Human Nervous System Preface

The functions of the human brain are the last major challenge to science. Despite having made rapid strides in understanding the cosmos, subatomic particles, molecular biology, and genetics, we still know very little about the organ that made these discoveries possible. How does the activity of 100 billion nerve cells mere wisps of protoplasm that constitute the brain give rise to the broad spectrum of abilities that we call consciousness, mind, and human nature There is now, more than ever before, a real need for a standard reference source covering all aspects of the human brain and nervous system, and the Encyclopedia of the Human Brain is the most up-to-date and comprehensive coverage to date. It is a compendium of articles contributed by many of the world's leading experts in neuroscience and psychology. These essays will be of interest to a wide range of individuals in the behavioral and health sciences. Written in an engaging, accessible style, the encyclopedia not only is an...

Studies Of Multisensory Integration In Human Cortex

ERP studies have also identified presumptive poly-sensory cortices in humans. The changes in human brain activity that are induced by multisensory stimuli have also been associated with an increased response accuracy and reaction speed to these stimuli. Unfortunately, the spatial resolution of the ERP technique is not sufficient to allow researchers to identify the specific sulci and gyri that are involved in these processes. It is in specifying the locus of evoked activity in the human brain that functional imaging techniques have had their greatest impact, because they have centimeter or subcentimeter resolution. Two imaging techniques, both of which utilize changes in cerebral blood flow to assess neural activity, have become quite popular in studies of multisensory integration positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). These techniques have confirmed the ERP observation that the activity in primary visual and auditory cortices can be...

Plasticity in Response to Music Perception

As this article makes clear, music, even when only perceived, engages and activates the human brain at many levels auditory, cognitive, emotional, and, when working memory or imagery are involved, motoric. Across a lifetime of exposure, musical experience, both active and passive, has the potential to leave lasting traces in our brains, not only through the formation of memories for specific musical sounds and gestures (a musical lexicon ) but also in more general ways. Like language, music is an accumulated product of humankind that is continually being passed on and added to. Questions regarding how (and why) the human brain produces and responds to music will continue to occupy researchers and philosophers for many years to come and touch upon many of the brain's most complex and integrative abilities.

Emotional Affect versus Cognitive Processing Load

Subjects were required to classify stimuli along an emotional scale as neutral, positive, or negative. The stimuli were individual words (e.g., calm, delighted, and insecure ) intermixed with individual pictures of human faces (Fig. 6, top). There is ample evidence, both from the domain of human functional neuroimaging and from the literature of human brain lesions, that words and faces are exceptionally good stimuli for the activation of specific brain regions. Pictures of faces are good stimuli to activate the fusiform gyrus, especially on the right side. Single words, when associated with a semantic (rather than a purely perceptual) task, are effective stimuli for activating the inferior frontal region, almost always most strongly on the left side. One might reasonably

Cortical Signs Of Mental Workload

The EEG data provide good evidence for a physiological basis for resources in the human brain. The changes in EEG a and 0 may represent a relatively gross, whole-task allocation of resources, given that the associated brain electrical activity spans several seconds and is relatively invariant with the type of information processing (although hemispheric differences have been noted with different forms of processing, e.g., verbal versus spatial tasks). The processing characteristics of specific components underlying a task can be assessed by recording task-evoked ERPs, which reflect the neural activity in response to a stimulus with millisecond precision.

The Acting And Perceiving Hand

Many of our cultural and technological achievements that mark us as human depend on skilled use of the hand. We use of our hands to gesture and communicate, make and use tools, write, paint, play music, and make love. Thus, the human hand is a powerful tool through which the human brain interacts with the world. We use our hands both to perceive the world within our reach (haptic perception) and to act on this world. These two functions of the hand, which are largely accomplished by touching and manipulating objects in our environment, are intimately related in terms of sensorimotor control. Haptic perception requires specific hand movements that are tailored to the kinds of information the perceiver wishes to extract. For example, to obtain information about the texture of an object, people rub their fingertips across the object's surface, and to obtain information about shape they trace the contour of the object with their fingertips. Conversely, in object manipulation sensory and...

Cerebral White Matter

The human brain is that portion of the central nervous system within the cranium. Twelve pairs of cranial nerves provide conduits for special senses, general sensation, and motor function, mainly for the head and neck. The brain is continuous caudally with the spinal cord, which in turn is connected to numerous peripheral nerves that travel to and from the entire body. Thus, the brain, at the highest level of the nervous system both literally and figuratively, exerts control over all aspects of bodily function. The brain is best known for its gray matter the neocortex and a variety of subcortical structures but white matter also forms a considerable portion of the brain and has an important role in many of its operations. The white matter of the cerebrum those fibers and tracts that are found within and between the paired cerebral hemispheres serves to connect various gray matter regions into functionally unified neural networks. The Encyclopedia of the Human Brain Volume 1

Consciousness Mind And The Dual Brain

The dual nature of the human brain has led to interesting discussion of the implications for consciousness and mind. Among other things, the discovery that both of the disconnected hemispheres of split-brain patients have a good deal of competence with respect to perception and motor control has led to speculation about whether or not the surgery has produced a doubling of consciousness or resulted in people with two minds. The neurobiologist Roger Sperry, who won the Nobel prize for his work with these patients, believed that this was the case. In part, he based his conclusion on the fact that the disconnected right hemisphere has its own perceptions, cognitions, and memories of which the disconnected left hemisphere is completely unaware. Others, however, have questioned whether the right hemisphere can truly think and whether its limited abilities include the same level of awareness and consciousness that seems typical of the left hemisphere. Certainly, the disconnected right...

Growth of Different Cell Types

While studying the cellular growth of the human brain, Dobbing and Sands observed two distinct peaks of DNA accumulation in the forebrain, the first occurring at 18 weeks of gestation and the second at approximately birth (Fig. 6). The first peak was interpreted as corresponding to the peak of neuronal multiplication and the second to that of glial multiplication. However, it is likely that the adult neuronal population is not achieved at 18 weeks of fetal life some neurons continue to divide beyond this time, but their number is not significant compared to the number achieved by 18 weeks of gestation. Man is thus a fortuitous species in that his brain neuronal population is established as early as mid-fetal life and

The corpus callosum is one of the most anatomically

Prominent structures in the human brain. It is composed of approximately 200 million fibers that course across the brain's midline to connect the two cerebral hemispheres. Despite its structural prominence, which led early investigators to believe it played an important role in cognition and behavior, identifying the role of callosal connections in modifying behavior has proven difficult. This article discusses the anatomy of the callosum, the changing view of its role in behavior, the effects of surgical and other lesions on different aspects of behavior, studies of callosal transfer times, and theories of the role of the callosum in human laterality, cognition, and consciousness.

Experimental Design

Designing experiments for fMRI-based studies presents unique opportunities and challenges. First, fMRI like position emission tomography (PET) using O15 depends on the indirect signals generated by hemody-namic changes (i.e., changes in blood flow and or blood chemistry) rather than the more direct electrochemical changes associated with neural activity. Second, there are numerous technical challenges that follow from the particular physics of MRI when used for high-speed imaging of the human brain. Third, there are a number of practical considerations associated with both safety and the physical requirement for minimum movement of the subjects in fMRI studies that add to the challenges of fMRI experimental design. All these factors affect (and, in turn, are affected by) the current practical and future potential limits of spatial and temporal resolution associated with fMRI. Finally, as with any experimental approach to important questions concerning human psychology, the most...

Structural Equivalence

For those researchers of AI who do claim some measure of structural validity to their work, two levels of structure and mechanisms may usefully be distinguished the cognitive level and the level of brain anatomy. At the cognitive level, the psychologist posits structures and mechanisms to account for the observed behavior, and although these objects may have no clear implementation in terms of brain anatomy, it is a requirement that such a mapping could be plausibly found. The other level of structure is that of brain anatomy the structures and mechanisms that can be physically observed, probed, and generally examined. At the cognitive level, we deal with abstract structures such as short-term memory and mechanisms such as forgetting caused by attention shift. At the physical level the structures may be an observed pattern of interconnectivity ofneurons, and the mechanisms may be pulse frequency between the component neurons. Neither level is simple, nor are they always distinct, but...

Plasma Catecholamines

The three catecholamines, when found intact in plasma, do not come from the brain because they cannot cross the blood-brain barrier however, their metabolites can. Thus, metabolites in plasma originate both in brain and in peripheral tissues. Study of these metabolites has provided insight into the role that catecholamines play in behavior. However, direct study of catecholamines in living human brain tissue has not been possible. Fortunately, imaging technologies such as positron emission tomography (PET), magnetic resonance imaging, and single positron emission computerized tomography open up possibilities for visualizing catecholaminergic function in live conscious human subjects during waking hours. In addition, some of these imaging techniques can quantify neurotransmitter receptors and identify concentration differences at the synaptic level following psychopharmacologic administration. A variety of methods are available for measuring catecholamines in plasma.

Contrast in an Image

In the earliest fMRI studies, exogenous contrasts (chemicals injected into the bloodstream of the subject) were used to obtain contrast. These blood-borne chemicals locally distorted the magnetic field, thus allowing increased blood perfusion to be detected. Subsequent studies demonstrated that endogenous contrast agents (i.e., naturally occurring molecules in the body, such as the concentration of deoxyhemoglo-bin in the blood) could also yield sufficient contrast between different states of neural activity. The use of endogenous contrast agents obviated the need for injecting foreign molecules into the bodies of normal (healthy) subjects, and this is one of the key reasons that fMRI has become so popular as a technique for assessing human brain function. In the short history of fMRI, a wide variety of techniques that produce various contrasts have been developed for detecting changes in brain physiology.

Vision and Perception

Sight, although not essential, appears to be an important component of human intelligence. AI vision systems have many potential applications, from automated security camera systems to automatic detection of pathological images in medicine. Because of the accessibility (and assurance of general functional commitment) of the optic tract, mammalian visual systems offer some of the best opportunities for basing AI systems on neuroanatomical data rather than cognitive-level abstractions. Figure 2 is one example of an attempt to build an AI vision system with regard to neuroanatomy.

Training Requirements

PhD or MD degree and extensive neurofeedback training and experience required for the highest level. Opponents of higher standards sometimes note that undesirable side effects of NF are rare and that, although it may seem incredible (and threatening to established health care professionals), training beyond the bachelor's degree level is not necessary to practice the art of NF and higher standards would be unfair to lesser educated practitioners and to the many persons in need of NF treatment. Although most, if not all, groups currently providing NF training limit enrollment to those with master's level or higher degrees, the field has an unusually diverse group of professionals, including physicians, professional counselors, psychologists, physical therapists, chiropractors, social workers, and nurses. Whereas NF may be a very safe procedure and it may not be essential that its practitioners be knowledgeable about details of EEG dynamics, neuroanatomy, or psychiatric diagnoses,...

Neuroimaging Studies

A small number of studies have used invasive techniques to study anterior cingulate function in humans, recording from or stimulating cingulate neurons during neurosurgery. Stimulation in ventral-rostral areas has been found to evoke autonomic changes in blood pressure and heart rate, visceromotor responses including salivation and vomiting, emotional responses including fear, agitation, and euphoria, and vocalizations with affective content. Anterior cingu-late stimulation has also been shown to evoke motor responses of the face, hands, and legs, evidence, perhaps, of areas in the human brain corresponding to the CMAs seen in nonhuman primate anterior cingulate cortex. Recordings in caudal regions have revealed neurons with activity that is modulated during attention-demanding tasks such as arithmetic and generating lists of words. Other neurons, in further caudal and inferior regions, show sensitivity to painful stimuli. Overall, the findings are consistent with those reported in...

The cerebral white matter constitutes approximately onehalf

White matter establishes anatomic connectivity between cortical and subcortical gray matter regions within and between the hemispheres, and it enables more efficient neuronal transmission and cerebral function. Disorders of the cerebral white matter comprise a diverse group of neuropathologic conditions, of which multiple sclerosis is the best known. Neurologic dysfunction is well-known to be associated with these disorders, and neurobehavioral syndromes including dementia are also being increasingly recognized. Recognition of these clinical phenomena represents an opportunity to improve the care of individuals with these disorders and to expand our understanding of the human brain.

Techniques Used in Humans 1 Microstructure

Shorter connections or only incomplete portions of longer connections. Fourth, one class of tracers, lipophilic carbocyanine dyes (Dil and DiO), has been found to bind to the plasmalemma, even in postmortem tissue, and transport by diffusion. These tracers produce high-resolution, Golgi-like labeling, but only within a distance of 2-5 mm of the injection spot. Thus, although evidence supports the applicability of animal data to the human brain, there is a serious need for new techniques that might allow direct investigation of fine axon connectivity in human tissue. Finally, there is an increasing number of antibodies available for immu-nohistological investigation of neural structures. Many of these (e.g., antibodies against peptides, calcium binding proteins, transmitters, receptors, or cytoskeletal elements such as neurofilaments) can successfully be used in human biopsy or postmortem tissue. Most of these markers, however, are for cellular or subcellular components and not...

Clinical Trials in Parkinsons Disease The Prototype for Cell Transplantation

Parkinson's disease is characterized primarily by the degeneration of dopaminergic neurons projecting from the substantia nigra to the corpus striatum. Parkinsonian clinical symptoms like rigidity, tremor, and postural imbalance, accompanied by the histopa-thologic findings of nigral distrophy and Lewy bodies, are well-described and correlate with the loss of dopamine production and release in the brain. The importance of cerebral dopamine became apparent in the late 1950s, and since then our knowledge about the neuroanatomy, physiology, and especially pharmacology of this neurotranmsitter has increased immensely. Readers interested in the topic may start by consulting the chapter in the popular neuropharmacology textbook by Cooper, Bloom, and Roth. Logically, the first therapeutic approach in diseases associated with parkinsonian symptoms, for a long time equated primarily with rigidity, was based on replacing the natural neurotransmitter with precursors like levodo-pa. This has...

Auditory Cortex Is Made up of Multiple Fields to Carry out Parallel and Serial Processing

In all mammals studied, auditory cortex is made up of multiple fields, which are distinguished from one another on both anatomical and functional grounds. The number of such fields varies among species studied from as few as 2 in rodents to as many as 15 in the rhesus monkey. The number, location, and organization of such fields in the human are not fully known. It would be highly desirable, however, to know the functional and structural counterparts of human and monkey auditory cortex. Although much less is known about the functional organization of temporal auditory cortex in the human than in the monkey, from available data there are some striking anatomical similarities between the two species. These data, together with modern imaging functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) and direct electrocorticography (ECoG) and indirect electroencephalography (EEG) and magnetoencephalography (MEG) electrophysio-logical recording data in humans,...

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