Human Brain Ebooks Catalog

Flash Brain Anatomy

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Human brains became larger

A clue to the answer is provided by brain chemistry. The human brain is a fat-rich organ. About 60 percent of its structural material is made up of lipids, most of them long-chain polyunsaturated omega-3 and omega-6 fatty acids. Humans must consume omega fatty acids in their diet because the body cannot synthesize these molecules fast enough from the other fatty acids found in vegetables, nuts, and seeds to supply their brains. Animal brains and livers contain omega fatty acids, but fish and shellfish are by far the best sources. Therefore, because savannas and open woodlands provide few sources of omega fatty acids, the traditional view that early human evolution took place in those environments is being questioned. In contrast, the shores of Africa's many lakes would have been rich sources of fish and mollusks. Thus, access to fat-rich foods from aquatic environments may have been the key factor that supported the dramatic expansion of the human brain. The archeological record of...

Preface to the Second Edition

The aim of this second edition of Magnetic Resonance in Epilepsy is to update readers about this rapidly changing field and its application to human epilepsy. We have retained in part the organization of the first edition with the first three chapters devoted to an introduction to principles that we feel are needed to more fully understand the context of neuroimaging findings. The first chapter is an introduction to epilepsy, written largely for those not familiar with the field. Chapter 2 similarly deals with the principles of MR in a way that is intended to provide an overview of major issues that allow the non-physicist an understanding of how MR works. We hope this will help in understanding the specific findings of later chapters. We felt that Chapter 3 by Henry Duvernoy was a masterpiece in the first edition. There it dealt primarily with the anatomy of the hippocampus and temporal lobe. As the focus of MR has increasing expanded to deal with issues of abnormalities beyond the...

History of Interventions in the Brain Using Psychotropic Substances

Fantasies of intervening in the psyche and the use of psychotropic agents have a venerable history in mankind. Even in prehistoric times, substances like opium, cannabis, coca, peyote and alcohol were used, especially in the context of religious and magic rituals and other cultural practices. In ancient Greece, for example in the Hippocratic writings and the writings of Dioscourides and Galen, the use of opium was recommended for the treatment of pain and sleep disorders, particularly in women. Helleborus was the treatment of choice in psychiatric diseases. The Greek authors distinguished the black helleborus, a purgative, from the white helleborus, a substance which induced vomiting. Ancient Greek medical writings show that doctors believed psychiatric illnesses to have somatic foundations. They therefore tried to heal through the extraction of illness-inducing substances using emetics or purgatives. As can be seen, the concept of the so-called biological psychiatry, meaning physical...

The Future Psychoanalysis Research And Neuroscience

For many years, I am ashamed to admit, any word prefixed by neuro was enough to turn me into an ''anti-brain'' demonstrator. Biology and neuropsychology, I then believed, were irrelevant to an understanding of the human mind. I viewed them as reductionistic attempts that neglected the meaning and affective experiences that I was grappling with in my clinical work and within myself. I situated myself comfortably in the hermeneutic tradition, believing that psychoanalysis was, at the core, about finding meaning and that this had nothing to do with scientific testing or brain anatomy. Indeed, psychoanalysis is, amongst other things, about interpreting meaning. But it has never contented itself with this. Psychoanalytic theories are not simply evocative narratives they expound universal claims about mental events. If psychoanalysis makes universal claims, it has to buttress them with evidence in order to be taken seriously. If, on the other hand, we shy away from this challenge and argue...

Detecting The Protein

In addition to the hypothalamic neurons, the antisera detected a prominent network of axons located within the posterior hypothalamus and beyond. Fiber projections were observed in apparent terminal fields within septal nuclei in the basal forebrain, the preoptic area, the paraventricular nucleus of the thalamus, the central gray, and the locus coeruleus. Less prominent fiber projections were observed in apparent terminal fields within the colliculi, the laterodorsal tegmental nucleus, and the nucleus of the solitary tract. A thorough mapping of these extensive projections from a relatively small number of hypocretin-expressing neurons was published late in 1998.5 The neuroanatomy of the hypocretins in detail is discussed in other chapters.

Reconstruction of Magnetization Distribution Inside a Body from Magnetic Field Measurements

In this last section we turn our attention to a question which, despite being somewhat aside from the main route, is extremely important for applications of magnetism in many areas, and especially in medicine. The question relates to the possibility of reconstructing the complete magnetization configuration inside a body, based on measurements of the magnetic field outside it. If this were possible, then we would obtain a powerful tool for studying areas such as current distribution inside a human brain, This in turn would lead to immense progress not only in the diagnosis of a variety of diseases but also to an understanding of how the human brain functions.

Restorative Neurosurgery by Cells and Genes

However, the neuronal loss in such neurodegenerative diseases may also be ameliorated or even stopped by the implantation of cells that provide trophic support in order to keep the neurons at risk alive. These cell implants should do so by the release of neuro protective or neuralgrowth-stimulatory proteineous compounds. Such factors can not be applied systemically due to a short half life in vivo and the need to apply them locally to prevent any negative side effects on nearby intact systems. The genetic modification of the affected cells, or their neighbouring cells to let them locally produce such factors has also been proposed as a possibility. This does not involve a cell implantation but treatment involving a gene transfer by injection. Cell implantation and genetic modification may even be combined when the implanted cells are modified to express a therapeutic gene. Cell and gene therapy for the diseased or traumatised brain, however, are both invasive interventions in the...

Neurons Act in Networks

The neurons, make up the electro-encephalogram (EEG) which can be measured by placing electrodes on the surface of the skull. The human brain contains about 1011 neurons (about 20 times the world population of humans). Each neuron receives the input of an average of 1,000 synapses on their neurites (having an estimated total length of 100,000 km in the human brain). This is an amazing number of nodes per cell and within the CNS for internal brain communication. Neurons by themselves are functionless units. However grouped, either in nuclei or in layer structures, neurons make up networks that mutually interact to form information-processing units. Within a substructure of the brain, different types of neurons have different connections and use different chemical compounds for signal transfer. These neurotransmitters reach different types and quantities of receptors on the target site of the synapse, thereby affecting intracellular molecular machinery in the receiving cells. For a...

The Start Of A Collaboration

After obtaining the New Jersey tissue, we had enough virus-containing tissue to begin serious work. We began what turned into a long and frustrating series of efforts to cultivate the virus from the diseased tissue. We tried explants of the fresh brain tissue, but after many weeks of coaxing and coddling only a few fibroblasts and astrocytes grew. We made 10 extracts of diseased brain tissue and clarified it by centrifugation and then used the supernatant fluid to inoculate cell cultures. A similar extract of normal human brain tissue was used on control cultures. Monolayer cultures of primary and secondary human embryonic kidney cells, Hep-2 cells, and human fibroblasts were inoculated. None of these cell cultures showed any evidence of being infected even after weeks of cultivation and medium changes and subculturing. Mice, newborn mice, and hamsters were inoculated by the intracerebral and peritoneal routes and were observed for many months without showing signs of disease or...

Historical Outline of Neurotransplantation in Human Beings

The history of neural grafting in human PD can be seen as the test bed for neuron supplementation techniques as a therapeutic intervention in the human brain. It showed cell implantation deep inside the brain to be surgically feasible and proved that restorative neurosurgery using immature neurons is possible, at least in principle.

The Issue of Secondary Epileptogenesis

How these observations in animal models relate to the origins of human epilepsy and to the secondary effects of seizures seen in the human brain remains controversial. Morrell used the criteria of unequivocal evidence of independent interictal or ictal epileptiform discharges in the hemisphere contralateral to a well defined tumor to demonstrate the phenomenon of the mirror focus in humans. He showed an incidence of up to 36 of what he called 'secondary epileptogenesis,' with 15 of patients having clinical attacks arising from this focus. While the demonstration of secondary epileptogenesis in humans is indirect, many epileptologists would accept the possibility of secondary epileptogenesis in their patients. It is possible that this phenomenon is the basis of the well-described 'dual pathology' of hippocampal sclerosis in patients with a tumor or other lesion elsewhere. The alternative view is that damage occurs bilaterally at the time of the original epileptogenic insult and that...

Seizureinduced Brain Damage

Therefore we can only conclude with some speculations (and opinions) - that sometimes seizures damage the brain but do not always do so. Furthermore, hippocampal sclerosis may occur as a primary lesion that is the consequence of unknown insults, but hippocampal sclerosis can also arise as a secondary lesion (like kindling) as a consequence of seizures originating elsewhere. In this latter instance, even if the initial seizures arise elsewhere, the hippocampus may become the primary seizure focus later in life. It is our opinion that the noninvasive techniques of MR investigation of the human brain that are described in this book provide the means whereby these issues can be more fully addressed.

The Practice of Clinical Neurotransplantation

In practice, neurotransplantation in defective areas of the human brain consists in the precisely directed injection of microliter quantities of suspensions of nerve cells or tissue fragments prepared from defined areas of fetal brain known to contain the needed cell type in an immature state or prepared from cells specially cultured and modified for it in the laboratory. The injected mass is about 100,000 times smaller than the volume of the adult brain (approximately 1.5 liter). This type of intervention requires surgical precision and accuracy, but it is not an extremely severe, physically invasive operation on the patient. Transplanted nerve cells have to mature and integrate for proper restoration of the lost brain function to occur. The possible therapeutic effects of neurotransplantation are, therefore, never immediate, but develop over a period of several months, not unlike the time frame of brain cell maturation in the intrauterine fetal stages (Isacson and Deacon 1997).

Compositional Changes in the Developing Brain

The DNA content of brain is considered to be a reliable indicator of cell number. The period of cellular proliferation can,therefore,be followed by measuring the amount of DNA per brain volume. In human brain two major periods of cell proliferation have been detected by measuring DNA levels. The first period begins at 15-20 weeks of gestation and corresponds to neuroblast proliferation. The second period begins at 25 weeks of gestation and continues into the 2nd year of postnatal life. This latter period corresponds to multiplication of glial cells and includes a second wave of neuronogenesis, producing mainly cerebellar neurons. Table 1.3. Lipid composition of human brain during development. From Svennerholm (1963) Table 1.3. Lipid composition of human brain during development. From Svennerholm (1963)

Are the Cognitive Changes During Acute Hypoglycaemia Important and Valid

Just as more studies that examine the practical cognitive aspects of hypoglycaemia would be useful, so would more studies of the brain's processing efficiency. Cognitive tests typically involve a melange of inseparable mental processes, and yet very specific aspects of the human brain's activities can be measured in the clinical laboratory (Massaro, 1993). Studies of the cognitive effects of hypoglycaemia have thus begun to address the impairments to various cognitive domains in more detail. Basic, specific aspects of visual and auditory processing have been examined during acute hypoglycaemia in non-diabetic humans. Standard tests of visual acuity - those that are measured by an optometrist - are not affected by hypoglycaemia, but other aspects of vision are affected (McCrimmon et al., 1996). These include

Survey of Current Experimental Human Applications of Restorative Neurosurgery

Clinical application of cell implantation and gene transfer in human brain disorders has not reached the level of therapy. All treatments still are in the experimental phase as the beneficial functional outcomes are variable, unpredictable or not present at all. The following section surveys briefly the achievements in this area to date.

Behavioral Evidence for Magnetic Sensing

Many animal ethologists studying migration have found strong direct evidence that the Earth's magnetic field is used in conjunction with other sensory modalities for guidance. Unfortunately, the location of the neural receptors responsible for static magnetic field sensing are known in few cases (see Section 2.4.2). Some magne-toreceptors are thought to use cells containing microscopic magnetic iron oxide (magnetite) crystals that interact with the Earth's magnetic field to create forces that are somehow transduced to nerve spikes. Other workers have implicated elements of the visual system in magnetoreception. The bottom line is that at this time there is no hard evidence for a specific mechanism for magnetoreception, even in Tritonia Pd5 neurons. Much basic neurophysiology and neuroanatomy has yet to be done.

When is a Brain Disorder Eligible for Cellular or Molecular Surgery

The history of cellular intervention in the human brain started with the autologous implantation of adrenal medulla tissue fragments in the stria-tum of the PD patient. The first presentation of these studies immediately provoked the question whether enough basic studies had been performed to justify such an experimental clinical treatment. Adrenal implantation in rat models for the parkinsonian dopaminergic failure of the brain have shown reversal of the motor symptoms, but is it enough evidence to justify a clinical trial One of the fundamental requirements in clinical research is that a sufficient body of animal studies, in particular those carried out in non-human primates, be reported before trials on human beings can be performed. It will, however, always be difficult to determine what volume of animal results justifies the intracranial application of cells or genes in A basic requirement, however, is obviously that any brain disorder elected for cell or gene transfer must have...

How to Design a Meaningful Experimental Human Cell or Gene Therapeutic Neurosurgical Study

Facing a future with various types of therapeutic cell and gene trials in various human brain diseases, strategies on how to control efficacy of these new treatments needs to be discussed. Human experiments that are methodologically bound to give non-interpretable results are unethical (Felten 1994). However, this is also true of unnecessary control treatments in human beings. Randomised blind evaluation clinical trial methodology has been the gold standard for establishing the effectiveness of medicines for the last 50 years. The standard trial must show that a particular drug treatment correlates with a hypothesised outcome and that no other factors are responsible for this correlation (Kenny 1979). In the case of individual human subject, one cannot simultaneously both give and withhold a treatment. The comparison of patients pre- and post-treatment is hard to measure accurately and can easily be biased by artifacts (Kraemer 2004). It is, therefore, regarded as inferior to a...

Ethically Acceptable Retrieval and Use of Donor Material

Nowadays, experimental cell restorative surgery in the human brain primarily uses human fetal tissues. Clearly it would have been desirable to circumvent the ethical problems related to the use of the remains of elected human abortions, which provide the only feasible source of neuronal grafts. Ethical guidance for the retrieval and use of the remains of human abortions has been developed to solve the issue, though for parts of society, in several countries, the use of human abortion tissue (as well as abortion itself) remains, and will continue to remain, controversial or even forbidden. Cell therapies based on cells obtained from adult donors, via self-donation, or on long term established laboratory cell lines (implants from the shelf) would be an ideal alternative. Discoveries about the potencies of stem cells - cells that can clone themselves indefinitely and can start to grow and differentiate into any type of cell in the body by external clues - may perhaps make the latter...

Applications of Image Analysis in the Study of the CNS Morphology

One of the primary reasons for using digital image analysis in neuroanatomy is to statistically summarize and evaluate a structure to allow comparisons among populations. Digital image analysis offers a wide range of possibilities that are very useful when analyzing morphological changes. In this particular study, densitometry and morphometry, which are widely utilized functions of the digital image analysis, were used. Densitometry was employed to estimate the relative concentrations of different antigens detected by immunocytochem-istry, while morphometry was used to study cell morphology and the relative area covered by cellular projections. Digital image analysis allows one to semi-quantify immunocytochemical experiments because it is capable of measuring simultaneously the labeling intensity, localization, size and shape of the labeled profiles.

Electromagnetic Tissue Properties

Most important is the tissue conductivity, which differs depending on the tissue type. The spread of extracellular currents caused by cellular electric activity is mainly confined to the inside of the skull. The brain tissue inside the skull may be compared to a compartment with similar conductivity within (gray matter ca. 0.3 S m-1, white matter 0.14 S m-1) surrounded by a compartment with high conductivity such as liquor (ca. 1.54 S m-1). The symmetry of extracellular currents is distorted by these conductivity barriers. Tissue permeability can be considered constant in living tissue. Studies of the heads of piglets, which have a gyrencephalic brain similar to the human brain, show that the bone is of almost no importance in the distribution of the magnetic field. A detailed analysis provides evidence that only small changes in the magnetic field occur if the current dipole is located deep within the brain, causing weakening of the amplitude if the bone is removed (Okada et al.,...

Finally Some Glimmering Of Success

Billie had been working hard for months trying to improve cultures of PHFG cells. It was slow going. Initially the cultures consisted of astrocytes that would form a monolayer, but spongioblasts were either sparse or absent. We thought it important to have good cultures of spongioblasts because neurobiologists considered spongioblasts to be precursors of oligodendrocytes, the cells in which the virus was found in human brain.

Theoretical Models For Neural Signal Conditioning

This section examines several simple, theoretical neural models for conditioning and selecting features from a train of spikes from a receptor or interneuron. Such mechanisms may, in fact, exist in nature. Whether they can be identified in natural neurophysiological systems depends on future research in neural signal processing and neuroanatomy. They are considered biomedical engineers because they offer useful signal processing paradigms with simple structures. Their actual existence in nature would not be surprising.

Supervenience and Epiphenomenalism

The Martian and I are in different first-order states. We are in the same second-order causal functional state, but that does not suffice to put us in the same phenomenal state, if that is a local, inner, first-order state. Something more is required. Using the theological metaphor, we require a decision by God to grace the Martian's Mars-brain states and my human brain states with the same subjective character. God has to decide that functionally equivalent states should cause the same subjective character. But that would amount to (D), causal supervenience. And of course if God could have made the decision to grace both the Martian and me with the same subjective characters, he could also have made the decision to take the day off and grace nobody with any qualia the Chalmers zombie world. Subjective characters cannot be identified with functional states, the argument goes, and so must causally supervene upon them.

Basic Distinctions and Affiliated Questions

Perhaps the first and most obvious question to be asked in aiming at conceptual clarity is this What do we mean by applying the concept of enhancement to human mental capacities and what are the respective techniques, when applied in practice, supposed to achieve The mind-enhancing methods, which concern us here, are those new and powerful techniques described above. These must be distinguished from traditional methods of mental enhancement such as studying, meditating, drinking coffee, taking vitamins, promoting social interaction in young children (cf. Kutnick and Kington 2005), or modifying other environmental circumstances in certain favourable ways. The enhancement problems we engage with arise primarily out of the use of biotechnologies that aim at directly manipulating the human brain and whose practical realisation is, in a broad sense, a matter of the technical competence of medical professionals. This broad sense is meant to encompass any legitimate professional medical...

Assessment of the Neurochemical Profile Using MRS

1H-MRS studies have also been carried out in Tg2576 83 and in PS2APP mice 74 . In vivo 1H spectra of the frontal cortex of 19-month-old Tg2576 mice revealed significant decreases of NAA and increased levels of taurine compared to wildtype control mice. Subsequent in vitro MRS in corresponding areas of the cortex showed in addition decreased levels of glutamate and glutathione 83 . The decreased levels of NAA and the increased level of taurine are consistent with neuronal variability and increased glial volume, being equivalent to findings of decreased NAA and increased myo-inositol in human AD 82,84 . Taurine is much more concentrated in the rodent than in the human brain and may serve a similar role as myo-inositol in the human brain. Decreased NAA creatine and glutamate creatine ratios have been found in the frontal cortex of 24-month-old double-transgenic PS2APP mice compared to age-matched controls 74 . In a longitudinal study in the same model from age 4 to 24 months, the...

Concerns about the Corruption of the True Nature of Human Beings

Between ethically permissible interventions into natural human conditions, and other interventions that we should avoid or prevent.256 Such reasons might be concerned with two different types of risks. On the one hand, certain risks will be associated with the possible emergence of features that humans do not naturally possess and that, for various reasons, we would not want them to be endowed with. On the other hand, risks may also be associated with the danger that the very complex interplay of biological features, especially in the human brain, might be profoundly distorted by the unnatural enhancement of one set of features at the expense of others. Turning to the first set of risks, one might think of physical capacities such as a bat-like radar vision or a plant-like ability to photosynthesise (each affiliated with a host of incalculable consequences), or mental capacities, such as the ability to block out from one's consciousness any vestige of empathy towards fellow humans.257...

Neurogenesis In The Adult

As if the processes for establishing and maintaining long-term memory weren't already complicated enough, recent findings indicate that hitherto unanticipated mechanisms also may play a role. Specifically, neurogenesis has entered the picture. When I was a young scientific sprout, the dogma was that there is no new generation of neurons in the adult CNS. However, fascinating recent results have shown that neurogenesis does indeed continue into the adult, particularly in the dentate gyrus. One key publication by Fred Gage and his colloborators showed specifically that new neurons are generated in the adult human brain (73). How might one be able to ascertain this fact Cancer patients sometimes receive treatment with the drug Bromo-deoxy Uridine (BrdU). It selectively affects dividing cells by being incorporated into their DNA upon de novo DNA synthesis. Therefore, an ancillary aspect of this is that BrdU selectively labels freshly divided cells. Post-mortem analysis of the brains of...

Imaging The Celldeath Stage Of Alzheimers Disease With Volumetric

Almost as soon as imaging techniques began visualizing brain anatomy in living subjects, investigators applied the technique to search for anatomical correlates of brain disorders, including AD. By the late 1980s, a number of groups sprearheaded the effort to translate the exquisite anatomical detail provided by MRI into a clinically meaningful tool 42-45 . Since that time, additional groups have introduced protocols that are ideally suited to quantify the volume of the entorhinal cortex and the rest of the hippocampus 46-53 . Multiple studies have now applied these approaches, both cross-sectionally as well longitudinally, typically documenting entorhinal volume loss as the best indicator of disease.

Functional DWI in Brain Mapping

Using fast-DWI, Le Bihan and colleagues observed changes in the apparent diffusion coefficient of water in the human brain visual cortex during activation by a flickering checkerboard task activation paradigm (Darquie et al., 2001). The ADC decrease was less than 1 but significant and reproducible, and closely followed the time course of the activation paradigm. The observed ADC findings were as

Magnetic Susceptibility and B0 Inhomogeneity

Fig. 3.58. (A) Numerically computed saggital susceptibility field map in human brain. (Truong et al., 2002). (B) Gradient echo image of the same subject using TR TE 600 ms 12 ms, nominal flip 22.5 , FOV 18 cm, 1024 x 512, 2 mm slice thickness. (C) Matching flip angle map and (D) receive sensitivity map, Fig. 3.58. (A) Numerically computed saggital susceptibility field map in human brain. (Truong et al., 2002). (B) Gradient echo image of the same subject using TR TE 600 ms 12 ms, nominal flip 22.5 , FOV 18 cm, 1024 x 512, 2 mm slice thickness. (C) Matching flip angle map and (D) receive sensitivity map,

Brain Evolution and Tool

Why did the human brain increase in size so much A full explanation is presently hampered by the fact that we know so little about the brain's workings, particularly of the difference in brain function between man and chimpanzee or gorilla. Recent landmark advances in nuclear magnetic resonance (NMR) imaging and positron emission tomography (PET), which provide high spatial and temporal resolution for noninvasive investigations of the living brain, will reveal much in the future, particularly for the study of higher mental functions. Experiments and investigations of brain-damaged patients have already identified an impressive number of control and information-processing centers, and allow some partial answers to be given. Figure 7.34 shows in cross-section areas of the human brain, overlaid with pictorial representations of the body parts that they control. As the brain devotes larger areas to those parts that receive more attention, these have been magnified out of proportion to...

Conclusion and Outlook

Damier, P., Hirsch, E.C., Agid, Y., and Graybiel, A.M. (1999). The substantia nigra of the human brain I. Nigrosomes and the nigral matrix, a compartmental organization based on calbindin D(28K) immunohisto-chemistry. Brain, 122, 1421-1436. Gelman, N., Gorell, J.M., Barker, P.B Savage, R.M., Spicklee, E.M., Windham. J.P., and Knight, R.A. (1999). MR imaging of human brain at 3.0 T preliminary report on transverse relaxation rates and relation to estimated iron content. Radiology, 210. 759-767. Georgiades, C.S., Itoh, R., Goiay, X., van Zijl, P.C.M., and Melhem, E.R. (2001). MR imaging of the human brain at 1.5 T Regional variations in transverse relaxation rates in the cerebral cortex. Am. J. Neuro-radiol, 22, 1732-1737. Glover, G.H. (1999). 3D z-shim method for reduction of susceptibility effects in BOLD fMRI. Magn. Reson. Med., 290-299. Hallgren, B. and Sourander, P. (1958). The effect of age on the non-haemin iron in the human brain. J. Neurochem., 3, 41-51. Laurent, W.M., Bonny,...

Dealing with Side Effects of Enhancements

We do not endorse a principled ethical rejection, let alone an outright legal prohibition, of interventions in the human brain aimed at mental enhancements solely on grounds of their physical or mental risks for the affected individual. It must be underlined, however, that potential negative side effects of mere enhancements weigh more heavily against intended positive effects than they would in treatment cases. Physicians intervening for enhancement purposes alone have enlarged informational duties towards their clients. To the extent that their duties to patients are increased, they are also obliged to acquire pertinent additional information for themselves.

Modelling the Effect of Chemotherapy on Tumour Growth

Part on quantitative image analysis of histological sections of a human brain glioma and especially on cross-sectional area volume measurements of serial CT images while the patient was undergoing chemotherapy. We estimated the model parameters using optimization techniques to give the best fit of the simulated tumour area to the CT scan data. We carried out numerical simulations on a two-dimensional domain, which took into account the geometry of the brain (only the ventricles and the skull) and its natural barriers to diffusion. The results were used to determine the effect of chemotherapy on the spatiotemporal growth of the tumour. (Shochat et al. (1999) have used computer-based simulations of various basic ordinary differential equation models to evaluate the efficacy of chemotherapy protocols on breast cancer.)

Neurons function in networks

As we learn more about the properties of neurons, it is important to keep in mind that nervous systems depend on neurons working together. The simplest neuronal network consists of three cells a sensory neuron connected to a motor neuron connected to a muscle cell. Most of the neuronal networks that carry out the functions of the human nervous system are much more complex and consist of many more neurons. The human brain contains an estimated 1011 neurons, and most of those neurons receive information from a thousand or more synapses thus, there may be as many as 1014 synapses in the human brain. Therein lies the incredible ability of the human brain to process information.

Neural Models of Pattern Formation

Perhaps the most obvious complex spatial patterning processes are those associated with the nervous system such as pattern recognition and the transmission of visual information to the brain. This is a vast field of study. In this chapter we give only an introduction to some of the models, involving nerve cells, which have been proposed as pattern generators. Basic to the concept of neural activity is the nerve cell, or neuron. The neuron consists of a cell body with its dendrites, axon and synapses. It is a bit like a tree with the roots the dendrites, the base the cell body, the trunk the axon and the numerous branches the synapses. The cell receives information, from other cells, through its den-drites, passes messages along the axon to the synapses which in turn pass signals on to the dendrites of other cells. This neuronal process is central to brain functioning. The axons are the connectors and make up the white matter in the brain with the dendrites and synapses making up the...

The Mammalian Nervous System Structure and Higher Functions

HA Far Side cartoon by Gary Larson shows a classroom with pupils at their desks. One pupil with a noticeably small head and his hand raised says, Teacher, may I be excused My head is full. This amusing cartoon suggests a deep question What is the capacity of the human brain Is it limited by size, number of neurons, number of synapses The unit of function of the brain is the neuron. The human brain consists of about 100 billion neurons, which account for its ability to handle vast amounts of information. In the previous two chapters we learned about the cellular properties of neurons. In this chapter we take on the challenge of understanding some functions of the human nervous system in terms of these cellular mechanisms.

Editorial Comments

Functional magnetic resonance imaging (fMRI) has the capacity to provide data with spatial and temporal resolutions exceeding those achieved by other currently available methods of noninvasive investigation of brain function. This fact coupled with the ability of the technique to perform serial studies makes fMRI an attractive tool for investigating the effects of pharmacological agents in the animal and human brain, as extensively discussed in Chapter 10 and Chapter 11. However, there are various associated complications to be taken into account, such as the different means by which drugs may interfere with the mechanisms that give rise to the pharmacologically induced fMRI signal, and local or global cardiovascular changes that might produce functional responses unrelated to neural activity. Furthermore, in animals, there is the complicating effect of anesthesia. Proper consideration of these concerns, along with careful attention to experimental details and verification procedures,...

Cytokines In The Normal Central Nervous System

TNF-a is another cytokine that has been detected in normal CNS however, similar to IL-1P, its expression is controversial (1,16). TNF-a and its receptors have been detected in discrete brain regions of normal mouse, rat, and human brain, including the hypothalamus, cortex, and cerebellum (17-20). In contrast, a few groups have been unable to demonstrate any TNF-a in the normal CNS

Hypoglycaemia and Mental Functions in Children and Adolescents

There is controversy about whether repeated episodes of severe hypoglycaemia have lasting effects on the thinking skills of children (Ryan et al., 2005). In addition to the severity of hypoglycaemia, the age of the individual is important in determining the potential impact of hypoglycaemia on the brain (Ack et al., 1961). The human brain develops rapidly until the age of five years, and during this critical period any insult can have long-lasting effects. In diabetic children important risk factors for the development of later cognitive impairment are as follows (Ryan, 1988 1997)

What is the Hypothetical Nature of the Extraterrestrials

We have mentioned above that these extraterrestrials, in an evolutionary stage comparable to us today, may have had a body fairly similar to ours, based on organic chemistry. Yet in Chap. 9 it was speculated that in the future, after the construction plan of the human brain becomes known, there might be self-conscious human-like beings, androids, which have bodies that are no longer built on the basis of organic chemistry. Both in size and shape, androids could be very different from what we see in today's biological world. It is therefore obvious that when picturing extraterrestrial beings, millions of years older than us, we must expect them to look very dissimilar to us.

Mirror Neurons Gestures and the Origins of Metaphor

It is important to emphasize that what is activated in mirror neurons is not simply a response to the visual perception of the object, for these neurons fire only when a specific action is observed. Seeing the object itself will not cause the neurons to fire. Of particular interest is that the specific area of the monkey's prefrontal cortex area that contains mirror neurons (F5) is thought to be homologous with Broca's area in the human brain, so the relational specificity of motor actions may constitute an analog for what in the human brain evolved into a capacity to imitate the precise sounds of speech. As Rizzolatti and Arbib state, This observer execution matching system provides a bridge from doing to communicating (1998). tion was the engine that produced the modern human brain (1991). He suggested that ancient hominids, who showed left-brain asymmetry, lacked the vocal apparatus for modern speech. They presumably had the capacity for a more complex method of communication than...

Metabolic Functional Imaging Methods Pet And Fmri

Functional brain imaging methods have revolutionized our understanding of how the human brain works, exploding onto the fields of neuroscience and medicine, giving us unprecedented opportunities to see the human brain in action 1-3 . There is a growing range of methodologies available, each with pros and cons (see also Chapter 10, Section 10.1). Figure 11.1a displays the physiological correlates of brain electrical activity, and the corresponding available methods to measure them. Other methods not shown here but equally important for assessing function within the human brain include magnetic resonance spectroscopy (MRS) 4,5 , diffusion weighted imaging, and tractography 6-8 (see also Chapter 10, Section 10.2.5). Their potential application to clinical pharmacological studies is similarly being realized at present but a discussion of this is outside the remit of this chapter.

The Brain is Seat of the Human Mind

5 This uniqueness is further explained by the (albeit fictional) thought experiment of human brain transplantation. The result will be that the brain donor will see him- herself as having received a new body. On the other hand, the recipient 'person' will cease to exist. Brain transplantation, therefore, does not exist or should be defined as body transplantation.

Neuronal Degeneration

A degenerin-like channel, initially known as MDEG or BNaC1, has also been cloned from human brain (Waldmann et al., 1996 Garcia-Anoveros et al., 1997). This channel has been renamed ASIC2, as it is now known to belong to the H+-gated cation channel family. It did not express in Xenopus oocytes or mammalian cell lines unless a point mutation was introduced at glycine 430, the position corresponding to the site of mutations which cause neurodegeneration in C. elegans. Cells expressing the mutant form of ASIC2 exhibited an amiloride-sensitive Na+ current and died rapidly. The role of ASIC2 in human brain is unknown but it is clear that it would cause neuronal degeneration if it were to become permanently activated. Possibly, therefore, it may be implicated in human neurodegenerative disease.

Direct and Indirect Gene Transfer in the Brain

Indirect Gene Transfer

Currently lentiviral (LV) vectors and adeno-associated viral (AAV) vectors are vectors that efficaciously and directly transduce the CNS tissue without direct or short term toxicity for neuronal cells. Whether it is safe for use in the human brain in the long term still has to be established. Clinical trials with both ex vivo gene transfer and direct gene transfer are currently being performed in PD and AD patients (see below).

Evolution of DWI Changes in Stroke

Dwi Brain Ischemia

A series of diffusion-weighted images of human brain at 4 h after onset of cerebral ischemia. EPI T2-weighted (in which no diffusion-weighting is applied, b 0), the corresponding diffusion-weighted images (b 881 s mm2), and the calculated ADC maps for four slices of 16 images acquired from a patient at 4 h after onset of hemi Fig. 3.51. A series of diffusion-weighted images of human brain at 4 h after onset of cerebral ischemia. EPI T2-weighted (in which no diffusion-weighting is applied, b 0), the corresponding diffusion-weighted images (b 881 s mm2), and the calculated ADC maps for four slices of 16 images acquired from a patient at 4 h after onset of hemi

Structure Function and Information Flow

Forebrain Structure And Function

46.2 Development of the Human Nervous System Three swellings at the anterior end of the hollow neural tube in the early vertebrate embryo develop into the parts of the adult brain.The final view is an adult human brain cut in half through the midline. 46.2 Development of the Human Nervous System Three swellings at the anterior end of the hollow neural tube in the early vertebrate embryo develop into the parts of the adult brain.The final view is an adult human brain cut in half through the midline.

Structural Organization of the Brain

Interventricular Foramen

Ciate appropriate motor responses with sensory stimuli, and thus to maintain homeostasis in the internal environment and the continued existence of the organism in a changing external environment. Further, the central nervous systems of all vertebrates (and most invertebrates) are capable of at least rudimentary forms of learning and memory. This capability most highly developed in the human brain permits behavior to be modified by experience and is thus of obvious benefit to survival. Perceptions, learning, memory, emotions, and perhaps even the self-awareness that forms the basis of consciousness, are creations of the brain. Whimsical though it seems, the study of brain physiology is the process of the brain studying itself.

Focal High Frequency Electrical Brain Stimulation

Progressive Spastic Ataxia

During the past decades focal high frequency electrical stimulation of the human brain has been used in order to treat the symptoms of several neurological disorders, including Parkinson's disease, essential tremor, dystonia, epilepsy and Tourette's syndrome. In the human brain neuronal circuitries have been detected which are responsible for motor control, others enable reception of information from the different sense organs (vision, hearing, sensation, taste, smell), still others are responsible for emotion, sexual behaviour, intelligence, memory etc. These circuitries do not simply exist in parallel to one another. Rather, there exist important connections in between them. Transmission of information runs via action potentials within one neuron and via neurotransmitters being released at the synapses in between neurons. Action potentials are transient electrical depolarisations of the cell membrane which propagate the signal from one place to another in the cell. Technically, it...

Current Limitations Possible Solutions and Enhancement Technologies

Implants have a general disadvantage over other methods employed to restore or even enhance neural function they involve a more or less invasive surgical procedure. Still, their development has been pursued with considerable perseverance for a number of important reasons, which we have to keep in mind when wondering why anybody would seriously consider surgical connection of artificial devices to the human brain Neural implants

Afferent Connections Of Hcrt Neurons

Circadian modulation of the Hcrt neurons is suggested by the presence of a small number of direct projections from the SCN seen in the rat with anterograde tracing, as well as apposition with arginine-vasopressin (A VP)- and vasoactive intestinal peptide (VIP)-immunoreactive fibers, whose cell bodies are found in the SCN in the human brain.29 Furthermore, Hcrt neurons receive innervation from the DMH, a region that receives dense SCN input that is GABAergic and glutamatergic.98

Central Mechanisms Of Penile Erection And Flaccidity

And genital sensations but does not lead to penile erection. Conversely, stimulation of cortical-subcortical areas linked to the limbic system elicit penile erections in response to stimulation, as demonstrated in monkeys (5,171-173). Direct study of the human brain is limited to observations made during neurosurgical procedures. Conversely, stimulation of the amygdala (a limbic structure) can induce erotic emotions similar to those experienced during intercourse. Analogous observations have been made by comparing the experiences of patients suffering from epilepsy with parietal lobe foci to those with mediobasal temporal foci. Animal experiments have shown that damage to the fornix and prefornical area also injures the paraventricular nucleus (PVN) outflow to the MFB, possibly accounting for the impotence associated with these operations.

Stegeman 1967 On Auditory Learners

Barth, D.S., Sutherling, W., Engel, J. Jr and Beatty, J. (1982). Neuromagnetic localization of epileptiform spike activity in the human brain. Science, 218, 891-894. Brenner, D., Williamson, S.J., and Kaufman, L. (1975). Visually evoked magnetic-fields of human brain. Science, 190 (4213), 480-482. Brenner, D., Lipton, J., Kaufman, L., and Williamson, S.J. (1978). Somatically evoked magnetic fields of human brain. Science, 199 (4324), 81-83. Deecke, L., Weinberg, H., and Brickett, P. (1982). Magnetic fields of the human brain accompanying voluntary movement. Bereitschaftsmagnetfeld. Exp. Brain Res., 48 (1), 144-148. HAmAlainen, M., Hari, R., Ilmoniemi, R.J., Knuutila, J., and Lounasmaa, O.V. (1993). Magnetoencephalography - theory, instrumentation, and applications to non-invasive studies of the working human brain. Rev. Modern Physics, 65, 413-497. Mauguiere, F., Merlet, I., Forss, N., Vanni, S., Jousmaki, V., Adeleine, P., and Hari, R. (1997). Activation of a distributed...

The Cerebral Cortex Is Functionally Compartmentalized

Primary Somatic Sensory Cortex

In the human brain, the surface of the cerebral cortex is highly convoluted, with gyri (singular, gyrus) and sulci (singular, sulcus), which are akin to hills and valleys, respectively. Deep sulci are also called fissures. Two deep fissures form prominent landmarks on the surface of the cortex the central sul-cus divides the frontal lobe from the parietal lobe, and the sylvian fissure divides the parietal lobe from the temporal lobe (Fig. 7.8). The occipital lobe has less prominent sulci separating it from the parietal and temporal lobes.

Memory and Learning Require the Cerebral Cortex and Limbic System

Septal Nucleus Basal Forebrain

Memory and learning are inextricably linked because part of the learning process involves the assimilation of new information and its commitment to memory. The most likely sites of learning in the human brain are the large association areas of the cerebral cortex, in coordination with subcortical structures deep in the temporal lobe, including the hippocampus and amygdala. The association areas draw on sensory information received from the primary visual, auditory, somatic sensory, and olfactory cortices and on emotional feelings transmitted via the limbic system. This information is integrated with previously learned skills and stored memory, which presumably also reside in the association areas.

Glial cells are also important components of nervous systems

Schwann Cell

Neurons are not the only type of cell in the nervous system. In fact, there are more glial cells than neurons in the human brain. Like neurons, glial cells come in several forms and have a diversity of functions. Some glial cells physically support and orient the neurons and help them make the right contacts during embryonic development. Other glial cells insulate axons.

Thyroid Hormones Are Essential for Development of the Central Nervous System

The human brain undergoes its most active phase of growth during the last 6 months of fetal life and the first 6 months of postnatal life. During the second trimester of pregnancy, the multiplication of neuroblasts in the fetal brain reaches a peak and then declines. As pregnancy progresses and the rate of neuroblast division drops, neuroblasts differentiate into neurons and begin the process of synapse formation that extends into postnatal life.

Average body weight kg

A cross-section of the human brain overlaid with the body parts that the respective brain areas control (after Taylor et al. 1997) Fig. 7.34a,b. A cross-section of the human brain overlaid with the body parts that the respective brain areas control (after Taylor et al. 1997)

Conduction and Transmission of Cellular Activity

Glia Level Scalp

Left The human brain is gyrence-phalic, characterized by gyri and sulci. Orientation of neurons changes with respect to the brain surface caused by the folding of the gray matter. The main axis of pyramidal cells is in some cases tangential and in some cases perpendicular to the surface. Fig. 2.42. Left The human brain is gyrence-phalic, characterized by gyri and sulci. Orientation of neurons changes with respect to the brain surface caused by the folding of the gray matter. The main axis of pyramidal cells is in some cases tangential and in some cases perpendicular to the surface.

Myelination of the Nervous System

Myelination of each of the multiple connecting fiber systems of the CNS takes place at a different time in early development. Some fiber systems start to myeli-nate halfway through gestation or later and rapidly attain their maximal degree of myelination, whereas other systems attain their maximal degree of myeli-nation only slowly. It is, therefore, not correct to refer to myelination as a singular process. There is a marked, temporal diversity in topographic patterns of myelination throughout the last half of gestation and during the first 2 postnatal years. Thus, at any time in the early development of the human brain there are multiple separate or intermixed regions of unmyelinated, partly myelinated, or completely myelinated tracts.

Patricia Tagliaferro Alberto J Ramos Emmanuel S Onaivi Sergio G Evrard Maite Duhalde Vega and Alicia Brusco

One of the major goals for the use of digital image analysis systems in neuroanatomy is to visualize structures, cells, or other tissue components in order to compare various populations. In addition, digital image analysis allows semi-quantification of cell labeling because it is capable of measuring simultaneously the staining intensity, location, size, and shape of labeled profiles. In the present work, the morphological changes in the CB1 hippocampal area and corpus striatum induced by chronic treatment with the synthetic CB1-receptor agonist WIN55,212-2 were analyzed as an example of digital image analysis application. Twice-daily treatment for 14 d with the CB1-receptor agonist demonstrated significant changes in the expression of neuronal cytoskele-tal proteins and in neuronal morphology, as evidenced by immunocytochemical and digital analysis studies. However, changes in the expression of astroglial cytoskeletal proteins were not found.

Decision Support Systems

Formalization and structuring of medical data and knowledge is not easy. Even in the case where we admit that all scientific and empirical knowledge is stored in computer we only can propose expert systems based on our currentmethodological achievements on how to make decision proposals. Till recently we have not known how the human brain process collects data and knowledge. In contrast to the human brain, decision-making using an expert system has been well described. Thus, the dream of the computer that performs at a high level of competence over a wide variety of tasks that people perform well seems to rest upon knowledge in the task areas.

The Suprachiasmatic Nucleus

The suprachiasmatic nucleus (SCh) is the major biological clock of the brain and provides an entrance for visual afferent signals to the circadian circuitry of the brain.136, 137 see ref 138 A direct projection from the SCh to both the Hcrt and MCH cells has been described in both rat and human brain 67 see also ref 139. These projections derive from the shell (predominantly containing the neuropeptide, arginine-vasopressin) as well as the core (predominantly containing the neuropeptide, vasoactive intestinal peptide) of the SCh.67 Notably, the diurnal changes in Hcrt expression and peptide content140, 141 disappear following destruction of the SCh.142 The major recipient of SCh innervation in the brain is the subparaventricular zone,139,143 which plays a role opposite to the LHA in arousal, since lesions targeting this region (in its ventral aspects) result in decreased

T1 and T2weighted MRI in patients with carotid territory TIA or stroke

What Left Insular Cortex

When cerebral blood flow falls to between 10 and 15 ml 100 g minute, ischaemia-induced failure of the neuronal membrane sodium pump results in the intracellular accumulation of sodium and water with resultant neuronal swelling (cytotoxic oedema) 39 . Because T1-weighted MRI is useful for looking at normal brain anatomy, one may identify morphological swelling of the grey matter and subtle effacement of sulci on T1-weighted images in the acute phase after ischaemic stroke (within the first 2-4 hours), which is presumably secondary to cytotoxic oedema 94 . Although this can occur before high signal is seen on T2-weighted images, these changes may be very subtle and may not be reliably identified, and one cannot exclude acute cerebral infarction if T1-weighted MRI of brain is normal.

History of Twoway Communication between Electrodes and the Brain

In 1870, two German researchers (Eduard Hitzig and Gustav Fritsch) electrically stimulated the brains of dogs. They found that areas in the cerebral cortex were related to motor function. Another German, Fedor Krause, one of the fathers of modern neurosurgery, systematically mapped the human brain in conscious patients undergoing brain surgery by the turn of the last century (Morgan 1982 Zimmermann 1982). Neural prostheses have been developed for the central and for the peripheral nervous system. Central neural prostheses in the sense of the present topic are electronic devices that connect to the brain for the purpose of stimulation or detection of activity of the human brain. For obvious reasons, restorative medicine has taken the lead in human electronic implantation. The complete loss of motor function or a sensory channel (e.g. hearing, vision) is a terrible disaster for the individual patient and the bridging of the

The Philosophical Story I

Philosophers and scientists began to speculate intelligently about a wide range of psychological processes, and many of their ideas turned out to be remarkably farsighted. Much of this early imaginative and empirical work was forgotten through the centuries, slowly stumbled on, and rediscovered time and again through careful or serendipitous efforts. In the seventeenth century, John Locke described a clinical procedure for overcoming unusual fears the procedure he set forth is similar to the systematic desensitization method developed this past century by Joseph Wolpe. Similarly, Gustav Fech-ner, founder of psychophysics in the mid-nineteenth century, recognized that the human brain was divided into two parallel hemispheres that were linked by a thin band of connecting fibers, what we now term the corpus collosum. According to his speculations, if the brain was subdivided, it would create two independent realms of consciousness, a speculation confirmed and elaborated in...

Cocaine and Amphetamine Regulated Transcript

Cocaine- and amphetamine-regulated transcript (CART) encodes several putative peptide fragments, some of which decrease feeding upon central administration.36,37 (see ref 38). CART is expressed in numerous brain nuclei, and the actual site of its anorexigenic actions has not yet been fully determined. In the rat LHA, CART is detected in the lion's share of MCH neurons of the zona incerta and medial LHA, whereas most peripeduncular MCH cells do not contain CART.39-40 In contrast, no Hcrt neurons stain for CART.39-40 Notably, according to a preliminary report, some degree of Hcrt CART coexistence can be seen in the human brain.41 This would not be the first example of differential distribution of CART in primate and rodent brain the transcript displays prominent discrepancies in expression e.g. between the human and rat thalamus.42 Coexpression of orexigenic and anorexigenic neuromodulators within the same cell presents an intriguing paradox, which remains to be explained. Further...

Human endogenous retroviruses and multiple sclerosis

Another recent study showed that there is a physiologic expression of an HERV-W Env in human brain that mainly is associated with infiltrating lymphoid cells or brain macrophages, whereas expression of HERV-W Gag antigens is observed in neurons (cell body, axons, dendrites). In contrast to this, an MS-specific Gag and Env pattern was described in which

Iron and Copper Interactions in Mammals and

The biochemical links between dietary copper and iron metabolism in animals that were outlined in physiological terms earlier, have tended to focus on the principal copper-containing protein of plasma, ceruloplasmin. Ceruloplasmin is a blue copper protein synthesized mainly in the liver. In the pioneering studies of the Utah group, dietary copper restriction was reflected in decreased plasma levels of ceruloplasmin, defective mobilization of iron into the plasma with hypoferraemia, and accumulation of iron in parenchymal tissues (Lee et al., 1968). Injection of ceruloplasmin repairs the hypoferraemia (Ragan et al., 1969). It was proposed that it was the ferroxidase activity of ceruloplasmin (Osaki etal., 1966) which was necessary for the oxidation of Fe2+ to Fe3+ to enable its uptake into apotransferrin (Williams etal., 1974). The importance of ceruloplasmin in normal human iron homeostasis has been confirmed by the recent description of the human congenital disease,...

Gene Structure and Expression Studies

Partial RT-PCR products are used as Northern blotting probes. Probes are hybridized to nylon membranes that had been blotted with 40 g of human brain total RNA or 10 g of human hippocampal poly A+ RNA (Clontech, Palo Alto, CA). Human brain RNAs from different region were used as quantitative RT-PCR templates. The ratio between RT-PCR products corresponded to that of iso-forms.

Questions For Future Studies

In conclusion, during the late stage, production of progeny virions is regulated in multiple steps, including transcription, splicing, translation, nuclear transport, and maturation of virions (Fig. 8.9). We have shown in this chapter that JCV has distinctive regulatory mechanism from SV40 and murine polyoma virus. Studies on the underlying molecular mechanisms in the production of progeny virions and their structures can contribute to understanding the nature of JCV and the pathogenesis of PML. Inhibition of critical regulatory steps in the production of progeny virions may provide an efficient therapy for progressive demyelination in the JCV-infected human brain.

The Biology of Emotions

Many scientists contend that it is illogical to believe that emotions appear suddenly in humans. If evolution takes place through the process of natural selection, the emotions found in humans would be present in early evolutionary ancestors. The similarities in brain anatomy and chemistry between animals and humans would then support the idea that some basic emotions exist in various

Image Analysis And Atlases

At the Mouse Imaging Centre, we have developed a variational excised brain atlas in which a number of normal age-, weight-, and sex-matched mice are imaged and then processed to provide an unbiased average atlas and estimates of its variation 47 . A number of tools developed in human brain registration have been adapted for our purposes 48,49 . Figure 5.12 shows our initial results from the averaging together of brains excised from nine 8-week-old, male inbred 129S1 SvImJ mice. We have found the variability in this strain of mice at this particular age to be low. For example, the mean volume and standard deviation of the cerebral cortex and corpus callosum were 109 2 and 13 0.3 mm3, respectively. Since the variability is so small, we believe that our variational atlas can serve as a yardstick against which mutants with anatomical anomalies can be measured.

Vicos Poetic Logic and the Embodiment of Mind

Vico opposed the view of the scholastics and Descartes that human nature is lawful, fixed, static, and unchanging. It is important for us to recognize that his work foreshadowed controversies that are still very much alive today. Although neurobiology has unquestionably demonstrated the plasticity of the human brain, there are those who still argue that human nature has been fixed in its genetic adaptation to a late Pleistocene environment and has therefore remained unchanged for 25,000 years (Tooby and Cosmides 1990). Those who believe in an unchanging human nature also argue for a strong genetic determinism of the mind (Dawkins 1976 and Wilson 1998).

Functional Role Within the Feeding Circuitry

Major target for the arcuate nucleus, which focused on the neuroendocrine and autonomic response to starvation. However, the discovery of AGRP as a selective marker for arcuate nucleus NPY neurons also made it possible to map out the full extent of the projections emanating from these cells. By this approach it was demonstrated not only that the NPY and POMC neurons form almost completely parallel ascending pathways, but also that these extend well beyond the hypothalamus and include a wealth of structures, from the olfactory nuclei to the nucleus tractus solitarii.126 In this manner, the metabolic signals are in a position to directly engage numerous specialized assemblies of neurons to participate in the decision to feed or not to feed. Such a concept of distributed systems has been invoked in systems-oriented models of the regulation of feeding behaviour.127, 103,128,104 The circuitry can be compared to the basal ganglia, where incoming information has been proposed to disseminate...

Changes in Immune Marker Expression in Response to IFN7

Data from rat brain-derived stem cells also show dynamic upregulation of MHC class I in response to rat recombinant IFN-7 38 . In addition, we obtained similar results with human brain-derived stem cells Klassen et al., unpublished data . Although class II levels are high at baseline in the human cells, levels increased even higher after 4-day exposure to human recombinant IFN-7. MHC class II was also expressed at this time, as was the adhesion marker intercellular adhesion molecule (CD54), the latter result being consistent with the behavioral changes (increased flattening of cells and increased adhesion to substrate) seen in culture during this time.


The cerebellum is another specialized portion of the CNS with a highly organized structure. The role of the cerebellum is to coordinate motor actions by comparing what happens in terms of movement with what the CNS intended. The cerebellum has only 10 of the volume of the human brain however, it contains over half the neurons found in the CNS. For example, there are 1011 granular cell neurons in the cerebellum, more than the total number in the cerebral cortex (Ghez, 1991).

The Primate Brain

Because humans are upright, bipedal walkers, the human brain is at the top of the spinal cord rather than somewhat in front of it as in other primates. The human brain weighs only about three pounds, or about 2 percent of the weight of a 150 pound individual, but that is still larger relative to body size than the brains of other primates, even tions, and social interactions take place, although even in monkeys and apes the front of the brain manages social awareness and behavior. Since the primate brains of apes and monkeys are so similar to those of humans, many studies of brain function have involved experimentation on these animals, humans' closest relatives. Other mammals such as mice, rats, cats, and dogs have also served as subjects of brain studies that can be related not only to their own specific behavior, but also to how the human brain works in its various component parts. Since neurons are very similar to each other, whether they come from sea slugs, squid, or mammals,...

Neuronal Circuits

As well as these questions of basic neurotransmitters and receptors, it has become clear that the circuitry of the neurons may also be abnormal in patients with epilepsy (75-87). There is a form of reorganization, characterized by sprouting of axonal branches and terminals, that occurs as a result of seizures in human hippocampal tissue as well as in animal models (88, 89). Most of these studies show concurrent loss of cells associated with this axonal sprouting. It has been suggested that the sprouting axons replace the neurons at the synaptic sites where cell death has removed the presynaptic elements. This process appears to provide cells with additional recurrent excitatory feedback that can increase the excitability of the circuits. The discovery that neurogenesis can occur in the human brain has led to the idea that cellular proliferation (in addition to cell loss) may be part of the plastic process underlying epileptogenesis.


Aleshin AE, Zeng C, Bourenkov GP, Bartunik HD, Fromm HJ, Honzatko RB (1998) The mechanism of regulation of hexokinase new insights from the crystal structure of recombinant human brain hexokinase complexed with glucose and glucose 6-phosphate. Structure 6(1) 39-50 Bennet WSJ, Steitz TA (1980) Structure of a complex between yeast hexokinase A and glucose structure determination and refinement at 3.5 A resolution. J Mol Biol 140(2) 183-209 Gryczynski Z, Gryczynski I, Lakowicz JR (2000) Simple apparatus for polarization sensing of analytes. Opt Eng 39 2351-2358 Honzatko RB, Aleshin AE, Zeng C, Bartunik HD, Fromm HJ (1998) Regulation of hexokinase I crystal structure of recombinant human brain hexokinase com-plexed with glucose and phosphate. J Mol Biol 282(2) 345-357 Ishikawa H, Maeda T, Hikita H (1987) Initial-rate studies of a thermophilic glucokinase from Bacillus stearo-thermophilus. Biochem J 248 13-20 Jaenicke R Schuring H Beaucamp N, Ostendorp R (1996) Structure and stability of...


It is not unlikely that clinical neuroscience is rapidly entering an era of experimental cellular and molecular neurosurgery. In particular, stem cell and gene technology are rapidly progressing fields in medical science, which are likely to make restorative interventions possible and will, therefore, also be embraced quickly for the development of new therapeutic strategies in human brain dysfunctions. Newspapers and broadcast media frequently report on these developments and the use of human ESCs for organ repair is presently a topic of worldwide debate as well as of ethical concern on the political agendas11,12. The CNS, however, is a structurally Whereas cellular and molecular surgical interventions are developed and experimentally investigated in clinical trials for the cure of neu-rodegenerative conditions and the effects of trauma in the human brain, they are also often discussed as interventions for psychiatric disorders. In particular, gene transfer has been proposed as a...


The adult brain is a morphologically heterogeneous organ of complex networks of short and long distance interconnected nerve cells, grouped in nuclei or layers and acting in one or several neuronal circuits using nerve cell type-specific chemical messengers for communication (neurotransmission). With its vast array of connections of cellular trees of neu-rites and axons, the brain is too complex a structure to be compared with a computer, whose modules can be replaced in the case of a defect. The integration of new nerve cells requires the use of immature neurons for grafting, as mature nerve cells are unable to survive transplantation and integrate in adult neuronal networks. Immature nerve cells can either be obtained directly from the abortion remains of human embryos, or indirectly in two ways i) by in vitro proliferation and or differentiation of human stem and germ cells towards a neuronal phenotype, or ii) by differentiation of cell lines of neural precursor...


Neural networks were originally conceived as computational models of the way in which the human brain works. Like the human brain, they consist of many units (analogous to neurons and sometimes called by the same name) connected to each other by variable strength links (analogous to axons in the brain). These variable strength links are abstract representations of the way that most neurons actually communicate with each other in the brain through changes in the rate or frequency of electrical or chemical messages. As with a number of the techniques described in this book, this technique has been inspired by the way biological organisms (in particular humans) solve the problems of computation in nature. As mathematical models, they have found a large number of applications in science and commerce, particularly in the area of finance and market prediction. The attraction of neural networks is that they can 'learn' relationships between sets of variables taken from a system. Once...


The central role of glucose in metabolism arose early in evolution, and this sugar remains the nearly universal fuel and building block in modern organisms, from microbes to humans. In mammals, some tissues depend almost completely on glucose for their metabolic energy. For the human brain and nervous system, as well as the erythrocytes, testes, renal medulla, and embryonic tissues, glucose from the blood is the sole or major fuel source. The brain alone requires about 120 g of glucose each day more than half of all the glucose stored as glycogen in muscle and liver. However, the supply of glucose from these stores is not always sufficient between meals and during longer fasts, or after vigorous exercise, glycogen is depleted. For these times, organisms need a method for synthesizing glucose from noncar-bohydrate precursors. This is accomplished by a pathway called gluconeogenesis (formation of new sugar), which converts pyruvate and related three- and four-carbon compounds to glucose.


At long-term, our better knowledge of the functional crosstalk between neurons and glia in health and disease and the bidirectional flux of immune cells from the peripheral blood to the brain parenchyma through the blood-brain barrier will allow the build-up of new tools for the treatment of the major diseases afflicting the human brain. In this chapter we review and discuss the immune response of the brain to injury, on the basis of the close interaction between excitotoxicity and inflammation.

Semantic Nets

Semantic nets were designed in the 1960s to model the storage of knowledge in the human brain. They tried to represent every fact separately and to connect all facts that are in some sense connected. The model of associative memory was designed using an oriented graph, called semantic network. The nodes of this graph represented words in natural language and the edges represented associations and meanings between two terms in a language. It can be generally stated that a semantic network simply offers a graphical notation for logical formulas restricted to unary and binary predicates and the two types of quantification is

The fMRI Experiment

FMRI employs rapid imaging techniques that yield a low signal-to-noise ratio (SNR). The functional effects are of the order of the signal stability in the human brain (1.5 to 5 at 1.5 T), and therefore the functional effects cannot be recognized on a single volume. For this reason, an fMRI experiment acquires many volumes during at least two different experimental conditions. Usually, the effects are detected by an analysis of the corresponding voxel on all volumes. Therefore, it is necessary that the subject's brain remains in the same position during the entire

Data Analysis

In the case of a localization study, the results of investigations in a group of subjects must be matched. In order to map the activated areas onto a particular anatomical region of the cortex, these areas are registered to a standard atlas of the human brain (e.g., the Talairach atlas Talairach and Tournoux, 1988), or onto the 3D data set of the individual brain. In this way the results of different studies of the same or distinct modalities can be compared (Apicella et al., 1989 Pellizari et al., 1989). A more sophisticated display method uses flat maps (Dale and Sereno, 1993 Carman et al., 1995), whereby the creased surface of the cortex is unfolded onto a flat 2D plane onto which the functional results are then mapped. This method is especially useful for visualizing a retinotopy when investigating the visual cortex.

Medical Background

The brain basically consists of two types of tissue grey matter and white matter. Grey matter is composed of neuronal and glial cell bodies that control brain activity while the cortex (like the 'bark') is a coat of grey matter that covers the brain. White matter fibre tracts are myelinated neuron axon bundles located throughout the inner regions of the brain. These fibres establish pathways between grey matter regions. The corpus callosum is a thick band of white matter fibres connecting the left and right cerebral hemispheres of the brain. Within each hemisphere, there are several white matter pathways connecting the cortex to the nuclei deep within the brain see Figure 11.2. Figure 11.3 shows two photographs of a human brain showing grey and white matter distribution and the corpus collosum. Figure 11.2. Two cross-sections of a human brain showing fibrous white matter and the corpus callosum which connects the left and right cerebral hemispheres. (Figure courtesy of Dr. E.C....

Magnetic Stimulation

Magnetic nerve stimulation, which has been studied for over a century, was first reported for the human brain by Barker et al. (1985). Since that time, significant advances have continued to be made, and today magnetic nerve stimulation is used widely both in neurophysiological studies and for clinical diagnoses. Recently, a method of focal and vectorial stimulation of the human brain was developed. This section provides an overview of the early attempts at, and more recent developments in, transcranial magnetic stimulation (TMS), together with details of the present status of the technique. After introducing the historical, technical and physiological principles and basic mechanisms of the method, a representative case of the use of TMS is described. There then follows a discussion of how human cortical function can be modified by magnetic stimulation, and how this might be used therapeutically in neurological disorders.

Uses of stem cells

Examples in the literature of the production of this type of chimera for experimental purposes. These include the production of a human hematopoietic system after bone marrow transplantation in the fetal sheep and the investigation of the neurogenic potential of human neural stem cells transplanted into the fetal mouse brain. A concern that has been raised about the production of this type of chimera is one regarding the possible induction of human qualities in the recipient animal. The two primary concerns are higher level neurological function and the appearance of recognizable human features. For most, the more worrisome of these two possibilities is the development of human-like intelligence, consciousness, or emotion. Fortunately, this is highly unlikely. Many of the critical developmental signals for the formation of the human brain will have already occurred or signaling necessary for a developing human nervous system will be absent in the developing animal nervous system....


Lippincott Radiology 101

CT scan of a normal adult human brain. (Reprinted with permission from Erkonen WE, Smith WL. Radiology 101 Basics and Fundamentals of Imaging. Philadelphia Lippincott Williams & Wilkins, 1998.) FIGURE 7-7. CT scan of a normal adult human brain. (Reprinted with permission from Erkonen WE, Smith WL. Radiology 101 Basics and Fundamentals of Imaging. Philadelphia Lippincott Williams & Wilkins, 1998.)

Comparative Studies

In the human brain, Hcrt-immunoreactive neurons are localized to the perifornical area and DMH, with few neurons seen in the LHA12,43 and Hcrt-immunoreactive axons are as widespread as those seen in rodents (see Section 6). In the monkey hypothalamus, the location of Hcrt neurons and the distribution of Hcrt axons is roughly similar to that seen in the rat, with Hcrt-immunoreactive neurons in the perifornical area and LHA and, to a lesser extent, in the DMH.44 In the cat brain, Hcrt-1-immunoreactive neurons are present in the tuberal hypothalamus and have a roughly similar distribution to that seen in rodents, with the greatest concentrations of neurons seen dorsal and lateral to the fornix, although the neurons are slightly more widely scattered than in the rat with several neurons extending in the medial direction to the periventricular region and a few neurons as far ventral as the arcuate nucleus.45,46 In the sheep hypothalamus, the distribution of Hcrt1-immunoreactive neurons...

Cranial Meningocele

Meningocele Cranial Intranasal

CT has a complementary role, related to its superior depiction of bony detail. At MR, the cephalocele appears as a round mass with sharp margins, isointense to CSF in all sequences (meningocele) or containing some tissue isointense to brain parenchyma (meningoencephalocele), protruding from the in-tracranial cavity into the nasal cavity or paranasal sinuses. The lumen of the lesion is continuous with the subarachnoid space and often has a constriction in the portion passing through the bone defect (the neck of the cephalocele) (Fig. 7.7). CT clearly shows the sclerotic margins of the bone defect. Cerebral MR may show the associated brain anatomy distortion, presumably due to the effect of the brain pulsation in utero, which pushed the pliable unmyelinated brain outward through the defect (Truwit et al. 1996). The result is a general tendency of the ventricles and subarachnoid spaces, which subtend the cephalocele, to be stretched and elongated, pointing toward the calvarial defect....

Stria Medullaris

Stria Medullaris Thalami

The cortical and subcortical structures of the limbic system extending from the cerebral cortex to the dien-cephalon. The fiber tracts that interconnect the structures of the limbic system are also shown. (Modified from Truex RC, Carpenter MB. Strong and Elwyn's Human Neuroanatomy. 5th Ed. Baltimore Williams & Wilkins, 1964.) The origins and projections of the three major dopaminergic systems. (Modified from Heimer L. The Human Brain and Spinal Cord. New York Springer-Verlag, 1983.) The origins and projections of the three major dopaminergic systems. (Modified from Heimer L. The Human Brain and Spinal Cord. New York Springer-Verlag, 1983.) The origins and projections of five of seven cell groups of noradrenergic neurons of the brain. The depicted groups originate in the medulla and pons. Among the latter, the locus ceruleus in the dorsal pons innervates most parts of the CNS. (Modified from Heimer L. The Human Brain and Spinal Cord. New York Springer-Verlag, 1983.) The origins and...

Chapter Fortysix

Wernicke Brocas And Primary Areas

This chapter has only scratched the surface of our knowledge about the organization and functions of the human brain, but it may give you some idea of the incredible challenge that neurobiologists face in trying to understand their own brains. Progress is being aided by powerful new technologies such as patch clamping (see Figure 44.11), functional imaging, and neurochemical and molecular methods. However, even these sophisticated new research tools may not allow us to answer the question What is consciousness


In the preceding decades, clinical, as well as theoretical, neuroscience has developed a wide array of methods for intervening in the mental or psychic life of human beings. By and large, these new forms of intervention diverge from (most of) the classical means of intervention in that they are exclusively physiological in nature. That is to say they work directly upon the central nervous system (CNS) and, in particular, the human brain. It is possible to distinguish four main types of physiological intervention genetic, pharmacologic, electro-magnetic, and surgical (cf. Farah 2005 35-36 Glannon 2006b 43-52)162 The latter may be differentiated further into four subclasses (i) the implantation of neuroprostheses, including brain-computer interfaces (so-called bionics), (ii) the intracranial grafting or implantation of cells (neural, non-neural, or embryonic stem cells) for tissue repair or cell-containing devices for the local delivery of bioactive compounds, (iii) intracranial gene...

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