Interaction of the Nuclear Spin with Magnetic Fields

MRI requires that the signal-generating protons be placed in a strong static magnetic field. It is conventional to denote the applied magnetic field by a vector quantity, B0. The typical magnetic field strength used in brain imaging is 1.5 T (approximately 30,000 times stronger than the earth's magnetic field). The spatial Figure 1 Key concepts related to MRI signal creation. Figure 1 Key concepts related to MRI signal creation. homogeneity of the magnetic field also plays an important role in...

Other Muscular Pain Conditions

Biofeedback from other tense muscle sites (low back, head, shoulders, neck) has also been shown to be clinically useful. Typically patients use relaxation techniques in conjunction with EMG feedback to reduce the sensations of pain or tension. Work by David Hubbard and the author has shown that this is probably due to a reduction in sympathetic flow to muscle spindles rather than to a reduction of voluntary muscle action potentials, but more needs to be done to elucidate the exact mechanism or...

Animal Models of Brain Degeneration in Parkinsons Disease

Among the chronic brain degenerative diseases, PD has the best characterized and most consistent models. Although the underlying mechanism of disease in these models may be significantly different from the human condition, they reproduce rather closely the pathology in the final stages of dopaminergic degeneration in PD and constitute a crucial basis to test novel therapies. Due to its well-defined neuroanatomical distribution, the nigrostriatal dopaminergic pathway can be le-sioned or severed...

Dopamine And Learning

Animal research shows that dopamine is involved in the acquisition of operant tasks, avoidance learning, and intracranial self-stimulation. It is thought that dopamine in mesolimbic regions (most notably the nucleus accumbens) is involved in both the acquisition and the maintenance of these behaviors. This conclusion was based primarily on results from studies using dopamine-depleting agents and dopaminergic drugs to evaluate their effects on acquisition or maintenance of reinforced behaviors....

Transduction Process in Cochlear Hair Cells

Stereocilia of IHCs are in functional contact with an overlying auxiliary structure called the tectorial membrane. The base of the hair cell is in synaptic contact with the distal ends of auditory nerve axons. Sound waves that reach the inner ear set the basilar membrane, and hence the organ of Corti, into motion. This causes a shearing motion between the tectorial membrane and the tops of the hair cells that, in turn, displaces the stereocilia and triggers the flow of transducer currents....

Neuropsychological Studies Of Category Learning

One approach that has successfully demonstrated implicit learning of categories is the use of data from amnesic patients. The fact that amnesic patients are able to exhibit normal category learning in several paradigms suggests that implicit learning can support normal performance. In addition to their intact performance on artificial grammar tasks described previously, amnesic patients have been shown to perform normally on category learning based on similarity to a prototype, category...

Control of Pupil Size

Our pupils become larger when we move to a darker environment, and they constrict again when we move back into the light. This light reflex is mediated via contraction and relaxation of the sphincter pupillae muscle, innervated by parasympathetic final motorneurons located in the ciliary ganglia behind the eyeballs. In turn, the final motoneurons are regulated via inputs from brain stem parasympathetic moto-neurons in the Edinger-Westfal subdivision of the oculomotor (cranial III) nucleus...

Mechanical Motion in the Inner Ear in Response to Sound

The basilar membrane is a resonant structure varying systematically in width and stiffness. It is wider (0.420.65 mm) and more flaccid at the cochlear apex than at the base (0.08-0.16 mm). When a sound wave is transmitted to the fluid of the inner ear, the basilar membrane is set in motion. Basilar membrane motion is best described as a traveling wave of deformation, which begins at the cochlear base and moves apically toward a frequency-dependent place of maximal amplitude (Fig. 4). When very...

Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE), also known simply as lupus, is a multisystem disease with protean clinical manifestations. When SLE affects the brain, causing what has been variously known as lupus cerebritis or neuropsychiatric lupus, a wide range of neurobehavioral features may follow. In many cases, multifocal white matter lesions are seen on brain MRI that likely represent ischemic lesions and infarcts related to the vasculopathy that is characteristic of SLE. Treatment often includes...

Feedback From Brain Waves

One of the first applications of biofeedback occurred in the 1960s when a great deal of interest in altered states of consciousness arose. A number of researchers in California used newly acquired knowledge from sleep research to study the encephalographic (EEG) aspects of meditative states. It was observed that calm, transcendent states were accompanied by a predominance of a rhythm (8-12 Hz or cycles per second) activity. Biofeedback of this activity was accomplished by providing a tone or...

Lewy Body Variant LBV of AD

The Lewy body variant of AD (sometimes also referred to as common DLB, in contrast to pure DLB) is characterized by the typical neuritic plaques and neurofibrillary tangles of AD, the subcortical changes of PD, and the presence of diffusely distributed cortical Lewy bodies. Persons with the LBV of AD, compared to persons with pure AD, show a greater proportion of mild parkinsonian or other extrapyramidal motor findings, a typically fluctuating cognitive impairment, visual or auditory...

Nonpharmacological Treatment

Nonpharmacological treatments include behavioral methods and psychological treatment. Behavioral methods include biofeedback, relaxation techniques, and reinforcement of maintaining a regular schedule, exercise, healthy diet, and regular sleep. There are several modalities of biofeedback one can monitor body temperature on electromyography. The final goal is the same the extinction of pain behavior. Relaxation techniques include progressive muscle relaxation and imaginary- and suggestion-based...

Parkinsons Disease PD

PD is primarily a progressive, extrapyramidal (involving motor systems ofthe basal ganglia rather than the pyramidal tract) disorder with clinical motor features of stooped posture, bradykinesia (slowing of movement initiation), tremor (when the affected limb is at rest, but typically not during movement), cogwheel rigidity (i.e., rigidity that seems to catch and release, much like a cogwheel, when the clinician attempts to passively move the patient's limb), and festinating gait. Dementia has...

Etiology

In 1862, William John Little, an orthopedic surgeon, was the first to address and hypothesize on the etiology of CP. Little described developmental motor abnormalities in children as spastic rigidity.'' He hypothesized that prolonged premature labor, breech delivery, or birth asphyxia were the causes of cerebral damage resulting in impairments in posture and movement. However, since the 1860s, discussion has continued regarding the exact cause of CP because the clinical manifestations of the...

Therapeutic Interventions

The understanding that the autoimmune disease is caused by an immune response directed against self points to possible modes of therapeutic interventions. Following this understanding, it was possible to 1. Blocking MHC class II molecules By antibodies that are specific to the MHC or to the complex of particular MHC molecules with the pathogenic peptide embedded in its binding groove. Using peptides that bind the MHC and do not activate the pathogenic T cells thus, the peptides block the...

Learning and Memory

For some time, a division between the anatomical structures involved in declarative memory and those involved in procedural memory has been proposed. Declarative memory involves the ability to learn facts or items that can be deliberately recalled procedural learning involves the ability to master a set of procedures to perform a specific task. Procedural memory has been explored primarily in patients with degenerative diseases of the basal ganglia (i.e., Huntington's and Parkinson's diseases)....

Down Syndrome

Down syndrome (DS) is easily recognized by the lay population and perhaps thought to be synonymous with mental retardation. It is one of the most common genetic causes of mental retardation and perhaps the best known. It is estimated that DS occurs about 1 to 1.5 times every 1000 births. However, other estimates reveal DS may occur once in every 600 births. The risk of having a child with DS increases as the age of the mother increases. It is estimated that males are affected slightly more than...

Visual System

The primary visual cortex (Brodmann area 17) is located in and on either side of the calcarine sulcus, on the medial surface of the occipital lobe. It functions primarily in discerning the intensity, shape, size, and location of objects in the visual field. As with other cortical areas, the primary visual cortex is composed of six layers. Visual input from the lateral geniculate nucleus of the thalamus terminates primarily in layer 4. This input is then relayed through layers 2 and 3 to...

Neuroimaging Studies Of Category Learning

Functional magnetic resonance imaging (fMRI) studies also support the idea that there are multiple forms of categorization that depend on different brain systems. Application of explicit rules appears to activate frontal and parietal regions involved in working memory and selective attention. When nonverbal rules appear to guide responses, as in the probabilistic classification task described previously, activation has been reported in the caudate nucleus. Interestingly, this neostriatal...

Treatment And Prevention Of Neurocognitive Complications

The extent to which antiretroviral therapy protects against neurocognitive complications remains uncertain. Historical data indicate that the advent of the first antiretroviral (AZT) was associated with reduction in diagnosis of AIDS-associated dementia. However, not all investigators have reached the same conclusion. The advent of potent antiretroviral combination therapies holds with it the promise of reducing viral load to unmeasurable or very low levels. Studies are under way to determine...

Relaxation

The signal thus generated decays exponentially over time due to a number of processes. If the raw, exponential decay of the signal is measured (without doing anything else to create images), the process takes about 100 msec and the exponential time constant associated with that decay is conventionally called T2* (read tee-two-star). This decay in the measured signal is driven by a number of different physical processes. First, the protons slowly (on the time scale of seconds for most brain...

Control of Vertical Gaze in the Midbrain

A rostral portion of the midbrain reticular formation adjacent to the periaqueductal gray (riMLF) contains neurons whose primary on-directions are related to vertical gaze (combined head and eye movements), as do regions near the interstitial nucleus of Cajal (Fig. 1C). These burst neurons (both excitatory and inhibitory) fire during every vertical or torsional saccadic eye movement as well as during the quick phases of vertical, vestibularly induced nystagmus. Efferent projections from the...

Spectral Profiles

The spectrum of the sound from one source will differ from that of another source. Experiments in spectral profile analysis measure the auditory system's sensitivity to changes in the amplitudes of the spectral components of a complex sound. The schematic diagrams on the bottom of Fig. 16 display different spectra used in a spectral profile experiment. The spectra consist of several tonal components logarithmically spaced in frequency. As can be seen, the center Figure 15 Both the basic MDI...

Vasodilation and Constriction

It appears that humans (and animals) can regulate vasodilatation and vasoconstriction. Robert Freeman and his colleagues have carefully worked out the mechanisms in finger blood regulation using biofeedback training procedures. First, they demonstrated that volunteers could warm or cool their hands upon command. Then they used a series of pharmacological blockades to show that the ability to cool one's fingers is mediated by the sympathetic nerve, but warming above baseline temperature is...

B GABA as a Paracrine Reset Signal

GABA-producing cells increase GAD67 and GAD67 mRNA levels in response to injury, whereas GAD65 and its mRNA are usually unchanged. Injuries that produce increased GAD67 include chemical lesions of the substantia nigra and hippocampus, neuroleptic drugs, spinal cord transection, and acute stress. The increase in GAD67 can be observed as soon as 1 hr after insult, implicating immediate early genes in GAD67 regulation. Most GAD67 is not associated with synapses, and GAD67 may be responsible for...

Pharmacological Intervention A Oral Medications

In the 1990s, Albright reported that oral medications, including benzodiazepines and skeletal muscle relaxants, had been used with limited success to diminish the effects of spasticity. Diazepam, a benzodiazepine, facilitates the inhibitory response of g-aminobutyric acid (GABA) neurotransmitters by increasing the conductance of chloride ions upon binding to GABAa receptors. This results in a presynaptic inhibition at the spinal cord level with resultant relaxation of skeletal muscle. Use of...

Pathways That Determine Neuronal Injury

Despite the immediate event, such as cardiac arrest or cerebral trauma, that may ultimately result in organic brain disease, specific cellular signal transduction pathways in the central nervous system ultimately influence the extent of neuronal injury. However, one must remember that it is multiple mechanisms, rather than a single cellular pathway, that determine neuronal survival during organic brain disease. Although neuronal injury associated with several disease entities, such as stroke,...

Other Autonomic Biofeedback Methods

A few other types of feedback have been reported that seem to indicate learned regulation of the ANS. Some reports of control of sweat gland activity at the extremities appear credible. Hyperhydrosis is a disorder of excessive sweating. Biofeedback is used, with the signal usually taken from the palms of the hands, to reduce excessive activity. Whether the reduction is an example of direct autonomic control or is secondary to learning to dampen the sympathetic response is not known. Biofeedback...

Suggested Reading

G., and Bernston, G. G. (Eds.) (2000). Handbook of Psychophysiology, 2nd ed. Cambridge University Press, Cambridge, UK. Porges, S. (1997) Emotion An evolutionary byproduct of neural regulation of the autonomic nervous system. In The Integrative Neurology of Affiliation (C. S. Carter, I. Lederhendler, and B. Kirkpatrick, Eds.), 807. New York Academy of Science. Schwartz, M. S. (1995). Biofeedback A Practitioners Guide, 2nd ed. Guilford Press, New York.

Rehabilitation

Neuromuscular rehabilitation centers have used EMG biofeedback to successfully aid physical therapy and occupational therapy procedures with stroke, spinal cord, head injury, and various neuromuscular disorder patients. Typically, the feedback is used with stimulation and exercises to recruit neuromuscular pathways that are not up to par. It is hard to pin down the components in this protocol. It may improve patient motivation, reopen neural pathways, help regulate motor homeostasis, or all of...

Xenografts in Parkinsons Disease

Human xenografts have been used in animal models to study principles of neurotransplantation or mechanisms of brain degeneration. More often, xenotransplantation has been tested with the goal to explore alternative sources of mesencephalic fetal tissues for grafting into the degenerating brain. Studies using porcine fetal cells in rats showed that the grafts survived and integrated successfully in the host. Currently, there are several ongoing clinical trials to assess the feasibility of...

Other Causes of Stroke

There are many other causes of stroke, most of which are rare. Inflammatory disorders can cause thickening of the vessel walls, with obstruction of blood flow, hemorrhage, and multifocal infarction. There are several forms of angiitis or vasculitis (Table II), including Moyamoya disease, Wegener's granulomatosis, and polyarteritis nodosa. Some forms of vascular disease are notoriously difficult to diagnose, and the vascular pathology is poorly understood (e.g., the vasculopathy of systemic...

Surgical Strategies A Preoperative

The preoperative investigation of patients with cerebral lesions falls into two general categories. The first is targeting areas for the purpose of stimulation or ablation. These circumstances occur in patients with movement disorders in which parts of the basal ganglia or other subcortical regions are selected for lesioning (e.g., pallidotomy) as a means of improving symptoms. Lesioning using stereotactic focal radiation or direct surgical ablation, by heating or freezing, are of interest for...

Motor Functions and Movement Programs

Given the motor symptoms of Huntington's and Parkinson's diseases and the major involvement of the basal ganglia in these disorders, the involvement of the basal ganglia in movement has been taken for granted. Huntington's disease is an autosomal-dominant genetic disorder characterized by choreiform movements (i.e., involuntary movements that resemble segments of voluntary movements). In the early stages of Huntington's disease, cell loss is obvious in the head of the caudate nucleus, but as...

Auditory Nerve

Each auditory nerve fiber in the auditory portion of the VIII cranial nerve innervates a small number of inner hair cells, with nerve fibers near the center of the auditory nerve bundle coming from the cochlear apex and those on the outside of the bundle coming from the cochlear base. Thus, the fibers in the auditory nerve bundle are topographically organized on the basis of their cochlear innervation, and they transmit the neural code for sound from the cochlea to the cochlear nucleus in the...

Plasticity And Reorganization

In the past several years, much research has revealed that the functional characteristics of the auditory cortex are not necessarily static but instead may be influenced by environmental experience. It has been shown that many properties of cortical neurons may change as a function of such experience, and that reorganization may occur when there is a change in the normal sensory input. The most dramatic changes in auditory cortex organization are evident when there is loss of a sensory...

Neurological Substrate Of The Disorder

The damage responsible for these disorders is usually caused by cerebrovascular disease, usually embolic stroke, that involves the midportion of the first temporal gyrus bilaterally (at least one case has been reportedly caused by a hemorrhage in an auditory structure in the brain stem, the inferior colliculi). If caused by unilateral damage, the lesion is usually deep in the posterior temporal lobe of the hemisphere dominant for speech (usually the left hemisphere). In such cases, there may be...

Host Characteristics

The age of the patient is also a factor in the severity of neurobehavioral deficits. The incidence of histopa-thologically more aggressive tumors, such as glioblas-toma multiforme, increases with age. However, histopathologically less malignant tumors, such as anaplastic astrocytoma, also behave more aggressively in the older patient. Older patients are also at higher risk for having other concurrent neurodegenerative illnesses, such as Parkinson's disease or vascular disease. Finally, very old...

Psychosocial and Environmental Factors in Recovery of Function

Family support, mood, the environment, resistance to change, the attitudes of the rehabilitation professionals, and hope and expectations for recovery are some of the factors related to recovery. These factors appear to be intimately related to neurotransmitters and to the effectiveness of rehabilitation programs. The type of physical environment in which the brain-damaged person is placed may be closely related to the recovery. The most important functional gains in the animal model of...

Future Directions

The major force in the introduction of new and effective treatment for autoimmune diseases is our enhanced understanding of immunology in general and control of immune cell activation in particular. As we discover the key players in T cell activation and the molecular tools to abort an immune response in its early stages without adversely affecting the millions of other beneficial immune cells, we will be able to introduce novel and more effective treatments. Since these diseases cause...

Progressive Supranuclear Palsy PSP

PSP is also known as Steele-Richardson-Olszewski syndrome. It is a degenerative disorder of subcortical nuclei, including the subthalamic nucleus, substantia nigra, globus pallidus, caudate, putamen, and peria-queductal gray. Clinically, persons with PSP show paralysis involving motor neurons of the eye, leading to impaired downward ocular gaze and other ocular symptoms. Clinical diagnosis requires documentation of at least two of the following signs axial dystonia (abnormal pattern of muscle...

Localization Of Function

The term functional localization is used to indicate that certain functions can be localized to particular areas of the cerebral cortex. The mapping of cortical function began with inferences made from the deficits produced by cortical lesions in humans. Subsequently, techniques such as single-cell recording and electrical stimulation of cells in the cerebral cortex have been used in animals, nonhuman primates, as well as humans undergoing surgery for diseases such as epilepsy and Parkinson's...

Types Of Eventrelated Potentials

Model-based source localization, computational decomposition of complex responses, and quantitative estimates of the activation time courses of identified brain regions are all relatively new tools for the analysis of event-related neural electromagnetic data. However, 50 years of macroscopic electrophysiologi- cal study ofneurological, psychological, cognitive, and behavioral processes of the human brain have produced a rich legacy of experimental observations and interpretation. Many of these...

Disorders of Higher Brain Regions Associated with Hallucinations

Hallucinations are also associated with primary pathology at higher levels of the brain. Most prominent in this category are those that occur in migraine, epilepsy, and schizophrenia. Investigation of cerebral activity associated with hallucinations in these settings has been aided in recent years by the development of techniques such as electroencephalography (EEG), evoked potentials, single photon emission computed tomography (SPECT), positron emission tomography (PET), and functional...

Epidemiology Of Mood Disorders

Epidemiology is the study of the distribution of a disease or condition in a population and of the factors that influence this distribution. Due to the high prevalence and morbidity of mood disorders for which effective treatment is available, there has been growing interest in recent years in assessing the epidemiological distribution of these disorders. Results from the National Comorbidity Survey (NCS) show that mood disorders, along with simple phobia and alcohol dependence, are the most...

Laterality In Nonhuman Species

Behavioral and biological laterality is also ubiquitous in many nonhuman species, with many instances of asymmetry being at least analogous to asymmetries found in humans. At least some may also be homologous, in the sense of sharing common structures and developmental origins. Here, I review some of the most well-established laterality effects in other species and note their relationship to human laterality. Motor asymmetries have been discovered for a number of species, with individuals...

Diversity in Living Brains Cladistics

Having emphasized uniformities so forcefully, I must warn against underestimating the importance of diversity. All brains are different, and there are major differences both within and between species. Differences in brains within species are often difficult to measure with conventional anatomical and physiological methods, but since the brain is the control system for behavior, behavioral differences are evidence of differences among brains. Differences among species, of course, are much more...

The Brain And Behavior

The brain relays an enormous number of incoming and outgoing impulses every second. Input may stem from any of our senses, such as hearing, seeing, or feeling. More profound, and considered by the brain to be more important, information may result in the perceptions being stored as memories. These memories may be retrieved and perhaps used while processing subsequent incoming impulses. The result of this processing may be either rather simplified and stereotypical actions, such as reflexes (the...

Psychiatric And Social Aspects Of Epilepsy

A person with epilepsy, particularly if seizures are not immediately controlled, carries an increased risk of developing psychiatric complications. These may be related to the psychological burden of a disorder that is characterized by unpredictable loss of control and is often stigmatized in modern societies. Other risk factors are biological and include the consequences of recurrent epileptic cerebral dysfunction as well as the potentially negative psychotropic effects of AEDs. Psychoses in...

Functional Organization

Our understanding of the functional organization of the human brain has blossomed as never before thanks to the development of neuroimaging technologies that allow direct observation of the patterns of brain activity in human subjects actively engaged in sensory, motor, or cognitive tasks. In conjunction with more traditional electrophysiological, clinical, and psycho-physical approaches, we now are developing a detailed picture of the topography of different visual areas and are beginning to...

Experimental Methodologies

Ongoing spontaneous activity can be recorded at the surface of the human head using MEG or EEG. Such activity typically is characterized by regions of relatively large amplitude oscillatory patterns that vary as a function of position on the head and state of the subject. Pathological responses such as certain forms of slow oscillation or the spikes and waves associated with epileptic activity often can be clearly resolved in the ongoing EEG record. The signals associated with responses to...

Basic Properties Of Microglia A Microglia in the Normal CNS

The CNS is composed of neurons and a nonneuronal population of cells, designated glia, that includes astrocytes, oligodendrocytes, and microglia. del Rio Hortega discovered microglia in 1919 when he developed the silver carbonate methology. He identified process-bearing cells in the CNS parenchyma and named these cells microglia. Microglia contribute to about 10 of the total glial cell population in the CNS of adults. In the 1960s, the existence of ramified microglia as a distinct glial...

Clinical Presentation

Untreated or progressive cerebral herniation can result in increased morbidity and mortality rates. For example, in cases of fulminant hepatocellular failure, cerebral herniation is the leading cause of death and disability. Even in controlled environments such as the operating room, cerebral herniation can be the primary cause of death in approximately 15 of patients. Patients with elevated intracranial pressure resulting in cerebral herniation require a detailed physical and neurologic...

See Also the Following Articles

BRAIN ANATOMY AND NETWORKS NERVOUS SYSTEM, ORGANIZATION OF NEUROANATOMY PERIPHERAL NERVOUS SYSTEM Butler, A. B., andHodos, W. (1996). Comparative Vertebrate Neuroanatomy Evolution and Adaptation. Wiley-Liss, New York. Gilland, E., and Baker, R. (1993). Conservation of neuroepithelial and mesodermal segments in the embryonic vertebrate head. ActaAnat. 148, 110-123. Haines, D. E. (1997). Fundamental Neuroscience. Churchill-Livingstone, New York. Liem, K. F., Bemis, W. E., Walker, W.F., Jr., and...

Dialysis Disequilibrium

The abrupt onset of neurologic symptoms following hemodialysis has been attributed to cerebral edema. Although much speculation focuses on differential fluid shifts related to a rapid decrease in blood urea nitrogen, the specific cause of this osmotic edema remains controversial. A reverse urea effect theorizes that the BBB prevents urea concentrations in the brain from decreasing with serum levels during and immediately following dialysis. A relative hyperosmolar state within the brain...

Large Extracranial Artery Diseases and Stroke

Aortic arch atheromatous plaque thickness directly relates to the risk of stroke. The recurrence rate for stroke is 11.9 per 100 person years when aortic wall thickness reaches 4 mm, in comparison to 3.5 per 100 person years in patients with aortic wall thickness less than 4 mm. Transesophageal echocardiography has substantially improved the detection of aortic arch disease, which had previously been very difficult to assess without angiography. Extracranial carotid artery disease is an...

Intracranial Pressure Monitoring

ICP elevation can infer the presence of cerebral edema. Symptoms of elevated ICP include headache, nausea, vomiting, and altered level of consciousness, which may be superimposed on focal neurologic deficits. When ICP reaches a critical threshold, herniation syndromes may ensue. The initial presentation of this clinical scenario demands an emergent CT scan of the head to identify the underlying process and assess the degree of parenchymal injury. Although neuroimaging methods routinely diagnose...

Migraine with and without Aura

Migraine has a strong genetic component. In a Danish population-based survey of migraine using IHS criteria, the sex- and age-standardized risk of suffering from migraine with aura and migraine without aura among first-degree relatives was 1.9 (95 CI, 1.6-2.2) and 1.4 (95 CI, 1.0-1.8), respectively. This suggests that migraine without aura is caused by a combination of genetic and environmental factors, whereas migraine with aura is more heavily influenced by genetic factors. Proposed modes of...

Status Epilepticus

Status epilepticus (SE) is defined as a condition in which a patient has a prolonged seizure or has recurrent seizures without fully recovering in the interval. With respect to the most severe seizure type (primary or generalized tonic-clonic) a duration of 5 min is sufficient for diagnosis of status epilepticus. SE may occur in a person with chronic epilepsy (the most frequent cause being noncompliance) or in a person with an acute systemic or brain disease (such as hypoglycemia or stroke)....

Research Applications

Human fMRI based on the endogenous contrast agent (deoxyhemoglobin) was first reported in 1991. In the ensuing 10 years the growth of fMRI-based research applications has been explosive. The easiest (and probably the most accurate) way to summarize the range of fMRI-based research applications is all of psychology and neuroscience''. In addition to widespread reports of results of fMRI-based research in general scientific and popular journals, there are two journals devoted exclusively to the...

Neuroanatomical Hypotheses

Evidence for the neuroanatomy of pathological laughter and crying comes from the following sources a limited number of autopsy reports studies of congeni-tally malformed infants case reports of patients with pathological laughter following neurological disease EEG activity and electrical stimulation of the cortex injection of a barbiturate to the right or left cortex, typically done in patients with epilepsy to determine the language-dominant hemisphere and studies of humor comprehension in...

Cluster Headache

This form of vascular headache has been known as histaminic cephalalgia, Horton's headache, migrai-nous neuralgia, sphenopalatine neuralgia, petrosal neuralgia, red migraine, Raeder's syndrome, Sluder's syndrome, erythromelalgia, and Bing's erythroproso-palgia. The defining characteristic of cluster headaches is their occurrence in cycles (clusters) that occur and disappear spontaneously. There are two forms of cluster headache episodic and chronic. The majority of patients with cluster...

Psychiatric Disorders

A number of psychiatric disorders have been linked with abnormalities in the function of the anterior cingulate cortex. Activity is elevated in this region in obsessive-compulsive disorder, tic disorder, and depression, and normalization of activity in this region occurs with behavioral and pharmacological treatment of these disorders in some cases. With severe forms of these disorders, such as with obsessive-compulsive disorder, cingulotomies have been shown to be effective in relieving the...

Disorders Of Alertness

Fatigue is a deficit in alertness, which is a normal response following physical or mental exertion and instructs the body to rest and repair. Fatigue is a symptom of many illnesses, which reflects in part the importance of rest in recuperation from illness. However, there are occasions, such as after resting, when fatigue is inappropriate and, when alertness is required, debilitating. If such unexplained fatigue is persistent and is accompanied by other symptoms (such as sleeping problems,...

Axonal Transport

Impulse conduction is not the sole function of the axon. Macromolecules essential to structure flow from the soma down the axon. Other substances, e.g., tired axon terminal membrane requiring degradation and recycling, move up. Rates of axonal transport of these commodities vary strikingly some, including newly synthesized protein for neuronal repair, move slowly, at 0.2-5 mm day, whereas others related to transmitter synthesis travel 100-400 mm day. Two modes of axonal transport are known...

Familial Hemiplegic Migraine

Familial hemiplegic migraine is a rare autosomal-dominant migraine syndrome in which patients experience recurrent visual and somatosensory auras and prolonged hemiparesis in the context of migraine attacks. It may be associated with dysphasia, drowsiness, confusion, coma, and, in some, cerebellar symptoms, tremor and epilepsy. To establish a diagnosis, the patient must have at least one first-degree relative with identical attacks. This

Functional and Psychiatric Disorders

Stress, anxiety, depression, and other mood disorders can be reactive to the patients' current situation or can predate the cancer diagnosis. In either case, mood and adjustment disorders negatively affect patients' ability to focus, concentrate, and organize activities, leading to complaints of forgetfulness and other cognitive problems. Cancer patients are just as likely as the general population to suffer from major psychiatric disorders, such as bipolar illness, major depression,...

Neuroanatomy

We look at a motor neuron as a part of the motor subsystem of the nervous system. From the number of axon terminals on its receptive surface (around 50,000, each signifying a synapse), we see that this large cell, final in the chain of communication from sensory periphery to muscles, has a vast range of inputs. This includes PNS primary afferents, spinal and brain stem connections, feedback and feedforward circuits from other motor neurons, self-directed inputs...

Basic Structure Of The Brain

The brain has undergone a long process of evolution, taking millions of years for it to take the shape and organization currently found in man. During this evolution, the brain has increased not only in size but also in its level of organization, sophistication, and Encyclopedia of the Human Brain Volume 1 Copyright 2002, Elsevier Science (USA). complexity. The increased size of the brain, however, is not necessarily an indication of increased intelligence. Larger animals, such as the elephant...

Functional Specialization of Synapses

The structural diversity of presynaptic components is great one finds club endings, large end bulbs, small end bulbs, spiral endings that wrap around the axon hillock and initial segment of the target neuron, fibers of passage merely brushing the dendrites as they pass by, claw-shaped endings that seem to seize the cell body of a neuron or grasp a dendritic spine, extended zones of apposition of an axon and a dendrite, as in the case of the cerebellar climbing fiber, where numerous synapses are...

Intracranial Venous Disease and Stroke

Within the brain, there are several large veins that drain into the venous sinuses. Sagittal sinus thrombosis is the most serious disorder of the intracranial venous pathways. This condition frequently leads to headache (80 ), swelling of the optic nerve (papilledema, 50 ), motor or sensory deficits (35 ), seizures (29 ), hemorrhage (50 ), and death (5-10 ). Contrast enhanced CT scanning allowed superior sagittal sinus thrombosis to be diagnosed by showing the empty delta'' sign. Now, MR is the...

Subarachnoid Hemorrhage

Most subarachnoid hemorrhages (SAHs) are caused by a ruptured berry aneurysm. The patient with SAH will describe the worst headache of my life.'' Other causes of SAH include arteriovascular malformations, bleeding disorders, and miscellaneous or cryptogenic causes. A berry aneurysm results from a congenital weakness in the arterial wall, usually occurring in the vessels of the circle of Willis and at these vessels' bifurcations. Frequently, patients are drowsy, may vomit, and have meningeal...

Migraine without Aura

The headache is characterized by episodes of head pain lasting 4-72 hr and having at least two of the following characteristics pulsatile quality, moderate to severe intensity, unilateral location, and worsening with physical activity. To fulfill the IHS criteria for migraine, headache must also have occurred on at least five occasions and have been accompanied Migraine with Aura Diagnostic Criteria A. At least two attacks fulfilling B B. At least three of the following characteristics 1. One...

Lineage and Development

In the human brain, ependymoglial cells are thought to be derived from the developing neuroepithelium along a caudal-to-rostral gradient. Radial glial cells are the first subtype of neuroglia to appear during human fetal brain development. They stain intensely with GFAP and nestin early in development but lose immunoreactivity with time. It is thought that epen-dymoglia arise from a radial progenitor in a pathway that can also give rise to astrocytes. The radial progenitors differentiate into...

Chronic Paroxysmal Hemicrania

Chronic paroxysmal hemicrania (CPH) is a rare disorder. It has the same characteristics as cluster headache, including similar associated symptoms. These episodes are briefer, more frequent, occur mostly in females, and responsive to indomethacin. The patient with CPH will characteristically complain of 10-20 brief, intense focal episodes of head pain, localized mostly in the temporal, ocular, frontal, and upper jaw area. The pain has the same quality as cluster headache pain, but of even...

Chronic Migraine

Under the term chronic migraine, or transformed migraine, we propose to include all cases of chronic daily headache with features of a both migraine and tension-type headache that do not meet criteria for new daily persistent headache or hemicrania continua. Table V proposes criteria for chronic migraine. The typical patient is a woman with a past history of episodic migraine who develops a daily or almost daily headache that is mild to moderate in severity, with superimposed typical migraine...

Clinical Evaluation and Management

Imaging studies such as cranial CT or MRI can assist in determining the presence of complications following an anoxic insult. These studies can differentiate between an ischemic infarct, intracerebral hemorrhage, and a mass lesion involving the cortex or the brain stem. A CT without contrast is helpful in suspected cases of cerebral hemorrhage. Within the first 72 hr of intracerebral hemorrhage onset, a cranial CT usually provides greater resolution than a MRI. In addition, CT and MRI are...

Parts Of The Cerebral Cortex

The absence of clear anatomical boundaries has encouraged the development of numerous approaches to the subdivision of the cerebral cortex. The most commonly used map is based on Korbinian Brod-mann's parcellation of the cerebral hemispheres into more than 50 areas, each characterized by a specific pattern of neuronal density and lamination (Fig. 1). These cytoarchitectonic areas can be divided into five major functional zones limbic, paralimbic, heteromodal association, unimodal association,...

Genetics And Evolution

As described, the anterior cingulate cortex has been implicated in a number of psychiatric disorders. Interestingly, all of these disorders show familial patterns of inheritance, increased risk among first degree relatives of affected patients, and increased concordance in identical vs fraternal twins. The heritability (see Glossary) has been estimated for schizophrenia (0.6), attention deficit hyperactivity disorder (0.79), obsessive-compulsive disorder (0.68), and major depression disorder...

Normal Physiology and Function

The morphology and branching patterns of microglial cells display heterogeneity between different brain regions. Microglia in gray matter tend to be ramified, with processes extending in all directions. Cells in the white matter are bipolar and often align their cyto-plasmic extensions in parallel, at right angles to nerve fiber bundles. Thus, the morphology of microglia adapts to the architecture of the brain region they populate, whereas their phenotype appears to be influenced by the...

Motor Representations

Areas of neocortex also represent muscles and movements. Long before it was technically possible to record the small changes in the electrical activity of neurons in neocortex, it was possible to generate and deliver an electrical current to the surface of neocortex and observe the effects. From quite early studies, it became apparent that the electrical stimulation of locations in the frontal lobe was especially effective in evoking movements of various parts of the body and that different...

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...

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....

Cavernous Malformations

Cavernous malformations (or cavernous angiomas) affect both sexes equally. Estimates of lesion prevalence vary between 0.02 and 0.9 depending on the criteria and methods utilized for definition. Patients typically present in the second to fourth decades of life. Familial forms, characterized by multiple lesions and an autosomal-dominant inheritance pattern, are well described and prevalent in the Hispanic population. The natural history of cavernous malformations is not well defined. Cavernous...

Comorbidity of Migraine

The term comorbidity refers to the greater than coincidental association of two conditions in the same individual. Migraine is comorbid with many disorders (Table I). This can alert clinicians to identify them. Comorbid illness impacts pharmacologic treatment of migraine headache. One drug may be useful for more than one disease (i.e., valproate and topiramate may be therapeutic for both migraine and epilepsy). On the other hand, some treatments may be contraindicated in certain comorbid...

Epidemiology And Comorbidity A Migraine Prevalence

Migraine is a highly prevalent condition affecting approximately 10 of the population. Migraine prevalence is age, gender, and race dependent. Women are more affected (lifetime prevalence, 12-17 ) than men (4-6 ). In the American Migraine Study, the 1-year prevalence of migraine increased with age among women and men, reaching the maximum at ages 35-45 and declining thereafter. Migraine prevalence decreases in older women but never decreases to prepubertal or even male prevalence. Migraine...

Acute Subdural Hematoma

Subdural hematoma can be due to either an acute or a chronic event. In acute subdural hematoma, a brief lucid interval occurs between the head trauma and the patient becoming comatose, although the patient is usually comatose from the time of trauma. The bleed may be unilateral or bilateral and is often accompanied by lacerations of the scalp and contusions to the brain and parenchyma. A CT scan will confirm the diagnosis in up to 90 of cases, although angiography may be necessary....

Sinus Headache

Sinus headache is an often cited complaint of many patients, although the acute headache due to actual sinusitis occurs less frequently than the rate quoted by the advertising media. Acute sinusitis presents with fever, pain triggered by pressure or direct percussion, and headache. Fever is the cardinal sign of this infective process. The pain associated with sinus diseases is a constant, dull ache. If the patient is suffering from acute sinusitis, the headache will typically increase in...

Techniques Used in Humans 1 Microstructure

In humans, methods for direct investigation of axon connectivity are restricted to noninvasive approaches. At the microlevel of individual axons, morphological techniques are limited to a small number of methods that can be applied in postmortem tissue or surgical biopsies. First, the classical Golgi stain can demonstrate aspects of axon structure, especially in young tissue, although the identity and full conformation of long axons are difficult to establish. Second, degeneration methods can...

Synaptic Organization Of The Nervous System

This subject lies at the heart of the organization of the human or any other nervous system. A synapse, by definition, includes presynaptic and postsynaptic membranes separated by a narrow cleft about 1220 nm across. As noted, EM demonstration of this cleft provided definitive proof of the anatomical tenet of the neuron doctrine nerve cells are separate. The cells that face each other across this cleft may be two neurons, a neuron and a skeletal or smooth muscle fiber, or a neuron and a gland...

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...

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...

Migraine with Aura

The migraine aura is a recurrent neurologic symptom that develops gradually (in more than 4 min) and persists for less than 1 hr. Headache, nausea, and or photophobia usually follow within 60 min after resolution of the aura but may not necessarily develop (acephalgic migraine). Visual aura is most frequently reported (99 ), followed by sensory (31 ), aphasic (18 ), and motor aura (6 ). The stereotypical visual aura is a serrated arc of scintillating, shining, crenelated shapes that begins near...

Training Requirements

Few states regulate the practice of NF, yet it is being used with clients with a wide range of medical and psychological conditions. Many both inside and outside the field express alarm about potential dangers to the public when practitioners with minimal or no training in neurology or neuropsychology, or even general medicine or psychology, are treating persons with ADHD, depression, brain injury, and other conditions. Sometimes this is without supervision from or collaboration with trained...

Post Lumbar Puncture Headache

If a patient complains of headache following a lumbar puncture, it is probably related to a loss of CSF secondary to leakage through a dural defect. The headache is often exacerbated in the upright position and relieved with recumbency. The pain has been described as a dull ache that may become throbbing. The headache onset starts within hours to days after the procedure and may persist for 2 to 3 weeks. The symptoms usually subside spontaneously. Prevention is the key and the use of smaller...

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...

Contrast in an Image

As with any imaging modality, the key variable in producing a meaningful image is contrast. The signal measured at one point in space or time must be higher or lower than the signal at another point, and the variation in signal intensity across the image should systematically follow some variable of interest. In the endeavor of brain mapping, the ultimate variable of interest is neural activity. In order to measure local brain activity with MRI, one must exploit a chain of indirect linkages...

Migraine

This is a common syndrome of recurrent headache that is most often seen in young adults who are otherwise healthy. Even though these headaches are sometimes referred to as vascular headaches, the pathophysiol-ogy may not primarily implicate vascular mechanisms. It has been noted that migraineurs have slightly more MRI hyperintensities than do age-matched control subjects, and it is possible that episodic intracerebral vasoconstriction participates in their development. Clinical mainfestations...

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...

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...