The Fine Structure Of The Neuron

Despite their enhanced capacity to communicate, neurons are cells, showing familiar membranous, filamentous, and granular formed components. Yet the amount, arrangement, and function of these are distinctive, and a new component, the synaptic vesicle, unique to neurons is present. A neuron has two major compartments the nucleus and the surrounding cytoplasm. Within each, based on assumptions as to function, lie two categories of formed components organelles, found in all cells and considered...

Future Directions for the Treatment of Organic Brain Disease

In terms of preventing or reversing neuronal injury, peptide growth factors are increasingly being investigated as therapeutic regiments. Although currently the most efficacious application of growth factors involves the peripheral nervous system, progress is being made with central nervous system injury during both growth factor application and the generation of neuronal progenitor cells. The mechanisms employed by trophic factors to achieve neuroprotection can be diverse and not well...

Role of Reflexes in Voluntary Movement

To what extent are reflexes used for generation of voluntary movements Studies of patients with degeneration of large-fiber afferents (peripheral neuropathy) have led to the conclusion that reflexes play only an indirect role in volitional action. Such patients lose their stretch reflexes, limb position sense, and their ability to detect limb motion, but they can still make voluntary movements. In normal individuals, an electromyograph (EMG) pattern composed of three discrete bursts of activity...

Glial Fibrillary Acidic Protein

GFAP is an intermediate filament protein expressed in astroglia. It was first isolated from multiple sclerosis brain, in which astrocytes are very reactive. Intermediate filaments constitute major components of the cytoskeleton of eukaryotic cells as 10-nm filaments. On the basis of differences in size and amino acid sequences, GFAP together with vimentin and desmin are classified as type III intermediate filament proteins. They are composed of three distinct regions an amino- terminal head...

Physiology and Anatomy

The majority of fibers carrying information from deep mechanoreceptors end in spinal reflex loops or motor control centers in brain stem and cerebellum. Only a minor portion joins the leminiscal pathway and reaches primary sensory cortex via the ventrolateral thalamus. Both patients who completely lost the ability to exploit somatosensory afferences for motor control had peripheral nerve diseaeses that blocked somatosensory input before it reached even the spinal cord. Of the two patients with...

Clinical Implications Of Central Noradrenergic Systems

Several agonists and antagonists of noradrenergic receptors are currently used in the pharmacopea to interact with different diseases related to NE in the peripheral nervous system. For example, inhalation of b2-adrenergic receptor-selective compounds has long been established as an effective therapy for asthma and other bronchospastic condition, and b-blockers are used in the treatment of angina pectoris and cardiac arrythmias. They are both used as a treatment for acute congestive heart...

Neurophysiological Testing

Neurophysiological tests of central nervous system functioning, such as electroencephalography and evoked potentials, are obtained to provide additional objective evidence of an organic basis for the clinical behavioral findings. These tests can be used to detect possible diseases other than the disorder attributable to exposure to neurotoxicants. Abnormalities are not always revealed by these tests, but, when present, they may lend further support to a diagnosis of toxic encephalopathy. The...

Cancer In The Central Nervous System

Primary brain tumors, metastatic brain tumors, and leptomeningeal metastases directly alter the functioning of the brain and hence the individual's mental and cognitive functioning. Primary brain tumors are increasing in prevalence, with more than 29,000 new cases diagnosed each year in the United States. In addition, between 20 and 40 of patients with non-central nervous system (CNS) solid tumors develop brain metastases. Cognitive impairments are related to lesion location, tumor growth...

Enteric Glia A Anatomy

Enteric glia are different from other glial cells in that they are not located in the CNS but rather are located in the gut as part of the enteric nervous system (ENS). As such they are obviously distinct from glial cells in the central and peripheral nervous systems, but they do share common features that justify their inclusion in the family of neuroglia. The enteric nervous system is functionally different from the peripheral nervous system in that it is capable of mediating reflex activity...

Schwann Cells A Anatomy

Schwann cells surround all axons in the peripheral nervous system either by forming channels that are contiguous with the axonal membrane or by wrapping myelin around the nerves. Peripheral nerves are composed of an outer epineurium, which is composed of blood vessels, connective tissue, and fibroblasts, a perineurium, which is composed of flattened cells surrounding the nerves, and the intrafascicular endo-neurium, which contains supportive cells and the ECM that surrounds bundles of nerve...

Ineffective Phagocytic Activation of Microglia during Wallerian Degeneration

The simplest model of nerve injury is axotomy of fiber tracts. Transection or crush of a fiber tract in the nervous system leads to breakdown of axoplasm within days, loss of axonal connectivity, and to cellular and molecular changes in the distal nerve segment referred to as Wallerian degeneration. In the peripheral nervous system (PNS) nerve fibers promptly regenerate from the proximal stump into the degenerating distal nerve segment, but no such regrowth occurs in the CNS. One of the...

Islet Neuropeptides A Gastrin Releasing Peptide GRP

GRP is the mammalian homolog of the amphibian peptide bombesin. Bombesin is a 14-amino acid peptide that was initially isolated from the skin of the frog Bombina bombina in 1971 by Anastasi and collaborators. Three different families of bombesin-like peptides exist in amphibians (bombesins, ranaten-sins, and phyllolitorins). These peptides are localized to myoepithelial poison glands that are under adrenergic control and therefore likely function in defence against predators. During the 1970s...

Growth Hormone

The levels of growth hormone (GH) secretion by the pituitary are increased by the hypothalamic growth hormone-releasing hormone as well as by noradrener-gic and dopaminergic stimulation, whereas the release of GH is inhibited by somatostatin. Several studies have reported blunted responses of GH to clonidine in depressed men and postmenopausal women, suggesting dysfunctional a2 adrenergic receptors in depression. Also, blunted responses of GH to imipramine that persist despite effective...

Community Recreationleisure

Community recreation and leisure activities can provide individuals with CP a source of enjoyment and a lifelong opportunity for general fitness and wellness. Specifically, community recreational opportunities provide an outlet to engage in physical activity in addition to promoting independence and self-sufficiency. As individuals with CP age, they experience the normal sequala of the aging process in addition to already existing impairments in movement. Weak muscles may exhibit a decrease in...

Frontotemporal Dementias

FTD includes both Pick's disease and non-Pick's frontotemporal dementia (also called frontal lobe dementia, FLD), motor neuron disease, and progressive subcortical gliosis. Although estimates of the prevalence of FTD remain somewhat controversial, some investigators think that these disorders have been underestimated and could account for 10-19 of all demented cases. The usual age of onset is between 45 and 65 years, with equal sex incidence. A family history of the illness is present in...

Neonatal Rat Model

Neonatally infected rats may have a wide range of physiologic and neurobehavioral disturbances. They are smaller than uninfected littermates, display a heightened taste preference for salt solutions, and have altered sleep-wake cycles. There is no apparent alteration of glucose, growth hormone, or insulin-like growth factor-1 or amount of food ingested thus, the cause of runting remains obscure. Behavioral disturbances are less dramatic in neonatally infected animals than in their...

Dementias

Dementias involve cognitive deterioration (e.g., memory decrements and deficits in attention and concentration) and confusion that progress as a function of age. The most common and most widely studied dementia is Alzheimer's disease (AD). This condition remains a focus of extensive contemporary research, and its etiology is far from clear. However, research has indicated several likely etiologic factors, including the abnormal deposition of amyloid plaques around neurons and neuron bundles...

Dementia Associated With Depression

Depression in older age has been given increasing clinical and research attention. Although the preva lence of depression (according to standard diagnostic criteria) is not higher for older than for younger adults, older persons with depressive symptoms have health care costs about 50 higher than those without depressive symptoms. These increased costs are not accounted for by mental health service utilization. Depression frequently coexists with neurological disorders among older adults (e.g.,...

Cns Effects Of Nonbrain Cancer

Certain types of cancers cause brain dysfunction indirectly, causing paraneoplastic brain disorders. It has been estimated that 10 of cancer patients develop such a syndrome. Most commonly associated with small cell lung cancer (SCLC), paraneoplastic brain disorders typically manifest as a diffuse ence-phalomyelitis, including limbic encephalitis, cerebelli-tis, brain stem encephalitis, myelitis, and sensory or autonomic ganglionitis. The cognitive deficits associated with these disorders are...

Pathological Characteristics

Aneurysms arise predominantly at the branch points of the major intracranial vessels and rarely occur outside of the cerebral circulation. To explain the observed paucity of extracranial saccular aneurysms, it has been postulated that the intracranial arteries are predisposed as a result of the thinness of their walls (aneurysms have an attenuated tunica media and an absence of an external elastic lamina) combined with minimal perivascular support. The pathogenesis of cerebral aneurysms is...

Characteristics And Epidemiology Of Dementia

Most diagnostic criteria for the dementia syndrome stipulate that two or more cognitive functions must be sufficiently impaired so as to interfere with social and or occupational functioning and that there must not be clouding of consciousness. Clouding of consciousness, particularly in the context of a sudden onset of confusion, disorientation, hallucinations, disturbance in attention, or marked behavior change, is typically indicative of delirium (also termed acute confusional state)....

Treatment And Clinical Management Of Dementia

Pharmacological treatment options for the dementias presently are limited, although numerous experimental treatments are being evaluated. The one well-validated approach to symptomatic treatment of AD is based upon the documented deficit in acetylcholine neurotransmitter levels, due to the loss of cholinergic projecting neurons within the nucleus basalis of Meynert. It has been shown that this deficit can be partially compensated for by interfering with the action of that enzyme...

Respiratory Disease and Stroke

Respiratory disturbances may cause stroke if the oxygen delivery to the brain is sufficiently impaired. For example, sleep apnea is associated with a tendency to stroke and silent stroke as well as vascular dementia. Occlusion of the airway leads to cessation of air movement (apnea), causing oxygen levels to fall (desaturation) and carbon dioxide levels to increase (hypercarbia). Oxygen desaturation may be so severe that cardiac rhythm disturbances occur. Hypercarbia stimulates respiratory...

Dementia Screening Tools

Because detection of age-related cognitive impairments and dementia plays a significant role in neu-ropsychological evaluation, a number of specific screening tools have been developed (Table VIII). Many of these measures are designed to quickly assess gross level of functioning in major cognitive domains and can be administered in a matter of minutes (see Blessed Dementia Scale, MMSE). The Mattis Dementia Rating Scale is a more comprehensive set of items designed to stage severity of...

Diagnosis A Clinical

Infants may present with such symptoms as a large head, irritability, delayed development, and vomiting. Older children and adults may describe headaches, nausea vomiting, or visual changes (diplopia, decreased acuity, or field cuts) as high-pressure symptoms. In normal pressure hydrocephalus the symptoms are gait difficulty, slowing of action, memory loss, and incontinence. a. Infants Before the cranial sutures are closed, the size of the head will enlarge in hydrocephalus. The fontanelles may...

Congenital

Several congenital structural abnormalities can lead to obstruction of CSF flow and result in hydrocephalus. Different conditions may obstruct the aqueduct, leading to CSF accumulation above the level of the aqueduct that may be congenitally stenosed, occluded by a septum, compressed by gliosis in the surrounding periaqueductal tissue, or forked. It can also be compressed or kinked by structural abnormalities or masses. In aqueductal stenosis, the fourth ventricle, which lies beyond the point...

Williams Syndrome

Approximately 1 in 20,000 live births results in a child with Williams syndrome (WS), and it is equally distributed across ethnic groups. WS is a multisystem disorder that includes impairments in cognition, congenital heart disease, dysmorphic facial features, and connective tissue problems that impact the bowel, bladder, skin, and joints. Individuals with WS also have distinctive personality characteristics. Diagnosis in infancy most often is a result of a triad of symptoms developmental...

Circadian Disorders

Disorders of the circadian timing system are more common than previously thought. Circadian dysfunction is thought to be a common contributing factor in both sleep-wake disorders and affective disorders. The etiological bases of most circadian disorders are not known. However, such problems are thought to result from either compromised pacemaker function or faulty signaling to effector systems, or from other factors. Circadian function disorders are often manifest in the elderly, the blind, and...

Conclusions

Neuroanatomical, neurofunctional, and neurobeha-vioral findings in autism all suggest that the disorder cannot be reduced to one primary deficit that underlies the disorder. Thus, there is not just one important neural defect or one important neurobehavioral deficit there are many. Such neurobehavioral domains include, but are not limited to, deficits in reciprocal social interactions, affective responses, verbal and nonverbal communication, face perception, problem solving, working memory,...

Behavioral Pharmacology Of Drug Abuse

Behavioral pharmacology is one of the fields (along with neuroscience, neurochemistry, sociology, psy chiatry, epidemiology, etc.) that are pursued in the hope of greater understanding of the phenomena of abuse of drugs. The present discussion will attempt to relate behavioral pharmacological matters to phenomena of drug abuse in society. It seems self-evident that in the abuse of drugs, such as intravenous injection of heroin or sniffing of cocaine base, the drug represents the reinforcer that...

Language and Speech Abnormalities 1 Characteristics

It is the delay or regression of language, usually at approximately age 2, that first prompts parents to seek professional help. Although such delays are significant indicators of problems in child development, they are not specific to autism and are commonly found in many other childhood disorders (e.g., general language delay). By itself, language delay does not account for most of the features of the disorder but can be used as a metric for predicting developmental outcome. For example,...

Diabetic Ketoacidosis

Diabetic ketoacidosis may be complicated by rapid neurologic deterioration with severe brain injury due to osmotic cerebral edema. Hyperglycemia produces serum hyperosmolarity with the generation of idio-genic osmoles within brain cells in an effort to prevent cell shrinkage. During the treatment of diabetic ketoacidosis, rehydration with hypotonic solution and administration of insulin result in dramatic fluctuations in osmotic gradients. The osmoprotective molecules within brain cells result...

Treatment Issues

When symptoms first start in children and adults, an extensive physical exam from a qualified physician is immediately required. Both depression and manic symptoms can stem from problems ranging from vitamin deficiencies or excess to major autoimmune, cardiovascular, gastrointestinal, endocrine, hematolo-gic, neurological, and pulmonary diseases or malignancies. Additionally, a long list of medications and drug interactions can cause manic-depressive behaviors. Commonly, bipolar symptoms caused...

Chemotherapy

Many cancer patients experience difficulties with short-term memory during cancer therapy. However, approximately 18 of cancer patients who have received standard-dose chemotherapy manifest persistent cognitive deficits after treatment is completed. The risk appears to be greater after high-dose chemotherapy with stem cell rescue on the order of one-third of patients. This risk is evident 2 years after treatment, but the longer term effects of high-dose therapy remain unknown. Although most...

Symptom Profile And Neural Bases A Social Abnormalities 1 Characteristics

When Leo Kanner was deciding on a name that might most aptly characterize his original 11 cases, he chose the term autism, derived from the Greek work autos or self. His choice likely emerged from the strong sense of a preference for isolation, or the self, to the company of others observed in all his cases. Indicators of social abnormalities are noted early in autism, quite often as early as the first few months of life. Parents often remark that as infants, their autistic children stiffened...

Suggested Reading

W., and DeYoe, E. A. (1997). Graded effects of spatial and featural attention on human area MT and associated motion processing areas. J. Neurophysiol. 77(7), 516-520. Breiter, H. C., Gollub, R. L., Weisskoff, R. M., Kennedy, D. N., Makris, N., Berke, J. D., Goodman, J. M., Kantor, H. L., Gastfriend, D. R., Riorden, J. P., Mathew, R. T., Rosen, B. R., and Hyman, S. E. (1997). Acute effects of cocaine on human brain activity and emotion. Neuron 19(9), 591-611. Brewer,...

Evidence for Bidirectionality

Despite the fact that research has only recently begun to focus on the sensory capabilities of the immune system, much evidence has been collected that supports the existence of bidirectional communication. First, the immune system and the CNS make use of the same messenger molecules. There is a commonality in their production of and sensitivity to hormones and neurotransmitters. For example, although traditionally research has examined the impact of stress on levels of cytokines, IL-1 has been...

Attention Deficit Hyperactivity Disorder

A role for altered dopamine neurotransmission as the underlying cause of ADHD has been suggested by several observations. First, drugs used to treat ADHD, such as methylphenidate (Ritalin) and amphetamine (Adderal), increase synaptic levels of dopamine in experimental animals and in human subjects. In patients with ADHD, the maximal therapeutic effects of these drugs occur during the absorption phase of the kinetic curve, which parallels the acute release of dopamine into the synaptic cleft....

Understanding Neurological and Psychiatric Disorders

In contrast to presurgical planning and some pharmacology, the application of fMRI-based studies to neurological and psychiatric disorders might better be characterized as occurring in the developmental rather than application stages. The primary thrust is in the area of refining diagnosis. The wealth of studies using neurologically intact subjects supplies a natural baseline for using fMRI to derive more sensitive and or more specific diagnostic criteria. For every robust finding in the...

Contributions from Neuroimaging Studies

For an overview of findings in imaging studies see Table III. Digital processing of magnetic resonance imaging (MRI) of the brain can quantify three-dimensional volumes of brain structures. Nonquantitive studies found evidence of abnormalities in temporal lobe in patients with PD, and one quantitative study found decreased volume in the hippocampus. A reduction in hippocampal volume has been reported in several studies in patients with PTSD (Fig. 1). This hippocampal volume reduction has been...

Psychoanalytic and Psychodynamic Theories

Sigmund Freud and his followers developed the first psychological theories of depression. According to Freud, depression (or melancholia) was comparable to normal grief following the loss of a loved one. Depression, however, would occur in certain people who experienced a loss or disappointment at an early age. These individuals would actually feel rage at the lost loved object, but since part of their personality had become identified with this lost loved object, the individuals would then...

Psychological Treatments For Depression

There currently exist many different psychological treatments with varying levels of empirical support for their efficacy in treating depression in adults and a few that have been evaluated with children and adolescents. Although each has been developed and studied in its pure form, most psychotherapy available in the community incorporates some elements from more than one theoretical orientation. Psychodynamic psychotherapies evolved from psychoanalytic therapies, and as such they were...

Brain Behavior Findings

There is inconclusive evidence from electrophysiological and PET blood flow studies suggesting that language deficits in autism may be associated with a lack or reversal of left hemisphere dominance found in most normal adults. However, abnormal asymmetries have been observed in other electroencephalogram, ERP, PET, and SPECT studies that did not involve language tasks. It therefore remains open whether there is any specific link between functional asymmetries and language impairment in autism.

Clinical Applications

The ability of fMRI to image brain activity in vivo makes it a promising tool for the diagnosis, interpretation, and treatment evaluation of clinical disorders involving brain function. A great deal of effort is currently being exerted to develop concrete clinical applications for fMRI as well as to use fMRI to better understand various psychiatric and neurological disorders. Until we better understand the wealth of data being generated from neurologically intact individuals, however, the use...

Use of Behavioral Responses

The use of behavioral responses in fMRI-based studies began as a comforting demonstration that subjects were doing what the experimenter had asked them to do. However, behavioral measures can be much more useful. Two studies of memory, for example, made use of behavioral data collected after the MRI scanning session was over and the subject was out of the magnet to retroactively specify the data analytic process. One study of the effects of a drug used the subject's behaviorally reported mental...

L Gastrointestinal Function Blood Glucose and Food Intake

Preganglionic axons of parasympathetic neurons in the dorsal motor nucleus of the vagus project via cranial nerve X to ganglia in the wall of the gastrointestinal tract (the enteric nervous system) and to other parasympathetic ganglia in the region of the different abdominal viscera. The vagal motoneurons play a very important role in regulating motility (e.g., stomach contractions) and secretory functions (e.g., gastric acid) of these organs. The central nervous system coordinates the function...

Outcome

The majority of studies addressing outcome in somatoform illness have concentrated either on conversion disorder or on somatization disorder, and research explicitly addressing other forms of somatoform illness is rare. It is nevertheless likely that studies investigating the outcome of conditions such as chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, and chronic pain conditions are implicitly addressing other aspects of somatoform illness. A review of the substantial...

Prevalence Of Anxiety Disorders

The American Psychiatric Association first recognized anxiety disorders in 1980 as a separate group of psychiatric disorders. The concept of neurosis (neurasthenic neurosis, anxiety neurosis, phobic neurosis, and obsessive-compulsive neurosis) in previous classifications was abandoned because it was considered too vague. Anxiety disorders now include PD, PTSD, social phobia, specific phobia, OCD, and GAD. Anxiety disorders are by far the most common of psychiatric disorders (25 ), followed by...

Intracranial Arterial Disease and Stroke

Intracranial arterial disease may lead to ischemic and hemorrhagic strokes. Aneurysms and arteriovenous malformations (AVMs), intracranial atherosclerosis, and vasculitis are some of the major diseases of intracranial arteries producing stroke. Approximately 80 of nontraumatic subarachnoid hemorrhage is due to ruptured intracranial aneurysm. Arteriovenous malformations carry a 40-50 lifetime risk of rupture with subsequent fatal or disabling hemorrhagic stroke. Central nervous system vasculitis...

Norepinephrine

Norepinephrine release in the brain represents an important part of the immediate stress response, reacting within seconds. The majority of noradrenergic cell bodies are located in the brain stem, in the LC, with axons that extend throughout the cerebral cortex and to multiple subcortical areas. Neurons in the LC are activated in association with fear and anxiety states and the limbic and cortical regions innervated by the LC are thought to be involved in the elaboration of adaptive responses...

Pharmacological

A wide range of pharmacological agents have been used as viable treatment options for autism, ranging from serotonin uptake inhibitors, such as clomipra-mine and even the common antidepressant Prozac, to dopamine antagonists such as haloperidol. Overall, drugs have not proven successful at ameliorating the key features of autism but, rather, may have a modest effect on specific features of the disorder for some children. For example, serotonin uptake inhibitors (known to be effective in the...

Associated Features 1 Mental Retardation

A robust finding is that approximately 75 of individuals with autism also meet DSM-IV criteria for mental retardation. For the minority with normal intellectual functioning, subtle deficits in social and language behavior clearly set them apart from their typically functioning peers. There is no consensus regarding the role of mental retardation in autism and scientists have approached the topic in several ways. One thought has been that since mental retardation is not specific to autism (e.g.,...

Alcoholic Deterioration

Progressive ataxia, degeneration of cerebellar Purkinje neurons, cerebral atrophy, and mild to severe dementia have been described by many authors as findings typically associated with chronic heavy alcohol use. In one study, loss of Purkinje neurons from the cerebellar vermis correlated with long-term daily ingestion of moderate doses of ethanol, but in other studies a definite correlation could not be established between either cerebrocortical or cerebellar atrophy and the long-term pattern...

Spatial Place Attribute

With respect to short-term or working memory, the data indicate that animals and humans with damage to the hippocampus are severely impaired in working memory for spatial information, including spatial features such as allocentric spatial distance, egocentric spatial distance, head direction, and spatial location. In contrast, rats, monkeys, or humans with damage to the hippocampus are not impaired in working memory for response, reward value (affect), or visual object attribute information....

Impairments And Management

Treatment of the individual with CP is focused on maximizing functional independence while preventing the occurrence of secondary conditions. Associated primary conditions include abnormalities of posture and movement as well as learning disabilities, seizures, and problems with vision, hearing, and speech. Over time, movement abnormalities often place abnormal stresses on joints, resulting in secondary conditions such as joint contractures and bony deformities. Treatment interventions may...

Dyslexia

A particularly active area of clinically relevant research using fMRI is the study of developmental dyslexia. What makes this effort especially promising is that reading is of such fundamental importance to society and education, but there is limited understanding of the development and actions of the relevant cognitive systems underlying reading, even in normal readers. Psychophysical studies of temporal processing, not only in the auditory domain but also in the context of motor activity and...

Wernickes Encephalopathy

Neuropathologists have recognized for many years that chronic heavy ethanol intake can result in a syndrome first described by Wernicke in 1881, in which neurodegenerative changes occur in the thalamus, periaqueductal region, and floor of the fourth ventricle. Individuals with Wernicke's encephalopathy typically manifest a triad of clinical symptoms consisting of ocular abnormalities, ataxia, and a disturbance in consciousness varying from mild confusion to a profound comatose state. Whether a...

Disorders Involving Educational Behavioral Intervention

It is noteworthy that the medical phenomena just described, as well as a wide range of other medical phenomena with neuropsychological substrates (e.g., HIV-AIDS, sickle cell anemia, hypoxic episodes, and degenerative disorders, genetic and metabolic disorders), may profit from educational modifications to accommodate neuropsychological anomalies associated with the disorder, as well behavioral intervention in the form of counseling for educators and parents concerning reasonable expectations...

Historical Overview

Perhaps the most influential early contributions to the understanding of dyslexia were provided in the 1890s by Dejerine, who described two patients with quite different patterns of reading impairment. Dejerine's first patient manifested impaired reading and writing subsequent to an infarction involving the left parietal lobe. Dejerine termed this disorder ''alexia with agraphia'' and attributed the disturbance to a disruption of the ''optical image of words'' that he thought to be supported by...

Cell Biology Of Insulin Secretion

The islet nerves and their neurotransmitters alter islet hormone secretion through surface-located receptors, which affect the cell biology of exocytosis of the islet hormones via signaling systems. Several transduction mechanisms are operative in b cells, transmitting signals for the stimulation or inhibition of insulin secretion. A primary mechanism underlying insulin secretion involves b cell metabolism of glucose, which increases the cytosolic ratio of ATP ADP. This depolarizes the plasma...

Phonological Dyslexia Reading without Printto Sound Correspondences

First described in 1979, phonologic dyslexia is perhaps the purest of the central dyslexias in that, at least by some accounts, the syndrome is attributable to a selective deficit in the procedure mediating the translation from print to sound. Thus, although in many respects less arresting than deep dyslexia, phonological dyslexia is of considerable theoretical interest. Phonologic dyslexia is a disorder in which reading of real words may be nearly intact or only mildly impaired. Patients with...

Reading Mechanisms And The Classification Of Dyslexias

Reading is a complicated process that involves many different procedures, including low-level visual processing, accessing meaning and phonology, and motor aspects of speech production. Figure 1 provides a graphic depiction of the relationship between these procedures. This ''information processing'' model will serve as the basis for the discussion of the mechanisms involved in reading and the specific forms of acquired dyslexia. It must be noted, however, that the dualroute model of reading...

Other Peripheral Dyslexias

Peripheral dyslexias may be observed in a variety of conditions involving visuoperceptual or attentional deficits. Patients with simultanagnosia, a disorder characterized by an inability to ''see'' more than one object in an array, are often able to read single words but are incapable of reading text. Other patients with simultanagnosia exhibit substantial problems in reading even single words. Patients with degenerative conditions involving the posterior cortical regions may also exhibit...

Copper Mediated Mutant SOD1 Neurotoxicity

As discussed previously, mutations in SOD1 cause up to 20 of cases of familial ALS, a fatal adult-onset motor neuron disease characterized by the selective loss of spinal and cortical motor neurons. A variety of in vivo and in vitro studies have demonstrated that the mutant enzyme causes selective neuronal degeneration through a gain of toxic property rather than a loss of SOD1 activity, consistent with FALS displaying an autosomal-dominant pattern ofinheritance. Although some FALS-linked SOD1...

Stroke Risk Factors

Stroke risk factors are very well understood. Both modifiable and nonmodifiable risk factors are important. The nonmodifiable stroke risk factors are age, ethnicity, and sex. There are several modifiable stroke risk factors, including hypertension, hypotension, diabetes, atrial fibrillation, congestive heart failure, coronary artery disease, smoking, hyperlipidemia, homocysteinemia, obesity, alcohol intake, and sedentary lifestyle. In addition, there are numerous predisposing factors, or stroke...

Miscellaneous Applications

As mentioned in an earlier section, it was a report of the successful use of a treatment protocol involving NF with a group of alcoholic clients that stimulated revival of interest in NF during the late 1980s. There continue to be reports of the successful use of that protocol and others involving NF with alcohol and drug addiction. However, to the author's knowledge, there have been no published reports of controlled research on this topic. As with NF treatment of dissociative disorders, most...

Mechanisms Of Stressrelated Immune Alterations

The finding that psychosocial stressors can evoke consistent changes in immune measures led researchers to begin searching for the mechanisms through which emotional states could impact immune levels. Results of these studies suggested that stress has both direct and indirect effects on immunity. Direct effects stem from the activation of the two primary stress pathways the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. SNS activation is accompanied by...

Traumatic Stress and Posttraumatic Stress Disorder

Although many studies have examined the effects of acute, laboratory stress and chronic, naturalistic stress on immunity, relatively few have studied immune alterations in response to severe, traumatic stressors. Stressors can vary along many dimensions, including the duration of the event, the duration of threat experienced, and the duration of responding to the stressor. Therefore, distinguishing between acute and chronic stressors may be too simplistic and may not encompass the full range of...

Laminar Differentiation

Neocortex varies in another way that also adds flexibility to its function. The laminar organization of neocortex has already been mentioned, as have the slight variations in the appearance and thickness of layers from cortical area to cortical area that reflect functional specialization. The same area can also vary across species in differentiation, so that the primary visual cortex in highly visual mammals, such as monkeys and humans, is more distinctively laminated than in poorly visual...

The Acting And Perceiving Hand

Many of our cultural and technological achievements that mark us as human depend on skilled use of the hand. We use of our hands to gesture and communicate, make and use tools, write, paint, play music, and make love. Thus, the human hand is a powerful tool through which the human brain interacts with the world. We use our hands both to perceive the world within our reach (haptic perception) and to act on this world. These two functions of the hand, which are largely accomplished by touching...

General Comments on Laterality

Even though language function has been placed in the left hemisphere historically, the right hemisphere has also been shown to be crucial for language function. One theory from 19th century science was that language dominance was connected with manual dominance since the majority of individuals were right-handed, the left side of the brain was known to control the right side of the body, and most cases of aphasia were documented with left hemisphere lesions. Right-handed individuals with...

Relationship Between Visual Object Agnosia And Word And Face Recognition

One of the interesting recent developments in our investigations of object agnosia concerns different forms of category specificity, but here the category refers to different forms of visual stimulus recognition, such as face and word recognition. The critical issue is whether agnosia can be restricted to object recognition or whether it is reflects a broader form of visual impairment. In an extensive review of the literature, Farah suggested that the latter is more correct and that because...

Two Meanings Of Anger

The term anger is used in two distinct ways, both in everyday discourse and in scientific writings. First, in a generic sense, anger refers to a family of closely related emotions, including annoyance, rage, hostility, contempt, envy, fury, frustration, and jealousy. Second, in a specific sense, anger refers to one emotion among others in the same general class, such as when anger is contrasted with annoyance or rage. It is necessary to distinguish between the generic and specific senses of...

Achromatic Versus Chromatic Contrast

Achromatic contrast detects spatial differences, which depend on the distribution of light energy in the retinal image. For daylight vision, it is mediated by the two longer wavelength-sensitive cones. It is well developed in the fovea, mediating our highest spatial resolution, and represented in relatively large areas of visual cortex. The foveal area of striate cortex is about 36 times larger than that of striate cortex serving peripheral vision. In the fovea, the responses of neighboring...

Motion And Pursuit Eye Movements

The human visual field has a very high acuity central region, the fovea, and visual acuity declines rapidly for more peripheral regions. To position objects near the center of the fovea, humans and monkeys have developed sophisticated brain circuitry that produces two different types of eye movements saccades and smooth pursuit. Saccadic eye movements are rapid, step-like changes in eye position, that are used to quickly look around a scene or to read. Saccades have latencies of about 200 msec,...

Visuospatial Functions

After the integrity of basic visual acuity is established, the spatial distribution of visual attention is evaluated. The presence of visual neglect is assessed through the use of tasks that require scanning across all quadrants of visual space. Assessment of left-right orientation involves directing patients to point to specific body parts, either on themselves or the examiner. Topographical orientation can be tested by instructing the patient to indicate well-known locales on a blank map....

E Gaba Affects Overall Excitability

GABA is synthesized in both projection neurons (e.g., neurons within the striatum that project to the substantia nigra and globus pallidus) and interneurons (e.g., the basket cells of the dentate gyrus). Projection neurons are thought to play a major role in initiating postsynaptic activity, whereas interneurons are thought to modulate postsynaptic activity. Interneur-ons within the hippocampus appear to also form large circuits that underlie the theta rhythms in the brain. These slow (4-9 Hz)...

Treating The Human Disease

Current treatments for many human autoimmune diseases are largely based on immunosuppression, usually by giving medications such as corticosteroids, cyclophosphamide, azathioprine, or cyclosporin A, which inactivate or kill all classes of lymphocytes. In many patients these medications are effective in the short term only their administration does not usually alter the natural history of the disease, and the toxicity of these drugs is considerable. This toxicity is related to nonselective...

Alterations in Neurochemical Stress Response Systems in Patients with Anxiety Disorders

Anxiety disorder patients have long-term alterations in neurochemical systems that are involved in mediating the stress response and are sensitive to chronic stress. The findings in PTSD and PD (most extensively studied of the anxiety disorders) are summarized in Table II. Specific alterations in cortisol and HPA axis function are associated with PTSD. An increase in neuronal CRF release is a possible explanation for the clinical findings that have been reported for this disorder, with...

Betweenmodality Plasticity

Whereas anecdotal evidence of better audition after early blindness or better vision after early deafness exists, the available data are quite mixed. The longheld belief that multisensory integration is a necessary step in optimal development led investigators to focus initially on the disabilities caused by early blindness or deafness. For example, a number of studies, mostly from the 1970s and the early 1980s, document deficient spatial abilities in the blind and deficient visual perception...

Natural Infections

Although infection may be asymptomatic, symptomatic disease typically follows a predictable course. Clinical signs at the onset of disease in horses and sheep are nonspecific excited or depressed behavior, hyper-thermia, anorexia, jaundice, constipation, and colic. Classical disease becomes apparent within 1 or 2 weeks. Animals maintain an upright, wide-based stance with their heads extended. Repetitive behaviors are common and may include vacuous chewing, circular ambulation, and running into...

Neuroendocrine Theories

Approximately 40-60 of depressed individuals produce and secrete excessive amounts ofcortisol, primarily during the afternoon and evening. In these patients, cortisol secretion returns to normal levels after the depressive episode remits. This excessive cortisol is thought to be due to the overproduction by the hypothalamus of corticotropin-releasing hormone (CTRH), a compound that is stimulated by norepi-nephrine and acetylcholine, leading some to believe that CTRH and the noradrenergic system...

Cerebral Achromatopsia

There are rare exceptions-to the tolerance of color discrimination despite large losses in acuity. An occasional subject loses color vision but maintains normal visual acuity after acquired damage of visual cortex. The cases that have been studied most completely with the entire gamut of color testing methods confirm major but not complete loss of color discrimination. They appear to be able to use wavelength contrast to detect objects but are unable to perceive colors from these cues. Such a...

Hypothalamic PituitaryAdrenal Axis

Cortisol has been recognized as a stress-response hormone because plasma levels are altered by environmental stress. Disturbances in the hypothalamic-pituitary-adrenal (HPA) axis due to mood disorders in humans were reported as early as 1943 by Pincus and Hoagland, who observed an elevation of urinary metabolites of adrenocortical secretion related to stress among test pilots. In response to anxiety or depression, an increase in norepinephrine (NE) activates the hypothalamus to release...

Ipy

Figure 4 Mid-dorsolateral and mid-ventrolateral frontal activation during musical tonal working memory tasks. The coordinates of peaks of activation from three PET studies of rCBF changes during tasks involving working memory for musical tones. All data are group averaged and transformed into a common proportional stereotaxic space (i.e., Taillarach and Tournoux). (Left) The coordinates are plotted onto one hemisphere of a surface reconstruction of a similarly transformed normal brain chosen at...

Cortical Signs Of Mental Workload

Cognitive psychologists have deliberated on the functional structure of mental workload for a number of years. Debate has focused on the two major issues of whether resources are unitary or fractionated into modules and given the latter, how the modules are defined. There is even argument concerning the notion of resources. Some investigators question the need for this construct, arguing that many aspects of complex human behavior, e.g., concurrent performance of two or more tasks, can be...

Physiology

Until the advent of the patch clamp technique in the early 1980s, Schwann cells were thought to be electrically passive. This advance in technology revealed the possible presence of voltage-gated ion channels on Schwann cells. It has since been shown that Schwann cells from a variety of preparations express a wide range of ion channels, including Na+ channels, K + channels, Cl channels, Ca2 + -dependent K+ channels, and Ca2+ channels. The role of these channels in Schwann cells remains unclear,...

Types Of Lesions A Vascular Lesions

Disturbances of cerebral blood flow are one of the most frequently encountered causes of neurological Etiology, Morphology, and Consequences of Vascular Malformations Brain stem aneurysms (1-2 of the population) Abnormal, focal or segmental extension of the brain stem arteries in cases of congenital weakness of the blood vessel walls at section with a high hemodyamic load, resulting in sack- or berry-shaped distensions of the walls, especially in ACA, and exit of ACP from ACI and ACM Birth...

Dendritic Spines

Certain dendrites possess fingerlike extensions, 1-2 mm in length, called dendritic spines. In low magnification images, a high density of dendritic spines gives dendrites a fuzzy appearance (Figs. 1 and 2). Spiny protrusions are also found on the cell soma and on the axon initial segment, but the dendritic spines are more numerous and have received the most study. Neurons that have large numbers of spines on their dendrites are referred to as spiny neurons, whereas those with smooth dendrites...

John C Mazziotta

Disorders of the human nervous system are among the most debilitating and devastating of all human illnesses. Such disorders not only affect the physical abilities of patients but often severely compromise the quality of life, the ability to function in society, family relations, and the ability to maintain gainful employment. As such, neurological, neurosurgical, and psychiatric disorders affect not only the patients but also their families and society at large because of the tremendous...

Neuronal Inclusions

Golden brown lipofuscin (lipochrome or fatty pigment) granules are found in neurons of the CNS. They are harmless byproducts of lysosomal activity, a wear-and-tear pigment increasing with aging. Lipo-fuscin may eventually displace the nucleus and organelles severely to one side of the cell body. Black melanin pigment is seen in certain clusters of specialized neurons. The substantia nigra of the midbrain and the locus ceruleus of the pons are the prime examples. The presence of lipofuscin seems...

Gaba And Disease

Defects in GABA synthesis, release, and response have serious consequences. Since GABA is a ubiquitous neurotransmitter, it can be argued that it has a role (direct or indirect) in most neurological diseases. The direct loss of GABAergic neurons in the striatum, for instance, is a hallmark of Huntington's disease. Parkinson's disease, however, results from a loss of dopamine neurons in the substantia nigra. The lost neurons normally project to GABA neurons in the striatum, and those lost...

Pupillary Light Reflex

The preceding connections permit a modern understanding of the pupillary light reflex. Light shone in one eye (e.g., the right eye) is conducted via the right optic nerve to both sides of the pretectum after crossing in the optic chiasm. The pretectal olivary nuclei on each side will then receive a neural signal related to the brightness of the light shone in one eye. This signal is relayed by each pretectal nucleus to both Edinger-Westphal nuclei. As a result there is a crossing at the chiasm...

Movement Disorders

Movement disorders involve abnormal, insufficient, or excessive motor activity. Most of the movement disorders involve stiffness, rigidity, bradykinesia (slow movements), tremors, tics, gait difficulties, and loss of control of movements. The most common movement disorder in neurology is Parkinson's disease, which is by far the most studied and well-understood. Other conditions include Tourette's syndrome, tremors, and myoclonus. Parkinson's disease is characterized by resting tremor (a tremor...

General Intellectual Ability

Determination of an individual's level of intellectual functioning is a fundamental component of the neuropsychological assessment. Once established, general level of intelligence serves as a point of reference from which to evaluate performance in other domains. Intelligence encompasses a broad range of capacities, many of which are not directly assessed in the traditional clinical setting. The estimate of general intellectual ability is based on both formal assessment methods and a survey of...

Emotional Affect versus Cognitive Processing Load

A unique strength of functional brain imaging is the ability to test various intuitions and hypotheses about our mental activities by virtue of the quantitative nature of the MR signal changes. Sometimes the most salient aspect of a stimulus (such as its emotional valence) may be less cognitively engaging than the lack of that cue. Specifically, although the localization of function repeatedly found in studies of the low-level aspects of sensory processing appears to have analogs in other...

Integrative Agnosia

Lissauer's dichotomy makes provision for two main stages of processing, apperception and association. Object recognition, however, involves more than matching stimuli coded in terms of primitive features such as line orientation to stored knowledge. Instead, the spatial relations between the lines and features need to be coded, the object needs to be segregated from its ground, and parts of an object need to be related and integrated. These processes are typically thought of as serving...

Cerebellum and Writing

Support for the hypothesis that the cerebellum is a cognitive controller outside the main cognitive processor but necessary for intermodule coordination derives from the observation that cerebellar patients can develop peripheral afferent dysgraphia. According to recent theories on the dysgraphias, peripheral afferent dysgraphia is characterized by two different groups of deficits. The first group, the so-called neglect-related features, is characterized by the tendency to write on the...

Mechanisms Operative in the Developing Brain

Many efforts during the past two decades to develop a suitable animal model for studying FAS met with only limited success. Microencephaly (reduced brain mass) is a characteristic finding in FAE FAS victims, and it was demonstrated that exposure of immature rodents to ethanol in late gestation or during the first two postnatal weeks caused a reduction in brain mass. However, numerous additional animal studies failed to provide an explanation for the reduced brain mass. A modest loss of neurons...

Islet Localization Of Neuropeptides

Immunocytochemistry has revealed three neuropeptides to presumably parasympathetic nerve terminals in pancreatic ganglia and in islets gastrin releasing peptide (GRP), vasoactive intestinal peptide (VIP), and pituitary adenylate cyclase activating polypeptide (PACAP). These neuropeptides are released from the pancreas upon electrical vagal activation and they stimulate both insulin and glucagon secretion, as demonstrated in a number of studies in vivo as well as in vitro. From both a...