Symptoms And Classification A The Nature of Communication Behavior

Broca Aphasia Pantommime

When an individual generates an idea that he or she wants to verbalize, certain physiologic and acoustic events must take place in order for it to be transformed into words and sentences. The message is converted into linguistic form at the listener's end. The listener, in turn, fits the auditory information into a sequence of words and sentences that are ultimately understood. The system of symbols that are strung together into sentences expressing our thoughts and the understanding of those...

Normal Anatomy of the Cerebral Arterial Vasculature

Middle Cerebral Artery Anatomy Angiogram

Although the brain accounts for just over 2 of the body's total weight, it receives nearly 20 of the cardiac output. Whereas larger cerebral vessels are influenced by a balance of sympathetic and parasympathetic tone, vascular tone in medium and small cerebral vessels is altered primarily by the mechanism of autoregulation. Blood flow is tightly regulated at the arterial level to maintain an average cerebral blood flow CBF of 50 ml 100 g min. Smooth muscle cells within the cerebral vessels...

Anatomical Distribution In The Central Nervous System

Metabolic Pathway For Dopamine

There are several dopamine-containing pathways in the CNS. The nigrostriatal dopamine pathway accounts for approximately 70 of the dopamine in the brain. Cells bodies in this pathway are located in the substantia nigra pars compacta and project to the caudate, putamen, and the globus pallidus Fig. 1 . An interesting characteristic of these dopamine neurons is that they contain extensive dendritic trees, which extend ventrally into the substantia nigra pars reticu-lata. Dopamine release occurs...

Brain Structures Involved In Human Classical Conditioning

Although studies of classical conditioning in humans began to wane in the 1960s, particularly for eyeblink classical conditioning, within the past 10 years there has been a resurgence of experimental work that can largely be attributed to the success of classical conditioning as a tool to study brain function in the experimental animal. Currently, our understanding of how different human brain structures contribute to classical condition lags far behind what is known in the animal and will...

Anatomical Brain Defects A Multiple Anatomical Abnormalities

Subcortical Structures Color

Among all types of biological abnormalities in autism, evidence for neuroanatomical abnormality is the strongest. Studies show that in autism, most major brain structures are affected Fig. 6 these include the cerebellum, cerebrum, limbic system, corpus callosum, basal ganglia, and brain stem. Recent evidence shows that within the cerebellum and cerebrum, there is abnormality in white and gray matter. Such widespread anatomic abnormality explains why autism involves pervasive and persistent...

Peripheral Agraphias

Where Angular Gyrus Axial

Clinically, the peripheral agraphias are characterized by defective selection or production of letters in handwriting. In pure cases, the central or linguistic components of writing are intact, and the preservation of orthographic knowledge can be demonstrated via spared output modalities that include oral spelling, typing, and spelling with anagram letters. The major subtypes of peripheral agraphia include allographic disorders, apraxic agraphia, nonapraxic disorders of motor execution, and...

Neuroanatomical Correlates of Declarative Memory

Amygdala Emotion Star Wars

Several brain regions are believed to be important to encoding and storage of long-term declarative memories. These include structures in the medial temporal lobes, medial diencephalon, basal forebrain, and prefrontal cortex. In addition, certain subcortical nuclei and white matter pathways are important for retrieving acquired information from storage. The gross anatomy of the lateral and medial surfaces of the brain is illustrated in Figs. 6 and 7, whereas some of the more important...

A A Biological Clock in Hypothalamus

It has long been clear that mammals and other organisms exhibit daily cycles in physiology and behavior that persist in the absence of sensory input from the environment. These cycles are approximately 1 day in length hence the term circadian and in normal circumstances are synchronized with the environment. In essence, they are rhythms of behavior and physiology that are tightly coupled to the most pervasive signal in our environment, the daily rhythm of light and dark. The adaptive...

Dopamine And Neuropsychiatric Disorders

Many lines of evidence suggest a role for dopamine in neuropsychiatric disorders such as PD, schizophrenia, attention deficit hyperactivity disorder (ADHD), and drug abuse. The first evidence for dopamine's involvement in these disorders came from either postmortem histological neurochemical studies or the observation that the drugs used to treat these disorders either increased or blocked dopamine neurotransmission in the brain. Since the advent of neuroimaging techniques such as positron...

The Physiology Of Nausea And Vomiting

Emesis Mechanism

Nausea is a highly subjective and peculiarly unpleasant sensation, quite distinct from other feelings. It is felt Encyclopedia of the Human Brain Volume 3 Copyright 2002, Elsevier Science (USA). in the throat or stomach or as a sinking sensation in the epigastrium the symptoms may include malaise, drowsiness, anxiety, and reduced vigilance. It is invariably accompanied by autonomic changes including vasomotor disturbances, causing vasocon-striction-pallor and pupil dilation, tachycardia,...

Anatomic Subdivision Of Cerebellum

Cerebellum Lobes Roman Numerals

When the occipital bone is opened, the dorsal surface of the cerebellum is clearly visible in the posterior cerebral fossa. The most prominent aspect of the cerebellar surface is the presence of many parallel convolutions that run perpendicular to its anteroposterior axis. In saggital sections, this chain of parallel convolutions has a characteristic appearance, like leaves stemming from the same trunk. This feature, defined by early anatomists as arbor vitae ''life tree'' , is at the origin of...

The Limbic System And Psychiatric Disorders

Although lesions of limbic structures do not result in apparent sensory or motor deficits, dysfunction of these structures has been associated with a variety of psychiatric disorders, including depression, bipolar disorder, obsessive-complusive disorder, and schizophrenia. For example, structural changes have been noted in the hippocampal formation, medial thalamus, and prefrontal cortex in schizophrenic subjects. Observations from positron emission tomography indicate that the amygdala and...

Psychogenic Nausea and Retching or Vomiting

A raised level of anxiety predisposes one to nausea and emesis 1. Chronic psychogenic vomiting'' (or usually retching) usually occurs upon getting up or just after breakfast it may persist for years. 2. Nervous dyspepsia'' is used to describe symptoms of a feeling of satiety, abdominal discomfort, nausea, and vomiting associated with psycho-neurotic features such as anxiety, irritability, and loss of weight. 3. Anorexia nervosa and bulimia have a well-established psychopathology in which...

Working Model For The Neural Circuitry Of Anxiety Disorders

Neural Circuits Anxiety Disorders

Anxiety disorders are characterized by dysfunction of an interrelated neurochemical and neuroanatomical system. PTSD and PD share many biological and phenomenological similarities that allow them to be considered related. Phobic disorders and GAD are still in early stages of investigation. Although phenomen-ologically they are similar to PTSD and PD, it is premature to include them in a model for human anxiety disorders. PTSD is related more to the deleterious effects of environmental stress,...

The Foveation System

Smooth Pursuit System And The Brain

As in most primates, the human retina has a tremendously specialized central zone, the fovea, where visual acuity is 1000 times better than vision just 10 eccentric. Hence, to look at'' something is effectively to foveate it. However, the fovea subtends only 1 of visual angle equivalent to the full moon's subtend . Therefore, the second principal function of eye movements is to foveate important parts of the visual scene. Foveation is accomplished by a triad of voluntary eye movements saccades,...

Nature And Nurture In Aggressive Behavior

Attempts to understand the brain basis of human aggression have often been thwarted by the outmoded dichotomies of nature versus nurture. Cultural and social influences are of critical importance in the genesis of human aggressive behavior. Violence may be motivated by the highest political and religious ideals and promoted and reinforced by cultural and governmental authorities. However, every violent behavior, whether springing from the most elevated or the basest of impulses, requires a...

Neuroplasticity in the Aging Brain

Neurotransmitter levels and mechanisms in the aged brain appear to vary from those in young and adult brains in many ways. Implants of young tissue into aged hosts, and those of aged tissue into young hosts, have been studied in order to determine the relative importance of intrinsic versus extrinsic influences in such factors as age-related adrenergic defecits. Receptor plasticity, the up- or downregulation of receptors for specific neuroactive substances, is an important mechanism of...

Anomia In Normal Aging

Whereas there are clear-cut naming problems associated with old age, the term anomia may be even less appropriate to describe them than the naming problems of Alzheimer's disease, perhaps because they are so much more subtle than the naming problems of aphasia. Indeed the term dysnomia here referring to a transient naming problem rather than a permanent disorder may more accurately portray the naming problems of aging in that it implies a more fleeting problem rather than an enduring...

Classification and Etiology

Putaminal Ich

No accepted classification schema exists for SICH. A long list of cerebrovascular disorders are associated with SICH. Hypertensive hemorrhages account for the majority. Other common causes include cerebral amyloid angiopathy, rupture of arteriovenous malformations and aneurysms, postischemic hemorrhage, tumors, and anticoagulation. However, significant overlap exists between these conditions. The etiology varies with age. Children to middle-aged adults present most commonly with lobar...