V Types Of Classical Conditioning
Classical conditioning is a generic term that can refer to a variety of different types of classical conditioning procedures and paradigms. Two different parameters can distinguish the type of classical conditioning i the temporal arrangement and spacing of the CS and the US and ii the type of response that is measured and conditioned. Some general comments regarding the influence that different types of conditioning have on behavior can be made, but it is impossible to make any specific...
Info Sqi
Fig. 1b . This phenomenon is called anodal break excitation or rebound spiking. The value of threshold depends on the duration of the stimulus Fig. 1c brief stimuli are required to be larger to evoke an action potential. Threshold also depends on more subtle features of the stimulus, such as its speed of onset. For a short time after an action potential has occurred, it is impossible to evoke a second one Fig. 1d . This period is referred to as the absolute refractory period ARP . After the...
A General Features
The pons metencephalon or ''behind-brain'' and medulla oblongata myelencephalon or ''medulla-brain'' are the two most caudal divisions of the brain, lying between the mesencephalon and the spinal cord. Seen from the ventral surface Fig. 1A , the boundaries between mesencephalon and pons pontomesencepha-lic sulcus and between pons and medulla oblongata pontomedullary sulcus are clearly demarcated by the massive population of transversely oriented pontocerebellar fibers. In contrast, there is a...
B Astrocytes Derived from SVZ Precursors
In the mammalian cortex, both neurons and glia arise from the proliferating neuroepithelial cells of the telencephalic ventricular and subventricular zone. The SVZ is a mosaic of multipotential and lineage-restricted precursors in which environmental cues influence both fate choice and all surviving cells. In the adult brain, SVZ astrocytes could be neural stem cells. The generation of astrocytes directly from SVZ cells was suggested by morphological observations Figure 2 Morphogenetic...
IV PERSISTENT VEGETATIVE STATE A Historical Background
The term vegetative refers to a passive or involuntary existence with limited cerebral activity. In 1972, Jennet and Plum described the vegetative state as a chronic condition following diffuse brain injury that resulted in the absence of cognitive function but the persistence of sleep-wake cycles. Individuals could open their eyes to auditory stimuli and were auto-nomically stable with the maintenance of respiratory and hemodynamic function. The American Neurological Association Committee on...
B Mental Flexibility
Mental flexibility requires the capacity to shift a course of thought or action according to rapidly changing situational demands. The Wisconsin Card Sorting Test WCST is a popular neuropsychological measure used to assess concept formation, abstract reasoning, and the ability to shift cognitive strategies in response to changing environmental contingencies. The subject is presented with four stimulus cards depicting figures of varying forms, colors, and numbers of figures one red triangle, two...
Flair
Figure 5 Hyperintense vessel on FLAIR and MRA in acute stroke. The occluded middle cerebral artery is seen on MRA arrow head, top left 6 hr following stroke. Hyperintense vessels are noted on FLAIR imaging arrow, bottom left . The T2 and T1 noncontrast images are normal adapted with permission from R. Bakshi and L. Ketonen, Brain MRI in clinical neurology. In Baker's Clinical Neurology R. J. Joynt and R. C. Griggs, Eds. . Copyright Lippincott, Williams amp Wilkins, 2001 . techniques have been...
A Sleep EEG Phenomena
In the neurophysiology of sleep two classic EEG phenomena have been established the spindles or waves between 7 and 14 Hz, also called sleep or sigma spindles, which appear at sleep onset, and the delta waves 1-4 Hz , which are paradigmatic of deeper stages of sleep. Recently, the work of Mircea Steriade and coworkers in Quebec described in animals another very slow oscillation 0.6-1 Hz that is able to modulate the occurrence of different typical EEG sleep events, such as delta waves, sleep...
Rrp 1
Figures The Hodgkin-Huxley model accounts for axonal excitability. a From top to bottom, applied current Iapp, membrane potential Vm, and each of the gating variables are plotted vs time. Curves were derived from the Hodgkin-Huxley model at 6 C. The rapid activation of the m gate underlies the action potential in response to this brief current pulse. The slower inactivation of the h gate and activation of the n gate repolarize the membrane a few milliseconds later. The duration of the absolute...
B Social Support
As mentioned earlier, research examining the relationship between quality of personal relationships and immune function has demonstrated consistent immu-nosuppressive effects in individuals who reported low marital satisfaction or who recently lost a spouse. Similarly, social support has been linked with physiological processes associated with risk for cardiovascular disease and cancer, and less social integration is associated with higher mortality rates from all causes. Individuals with high...
Cluster Headache Variant
These headache attacks are believed to be a form of cluster headache or CPH but do not meet their criteria. Cluster headache variant, originally described by Diamond and Medina, is a syndrome consisting of a triad of symptoms atypical cluster headaches, multiple jabs, and background continuous headache. The atypical cluster headache is irregular in location, duration, and frequency, occurring several times a day. Multiple jabs are sharp, variable, painful episodes, lasting only a few seconds...
B Somatization
Dissociation and conversion represent the main theoretical precursors to contemporary accounts of the somatoform disorders based on the concept of soma-tization. The term somatization originated in the psychoanalytic literature of the early 19th century as a label for the hypothetical process whereby bodily dysfunction i.e., unexplained symptoms was generated by unconscious neurosis.'' Since the 1960s, however, the work of Zbigniew Lipowski has encouraged many within the field to adopt a more...
IV ANATOMICAL BRAIN DEFECTS A Multiple Anatomical Abnormalities
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...
B Eeg
The interictal surface EEG is still the most important method in the diagnosis and assessment of all types of epilepsy. A routine EEG is recorded over 30 min during a relaxed condition, including photic stimulation procedures and 5 min of hyperventilation. Paroxysmal discharges strongly suggestive of epilepsy are spikes, spike waves, and sharp waves. These epileptiform patterns, however, are not specific for epilepsy. They may be observed in patients suffering from nonepileptic neurological...
Ii The Astrocyte Family
Astrocytes are a family of cell types that share certain morphological and functional similarities as well as biochemical and immunological features. Astrocytes are star-shaped cells, the processes of which occupy 25 of the volume of the CNS and extend into the surrounding neuropil network of intermingled and interconnected processes of neurons . They have an electron-lucent cytoplasm and several distinguishable morphological characteristics. First, as shown by electron microscopy, they contain...
Iii The Localization Of Function
To what degree can a complex psychological phenomenon such as anger be localized in the brain The answer to this question depends in part on the level of organization under consideration. The more elementary the response e.g., a reflex-like reaction , the more feasible its localization. At higher levels of organization e.g., an instrumental goal-directed act , the nature of the response depends less on a specific neural structure than on the interaction among different parts of the brain and on...
A The Ontogenetic View
From an ontogenetic point of view, tracing the growth of cognition in the individual organism, cognitive development has recapitulated the debate between nativism and empiricism that has dominated cognitive psychology at large. From the empiricist perspective, the child is a tabula rasa who acquires knowledge and skills with learning and experience. From the nativist perspective, even neonates possess at least primitive cognitive faculties, which develop further from interaction with the...
Computerized Tomography
CT is obtained urgently to exclude intracerebral hemorrhage and to identify whether imaging evidence of acute infarction exceeds one-third of the middle cerebral artery territory. In the presence of hemorrhage or large stroke, thrombolytic therapy is contra-indicated. A hyperdense MCA sign'' Fig. 2 may indicate thrombus within the middle cerebral artery and correlates with a worse outcome. Early changes of stroke may not be evident on CT for several hours after the stroke. Sudden deterioration...
B The Foveation System
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,...
E Neural Circuitry of Smooth Pursuit
1. Tracking with Pursuit and Saccades Smooth-pursuit eye movements support scrutiny of objects moving in space by matching eye velocity to target velocity in order to both reduce retinal blur of the moving object and facilitate its continued foveation. Smooth pursuit occurs when the FS selects a moving target or when a previously selected stationary target starts to move. However, target selection for pursuit also activates the saccadic system hence, moving targets are usually tracked with a...
Glossopharyngeal Nerve
Like the vagus nerve, cranial nerve IX has five components, three of which are sensory and two of which are motor. The GSA component is a minor one, which innervates a small region of skin behind the ear. The GSA fibers of the glossopharyngeal nerve have cell bodies located in the superior jugular ganglion of IX, and they traverse the spinal tract of V to terminate in the spinal nucleus of V with similar GSA afferents from cranial nerves X, VII, and V. The GVA component of IX has a much more...
B Spatial and Temporal Resolution in HighSpeed MRI
The physiology of the circulatory system and the physics of the MRI devices constrain the spatial and temporal resolution of fMRI. Today, it is routine to obtain 1 x 1 x 1-mm structural MR images and 5 x 5 x 5-mm functional MR images. The temporal resolution of fMRI is on the order of 1-3 sec. Neither the spatial nor the temporal resolution numbers are indicative of absolute limits in terms of the physiology or the imaging hardware. Rather, they represent a snapshot in the development of...
C Connectivity
Investigations in nonhuman primates have shown the anterior cingulate cortex to be connected with a diverse range of cortical and subcortical areas. This brain region receives afferents from more thalamic nuclei than any other cortical region and also receives diffuse monoaminergic innervation of serotonin 5-HT , do-pamine, and norepinephrine from the raphe nucleus, locus ceruleus, and ventral tegmental area, respectively. The overall pattern of connectivity reveals a broad distinction between...
D Processing of Opioid Peptide Precursors
All these opioid peptides are generated by processing longer precursor proteins, which have been subsequently cloned. There are three distinct genes responsible for generating these peptides Fig. 2 . The pre-proenkephalin gene contains four copies of Met-enkephalin and one copy each of Leu-enkephalin, the heptapeptide Met-enkephalin-Arg-Phe, and the octapeptide Met-Enkephalin-Arg-Gly-Leu Fig. 2A . No dynorphin sequences are present within this precursor. However, the sequence of the gene...
EFunctional Imaging
Single photon emission computed tomography SPECT in epilepsy has mainly been confined to the Figure 3 Imaging findings in temporal lobe epilepsy with hippocampal sclerosis. Left MRI coronal top and horizontal bottom , inversion recovery sequence. Hippocampal sclerosis arrow . Right Interictal HMPAO SPECT shows extensive ipsilat-eral hypoperfusion. imaging of cerebral blood flow in focal epilepsy. The tracer most widely used is 99Tc-HMPAO. Interictally, there is localized hypoperfusion in an...
III TOPOGRAPHY A Sulci Fissures and Lobes
In addition to the cytoarchitectonic method of creating divisions, the extensive folding of the cerebral cortex also provides a means of identifying distinct regions in the cerebral cortex Fig. 3 . It is this extensive folding that greatly increases the surface area and thus the volume of the cerebral cortex. Although the folds delineate some of the functional areas of the cortex, the borders between the cytoarchitectonic divisions and the major and minor folds do not necessarily correspond....
D Clinical Evaluation and Management Vqz
Cranial imaging studies, such as CT or MRI, can assist in determining the etiology of the persistent vegetative state. Approximately 48 hr following a prolonged anoxic episode, hypodensities in the cerebral and cerebellar cortices and in the caudate and lenticular nuclei can occur. Days to weeks later, focal infarcts, edema, and atrophy may be evident. PET and SPECT provide an alternative method of imaging that assesses cerebral function rather than brain anatomy. In vegetative patients,...
B Acetylcholine
Acetylcholine is metabolized from choline and acetyl coenzyme A by choline acetyltransferase. Choline is available in food such as egg yolks, or by breakdown of phosphatidylcholine, more commonly known as lecithin, which is used as an emulsifier in foods such as chocolate. Choline is the rate-limiting step in the production of acetylcholine, such that insufficiency of choline in the diet can lead to deficits in acetylcholine, whereas dietary supplements can increase the production of...
D Mammalian Circadian Rhythms and the Endogenous Pacemaker
At the turn of the century, any observed oscillation in mammalian physiology or behavior was dismissed as a random fluctuation of little importance. This is largely because physiologists and physicians were grounded in the developing tenet of homeostasis. Homeostasis, a term coined by Dr. Walter B. Cannon, describes the relative constancy of the internal environment or milieu de interior. Although the concept of home-ostasis accounted for the presence of daily variations in physiological...
H Hematologic Disorders and Stroke
Disorders of the blood and blood products are a relatively common cause of stroke. Many hereditary conditions lead to a predisposition to the development of thrombosis, including Leiden factor V mutation, protein C deficiency, protein S deficiency, and antith-rombin III deficiency. Anticardiolipin antibodies and antiphospholipid antibodies may increase stroke risk as well. Sickle cell disease, SC disease, and polycythe-mia rubra vera also predispose to coagulation and stroke. An overabundance...
Jeffrey L Saver
University of California, Los Angeles I. Nature and Nurture in Aggressive Behavior II. An Integrative Neuroscience Approach to Aggression V. Brain Stem Regulation of Aggression VI. Hypothalamic Regulation of Aggression VII. Amygdala and Temporolimbic Cortex Regulation of Aggression VIII. Prefrontal Cortical Regulation of Aggression IX. Combined Lesions of Temporal and Frontal Lobes X. Hemispheric Asymmetries in the Regulation of Aggression XI. Neurochemistry of Aggression XII. Major Clinical...
Glossary Tsj
circadian rhythm A term coined by Franz Halberg in 1959 to describe the approximately 24-hr biological cycles that are endo-genously generated by an organism Latin circa about, dies day . entrainment When an exogenous stimulus achieves both phase and period control of one or more circadian oscillators, entrainment has occurred. free-running rhythms Rhythms that persist even when an animal is isolated from external time cues. These rhythms do not damp out, are self-sustained, and have a period...
Iv Transmission Of Sound Information By The Auditory Nerve
The term code as applied to the auditory system is simply a way in which information about a sound is represented in impulse activity of neurons. As in other regions of the central and peripheral nervous systems, the auditory system exhibits a variety of neural activities and, hence, a variety of candidate coding mechanisms. These include labeled lines place , firing frequency rate , temporal patterning, and ensemble firing. Each auditory nerve encodes the frequency, intensity, and temporal...
C Molecular Basis of Pacemaker Cell Coupling
It is not understood how the activity of autonomous pacemaker cells of the SCN is synchronized to form a unified endogenous oscillator. Unfortunately, empirically distinguishing between endogenous pacemaker components and synchronizing mechanisms is very difficult. Extracellular ion fluxes, small membrane-diffusible molecules, glial regulation, and neural adhesion molecules have been examined as possible synchronizers of SCN neurons. Synaptic transmission and calcium-dependent neurotransmitter...
Info Uvw
Figure 8 Auditory nerve discharges appear in synchrony with the stimulus waveform, such that when the nerve discharges it does so when the waveform reaches a peak from Yost, 2000 . Figure 8 Auditory nerve discharges appear in synchrony with the stimulus waveform, such that when the nerve discharges it does so when the waveform reaches a peak from Yost, 2000 . complex sounds and to the binaural cues of interaural time and level. It is possible that neural maps of auditory space might exist at...
G Korsakoff Syndrome
In 1887, Korsakoff described a clinical syndrome associated with chronic ethanol intake featuring amnesia, confabulation, disorientation in time and place, and peripheral neuropathy. The tendency of chronic alcoholics to suffer from nutritional deficiency and to display a mixed clinical picture, including symptoms of both the Wernicke and Korsakoff type, has led some investigators to categorize the two syndromes together under the heading Wernicke-Korsakoff syndrome and to ascribe the overall...
A EEG Arousal Is Controlled by Interconnections between the NMTs Thalamus and
Changes in the EEG during arousal are produced by an interaction of the NMTs with the cortex and thalamus. The NMTs control the strength and pattern of the coupling between the thalamus and the cortex. During rest or sleep, thalamic reticular neurons Fig. 1 emit rhythmic bursts of action potentials within a narrow range of frequencies 4-8 Hz . The bursting pattern is maintained as long as these cells are slightly Figure 1 A Early model of arousal systems, circa 1972. The RF was considered a...
I The Expression Of Fear And Anxiety
Emotion is composed of several elements, including affective valence and arousal. Fear, like anger, is a protective emotion. It is a feeling of agitation and anxiety caused by the presence or imminence of danger and refers to a state or condition marked by this feeling. Fear has evolved as a vitally important physiological response to dangerous situations that prepares one to evade or confront a threat in the environment. Fear has played a critical role in survival, and therefore efficient fear...
Vi Eventrelated Phenomena Eeg Desynchronization And Synchronization
The electrical activity of the brain is ever changing, depending on both exogenous and endogenous factors. The spatiotemporal patterns of EEG MEG activity reflect changes in brain functional states. These patterns are apparent as a sequence of maps of scalp activity that change at relatively short time intervals, on the order of seconds or even fractions of seconds. Dietrich Lehmann identified these series of maps as reflecting brain microstates and proposed that different modes of mentation...
C Animal Research in Fear and Anxiety
Animal tests of fear and anxiety are used both to screen new compounds for potential anxiolytic action and to study their neural substrates. Until the mid-1970s, animal tests consisted of delivering shocks as a punishment, most often for an operant lever-press response. These tests were developed as screening tests for the pharmaceutical industry. Matching particular tests of fear and anxiety to particular anxiety disorders is an extremely difficult task. The social interaction test placing...
I The Interpreter
The answer appears to be that we have a specialized left hemisphere system that my colleagues and I call the interpreter. This interpreter is a device or system or mechanism that seeks explanations for why events occur. The advantage of having such a system is obvious. By going beyond simply observing contiguous events to asking why they happened, a brain can cope with such events more effectively should they happen again. We revealed the interpreter in an experiment using a simultaneous...
Vi Higher Order Apperceptive Deficits
Many patients have been identified who, although still classified as having apperceptive agnosia, appear to have some residual visual processing ability and can copy and match objects to some degree. These patients have object recognition difficulty under challenging conditions and do somewhat better in more optimal conditions. For example, they are impaired at recognizing objects under poor lighting conditions when shadows are cast, creating misleading contours. An additional manipulation that...
B Neuropsychology of ObjectBased Attention 1 ObjectCentered Neglect
As with most neuropsychological studies of spatial attention, investigations of object-based selection have focused on patients with neglect following damage to the parietal lobe areas. Two key findings from neglect patients have implications for the neural basis of object selection. The first finding is that some of these patients exhibit object-centered neglect. The second finding is a hemispheric difference between object and spatial attention in patients with neglect. Some patients with...
Iv The Rostral Diencephalon
As outlined previously, we use the term rostral diencephalon to refer to the extratelencephalic part of the secondary prosencephalon. We hypothesize that it is divided in basal and alar plates across three prosomeres p4-p6 , with its alar plate forming the prethalamus and its basal floor plates representing the hypothalamus, as originally defined for human embryos by His in 1890 Figs. 2 and 4 . Although the diencephalic prosomeres p1-p3 represent the part of the extratelencephalic forebrain...
A Prism Adaptation
In normal subjects, flexibility of transformation from retinotopic to body-centered coordinates has been demonstrated by prism adaptation. When subjects view objects through laterally shifting prisms and try to reach for them, their hands will move toward the shifted location and miss the actual object. Subjects will see their hand deviating from the object's apparent location even further to the side of prism shift. After some trials, however, the direction of movement will adapt to the visual...
Ii Anosagnosia And Paramnesia
Neurology yields weird examples of how the interpreter can work, and understanding the interpreter increases our insight into some bizarre syndromes. Take, for example, a malady called anosagnosia, in which a person denies awareness of a problem he has. People who suffer from right parietal lesions that render them hemiplegic and blind on their left side frequently deny that they have any problem. The left half of their body, they insist, is simply not theirs. They see their paralyzed left hand...
B Peripheral Agraphias
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...
Iii Anomia In Alzheimers Disease
Alzheimer's disease AD is the most studied of the dementia-producing diseases that can have anomia as a salient symptom. Dementia see the article on it in this volume may be defined as a progressive cognitive decline resulting from a number of diseases. Such a cognitive decline characteristically may include more language disturbance as in Alzheimer's disease in all but very-late-onset instances or less language disturbance as in the dementia associated with perhaps one-third of the individuals...
Iii The Caudal Diencephalon
The pretectum alar p1 is the caudalmost forebrain region. It is characterized by the posterior commissure, whose fibers cross the pretectal dorsal midline and then course transversally through the alar plate, just in front of the diencephalomesencephalic limit, before spreading longitudinally in the basal plate pc in Fig. 3 . The function of the posterior commissure is unclear. This region contains various pretectal nuclei involved in visual processing, including the centers for the pupillary...
M Pure Motor Aphasia
Verbal apraxia or pure motor aphasia refers to the articulatory and prosodic disturbance of language output in the absence of the agrammatic component. The underlying lesion is said to involve the left lower motor cortex and posterior operculum. Recently, Nina Dronkers emphasized the relationship between articu-latory deficits and damage to the precentral gyrus of the insula. This clinical syndrome is characterized by impaired articulation, slow and effortful speech, segmentation, phonemic...