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Speciﬁcally buy vasotec in india blood pressure chart age 70, what brain structures are involved in these functions purchase 10mg vasotec free shipping withings blood pressure monitor, how are they connected vasotec 10mg cheap pulse pressure 22, and what are the individual roles of each structure involved? Speciﬁcally, what kind of information is reﬂected in the ﬁring patterns of individual neurons in each component of this functional system? Third, what do we know about the functional organization of the neural networks in these brain areas? That is, how do the neural elements act in concert beyond merely the sum of their independent information-coding properties? In particular, the hippocampal re- gion has been identiﬁed as central to conscious recollection, and the prefrontal cortex as central to the higher-order cognitive functions associated with the development of intentions and plans. This section considers the brain system that encompasses the hippocampal region and prefrontal cortex, as well as other cortical areas, speciﬁcally with regard to their interactions in memory functions. However, it has become clear that there are multiple memory systems in the brain, of which the hippocampal system is only one (Eichen- baum and Cohen, 2001). As Cohen and Squire (1980) ﬁrst recognized, the hippocampal region plays a selec- tive role in declarative memory. By contrast, the hippocampal region is not required for the ac- quisition of a variety of skills and biases that can be expressed unconsciously through alterations in performance on a broad variety of tasks. These kinds of memory are instead mediated by pathways through the neostriatum, cerebellum, amygdala, and other brain areas. Through the use of animal models, we are beginning to characterize the neural circuitry and information-processing mechanisms that mediate the capacity for con- scious recollection. Recent studies have shown that the general pattern of memory deﬁcits and spared capacities following damage to the hippocampal region in mon- keys and rats parallels the phenomenology of amnesia in humans (for a full review, see Squire, 1992; Eichenbaum, 2000). Sensory, motor, motivational, and cognitive processes are intact following hippocampal damage, conﬁrming that this region serves a selective role in memory in animals as it does in humans. A Protocol for Reading the Mind 93 In addition, as in humans, the scope of memory that depends on the hippocampal region in animals is broad but selective to a particular type of memory processing. It is impossible to assess in animals some aspects of declarative memory, such as con- scious recollection. Nevertheless, several studies have been successful in demonstrat- ing a selective role for the hippocampal region in mediating other central features of declarative memory, including the linking of memories within a network of semantic knowledge and ﬂexible, inferential expression of memories, as outlined later. By con- trast, there is abundant evidence that other brain systems in animals mediate other types of learning (for reviews, see McDonald and White, 1993; Eichenbaum and Cohen, 2001). These ﬁndings validate the use of animal models to study memory and set the stage for a detailed neurobiological analysis aimed at identifying the rele- vant pathways and functional mechanisms of the declarative memory system that mediates conscious memory. A Brain System for Conscious Recollection the full system of brain structures that mediate conscious recollection is composed of three major components: cerebral cortical areas, the parahippocampal region, and the hippocampus itself (ﬁgure 5. DG, dentate gyrus; EC, entorhinal cortex; FF, ﬁmbria-fornix; Hipp, hippocampus proper; OF, orbitofrontal cortex; Pir, piriform cortex; PR, perirhinal cortex; Sub, subiculum. They project in di¤erent ways to the parahippocampal region, a set of intercon- nected cortical areas immediately surrounding the hippocampus that in turn project into the hippocampus itself. The main outputs of the hippocampus return to the para- hippocampal region, which sends back projections broadly to the same cortical asso- ciation areas that provided the inputs to the parahippocampal region. This pattern of anatomical organization complements the ﬁndings from studies of amnesia, leading to the working hypothesis that the parahippocampal region and hippocampus make their contributions to memory by altering the nature, persistence, and organization of memory representations within the cerebral cortex. There is emerging evidence that neocortical association areas, the parahippo- campal region, and the hippocampus play distinct and complementary roles in this memory system. The roles of these areas may be best contrasted in the results of studies on a simple recognition memory task, called delayed nonmatch-to-sample (DNMS), where subjects must remember a single stimulus across a variable memory delay. The prefrontal cortex plays an especially important role in the acquisition and im- plementation of task rules. For example, in rats performing an odor-guided version of the DNMS task, damage to the orbitofrontal cortex resulted in a deﬁcit in the ac- quisition of the task when the memory delay was minimal, suggesting an important role in perceptual processing or in learning the nonmatching rule (Otto and Eichen- baum, 1992; Ramus and Eichenbaum, 2000). The prefrontal cortex is parcellated into several distinct areas that have di¤erent inputs and whose functions can be dissoci- ated according to di¤erent modalities of stimulus processing. However, they share common higher-order functions in working memory and strategic processing, which is reﬂected in perseveration and other common strategic disorders following damage to any of the subdivisions (Eichenbaum and Cohen, 2001; Miller, 2000; Fuster, 1995; Goldman-Rakic, 1996). In contrast to the e¤ects of prefrontal damage, rats with damage to the parahippocampal region acquired the DNMS task at the normal rate and performed well at brief memory delays. How- ever, their memories declined abnormally rapidly when the memory delay was ex- tended beyond a few seconds, indicating a selective role in maintaining a persistent memory of the sample stimulus (see also Young et al. Little if any deﬁcit in nonspatial DNMS is observed following damage to the hippocampus or its connec- tions via the fornix, indicating that the parahippocampal region itself mediates the persistence of memories for single items needed to perform the DNMS task. A Protocol for Reading the Mind 95 Parallel results have been obtained in monkeys performing visually guided versions of the DNMS task. Similar to rats, monkeys with damage to the parahippocampal region perform well when the memory delay is brief. However, when the memory demand is increased by extending the delay period, severe deﬁcits in DNMS are observed (Meunier et al. The parahippo- campal region may also play a role in the intersection of perception and memory, in situations where perceptual processes depend on learned associations among com- plex stimulus elements (Eichenbaum and Bunsey, 1995; Murray and Bussey, 1999). The Role of the Hippocampus Itself It is notable that memory mediated by the hippocampus itself contributes very little to performance in standard DNMS tasks, in that the deﬁcits observed are modest at most compared with the e¤ects of damage to the cortex or parahippocampal region. However, the hippocampus may play an essential role in other types of simple recog- nition memory tests (Zola et al. Instead, the ﬁndings from studies using animal models point to a critical role for the hippocampus itself in central aspects of declarative memory. To understand this role, it is important to consider the fundamental properties of declarative memory, as introduced by Cohen and Squire (1980) and subsequently elaborated by many investigators. But the full scope of hippocampal involvement also extends to semantic memory, the body of general knowledge about the world that is accrued by linking multiple experiences that share some of the same information (Squire and Zola, 1998). For example, we learned about our relatives via personal episodes of meeting and talking about family members, and then weaving this information into a body of knowledge constituting our family tree. Similarly, we learned about the geographies of our neighborhood and home town by taking trips through various areas and eventually interconnecting the information in cognitive maps. In addition, declarative memory for both episodic and semantic information is special in that the contents of these memories are accessible through various routes. Most commonly in humans, declarative memory is expressed through conscious, e¤ortful recollection. This means that one can access and express declarative memo- ries to solve novel problems by making inferences from memory. Thus, even without ever explicitly studying your family tree and its history, you can infer indirect 96 Howard Eichenbaum A. In the sample phase, the subject was pre- sented with a cup containing a scented mixture of sand and ground rat chow with a buried reward.
Chapters are highly illustrated and consistently organised generic vasotec 10mg line heart attack 34 years old, reviewing safe vasotec 10mg arterial hypertension, for each pathway discount vasotec 10mg amex arteria oftalmica, the experimen- tal background, methodology, organisation and con- trol, role during motor tasks, and changes in patients withCNSlesions. Eachchapterconcludeswithahelpful resume that can be used independently of the main text´ ´ to provide practical guidance for clinical studies. This is therefore the last word on the role of the spinal cord in human motor control. It will be essential reading for research workers and clinicians involved in the study, treatment and rehabilitation of movement disorders. Emmanuel Pierrot-Deseilligny is Professor of Rehabil- itation and Clinical Neurophysiology at the Hopital deˆ la Salpetriere, University of Paris. T IR IT O S IN ItsRole in M otor Control and M ovem ent Disorders Emmanuel Pierrot-Deseilligny Hopital de la Salpetriereˆ ˆ ` and David Burke University of Sydney cambridge university press Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo Cambridge University Press the Edinburgh Building, Cambridge cb2 2ru,UK Published in the United States of America by Cambridge University Press, New York www. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published in print format 2005 isbn-13 978-0-511-12544-7 eBook (EBL) isbn-10 0-511-12544-5 eBook (EBL) isbn-13 978-0-521-82581-8 hardback isbn-10 0-521-82581-4 hardback Cambridge University Press has no responsibility for the persistence or accuracy of urls for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. In the 1910–1920s Paul Hoffmann demonstrated that percutaneous electrical stimulation of the posterior tibial nerve in human subjects produced a synchro- nised response in the soleus muscle with the same central delay as the Achilles tendon jerk. Subse- quently, much of the primary knowledge about the spinal circuitry has come from animal experiments, but human studies have retained a unique role: the abilitytosheddirectlightonhowspinalmechanisms are used in the control of voluntary movement. Modern views about spinal pathways began to emerge when Anders Lundberg and colleagues showed in the 1960s and 1970s that, in the cat, each set of spinal interneurones receives extensive convergence from different primary afferents and descending tracts, and that the integrative function of spinal interneurones allows the motoneurones to receive a ﬁnal command that has been updated at a premotoneuronal level. Methods have now been developed to enable indirect but nevertheless valid measurements of spinal interneuronal activ- ity in human subjects, and these techniques have demonstrated reliability, particularly when congru- ent results are obtained with independent meth- ods. Their use has allowed elucidation of how the brain modulates the activity of speciﬁc spinal xv xvi Preface interneurones to control movement. This, together ied, (ii) how they are used in normal movement, and with the abnormalities of motor control resulting (iii) how they malfunction in disease states. It is a thesis of this conditions), isometric voluntary contractions have book that the ﬁnal movement is only that part of been the main motor tasks during which changes in thesupraspinallyderivedprogrammethatthespinal transmission in spinal pathways have been investi- cordcircuitrydeemsappropriate. However, recent technological advances now of the spinal cord to generate or sustain even simple allow the investigation of spinal pathways during movements, particularly in human subjects, is lim- naturalmovements,includingreachingandwalking. The motor cortex, it is possible to investigate the corti- recent recording by Eberhard Fetz and colleagues cospinal control of spinal interneurones, but there fromspinalinterneuronesduring,andbefore,volun- are little data for other descending controls from tary movement in the awake monkey well illustrates basal ganglia and the brainstem, other than vestibu- this role of the spinal cord. There techniqueshavebeendevelopedtoallowmoreaccu- has been an explosion of studies on human move- rate probing of spinal pathways in human subjects, ment and of the dysfunction that accompanies dif- providing data that can validate and extend the ﬁnd- ferent neurological disorders, and the prime ration- ings from H reﬂex studies. As a result, knowledge of ale for this book is to summarise the literature the role of spinal pathways in normal and pathologi- related to the control of spinal cord circuitry in cal motor control has increased greatly, and this pro- human subjects. Forexample, ronal circuits can be studied reliably in human sub- the use of post-stimulus time histograms has allowed jects, and no one book can provide a complete the investigation of single motoneurones in human overview of the role of spinal circuitry in normal and subjects, the technique of spatial facilitation allows pathological movement: there are no data for the the exploration of the convergence of different vol- many circuits that cannot yet be studied in human leys on spinal interneurones, and transcortical stim- subjects, let alone the cat. This book is intended to ulation of the motor cortex allows the corticospinal provide a comprehensive account of (i) how some control of spinal pathways to be investigated. This well-recognised and deﬁned circuits can be stud- book details this newer knowledge for the use of Preface xvii those who have an interest in the subject but who been the subject of phylogenetic adaptations have not had time to read the rapidly accumulating to different motor repertoires. Inevitably, there will be inconsis- lower limb, more elaborate reﬂex assistance is tencies in conclusions from studies on intact human required for bipedal stance and gait. Greater has been this phylogenetic adaptation argues validity comes from using a number of independent that spinal pathways have a functional role techniques to demonstrate the same ﬁnding, as is in human subjects and are not evolutionary emphasised in the following chapters. It requires experiments per- Possible future directions for the research are formed during natural movements, as can be discussed. The differ- tributionofhumanstudiestotheunderstanding ent spinal pathways for which there are reliable and of motor control physiology. Thus, even though non-invasive methods of investigation are consid- many of the conclusions are speculative, this ered with, for each pathway: book gives a large place to the probable func- (i) A brief background from animal experiments. The general human subjects, but the validation of a tech- methodologies that are used for investigating path- niqueforexploringagivenpathwaymayrequire ways are considered in a ﬁrst chapter with, for each controls only possible in animal experiments method, its advantages and its disadvantages. There and is more credible when there is a close anal- is a risk that starting with a technical chapter would ogy with animal experiments. This initial chapter is useful to thathavebeenusedtoexploretherelevantpath- understand fully the particular techniques used for ways selectively. Methodological details allow- the investigation of the different pathways, but it ing the reader to use reliable methods are is not essential for comprehension of the following described. The basic organisation of each interpretations were erroneous even if, at the time, pathway may well be the same in humans and inﬂuential, the methods are described in detail, with cats, but the strength of the projections of indi- theirlimitsandcaveats,andtheresultsobtainedand vidual spinal pathways on different motoneu- theirinterpretation(s)arecriticallyevaluatedineach rone pools and their descending control have chapter. Because human studies are fraught with xviii Preface technical difﬁculties, much space has been alloted the ﬁnal two chapters summarise and synthesise to methods and potential pitfalls. It would not have been possible if our wives had not appre- ciated the importance for us of bringing together in a single volume the accumulated knowledge on spinal mechanisms in the control of movement. They have encouraged, supported and tolerated us, understanding even when we were unreasonable, putting life on hold so that we could work. We are greatly indebted to Paolo Cavallari, Jean-Michel Gracies, Hans Hultborn, Lena´ Jami, Stacey Jankelowitz, Elzbieta Jankowska, Dominique Mazevet, Leonor Mazieres, Jens Nielsen, Uwe Proske` and Marco Schieppati who have given generously of their time to read and comment on drafts of various chapters. Above all, particularly special thanks go to Paolo, Lena and Leonor who read the entire text. Finally, the studies summarised in the book represent the intellectual activity of collaborators, colleagues, students and staff. We are grateful to everyone who contributed to these studies, and to our colleagues and their publishers who have allowed us to reproduce Figures from their papers. Finally, the authors would like to thank INSERM and NH&MRC for support of their work. The principle is based on the selective investigation of different spinal path- the apparent simplicity of the monosynaptic projec- ways. Whatever the pathway investigated, its activa- tion of Ia afferents to homonymous motoneurones. We will consider successively: (i) the initial of changes in the spinal circuitry in human sub- ﬁndings; (ii) the principles underlying the mono- jects is therefore to be able to assess changes in synaptic reﬂex testing method; (iii) the basic motoneurone excitability quantitatively, using valid methodology of the H reﬂex; (iv) limitations related reproducible methods. All may be, and many have been, used Initial studies in studies on patients, but here the methodology should be simple and rapid. Animal studies This initial chapter is technical and non-specialist readers could bypass it, referring back if they need the monosynaptic reﬂex depends on the projec- to clarify how results were obtained or understand tion of muscle spindle Ia afferents to homonymous the advantages and limitations of a particular tech- motoneurones and was used in the early 1940s as nique. However, the chapter is required reading for a tool for investigating changes in excitability of those who want to understand fully the particular the motoneurone pool (Renshaw, 1940;Lloyd, 1941). During the 1940s and the monosynaptic reﬂex: H reﬂex early 1950s this method was used to reveal impor- and tendon jerk tant features of the input to spinal motoneurones. Ia afferents from muscle spindle primary endings (dotted line) have monosynaptic projections to motoneurones (MNs) innervating the corresponding muscle (homonymous MNs). The H reﬂex is produced by electrical stimulation of Ia afferents, and bypasses muscle spindles. The tendon jerk is elicited by a tap that stretches muscle spindles and therefore also depends on the sensitivity to stretch of primary endings, a property that may be altered by the activity of efferents (however, see Chapter 3,pp.
The balances among molecular transplantation purchase generic vasotec pills hypertension what is it, did the control group also re- cascades that unfold after an injury present ceive an immunosuppressant agent? After in- prorepair and antirepair possibilities buy cheap vasotec 5mg line arrhythmia books, both ducing a stroke generic vasotec 10mg visa blood pressure screening, did the investigators consider within, near, and remote from the brain or the duration of use of the same anesthetic and spinal cord lesion. What works in one animal model different result, given differences in how such of recovery may not work in another species or drugs alter inhibitory and excitatory neuro- strain, and may have an entirely different ef- transmission for long durations? Coaxing clinically significant portantly, did the investigators perform the regeneration does, however, appear feasible. Marchal G, Beaudouin V, Rioux P, de la Sayette V, techniques for directing the navigational skills Le Doze F, Viader F, Derlon JM, Baron JC. Pro- of cells and their processes, the scaffolds in longed persistence of substantial volumes of poten- their milieu, the most propitious targets, and tially viable brain tissue after stroke: A correlative PET-CT study with voxel-based data analysis. Wu O, Koroshetz W, Ostergaard L, Buonanno F, and specificity of behavioral retraining and en- Copen W, Gonzalez RG. Predicting tissue outcome vironmental experience of the animals in these in acute human cerebral ischemia using combined studies. Molecular, cellular, and systems levels diffusion- and perfusion-weighted MR imaging. Beaulieu C, de Crespigny A, Tong D, Mosely M, Al- upon activity-dependent drives. Longitudinal magnetic resonance ganization that is primed by transplanted cells imaging study of perfusion and diffusion in stroke: and other techniques for neural repair. Hillis AE, Wityk R, Barker P, Beauchamp N, Gail- grow throughout this decade. Subcor- of the causes of failure of acute interventional tical aphasia and neglect inacute stroke: the role of trials for stroke, SCI, and brain trauma, non- cortical hypoperfusion. This approach will settle potentially con- and the fate of the ischemic penumbra. Ann Neu- founding problems such as the applicability of rol 1996; 40:216–226. Activity-dependent learning contributes of the intervention, and biologic and behavioral to motor recovery. Clinical trials ought to draw upon lecular penumbras after focal cerebral ischemia. J the clinical, scientific, and ethical expertise of Cereb Blood Flow Metab 2000; 20:1011–1032. Collat- bilitation experts, medical statisticians, and pa- eral growth and angiogenesis around cortical stroke. Delayed and remote effects of fo- for repair will depend upon the functional in- cal cortical infarctions: Secondary damage and re- corporation of spared and new cells and their active plasticity. In: Freund H-J, Sabel B, Witte O, processes into motor and cognitve networks. Philadelphia: Lippencott- the functional effectiveness of any biologic Raven Publishers, 1997:207–227. Hagemann G, Redecker C, Neumann-Haefelin T, manipulation will require training strategies Freund H-J, Witte O. Increased long-term potenti- developed by rehabilitationists to optimally in- ation (LTP) in the surround of experimentally in- duce activity-dependent plasticity in recon- duced focal cortical infarction. Pharmacologic modulation of recovery after brain injury: a reconsideration of diaschisis. Immediate early gene ex- ments in reaching and the movements of compen- pression in response to cerebral ischemia. Stroke sation in rats with motor cortex lesions: An endpoint, 1996; 27:1682–1687. Emery D, Raghupathi R, Saatman K, Fischer I, hav Brain Res 1991; 42:77–91. Principles of compensation in tein expression suggests a transient increase in re- cognitive rehabilitation. Mechanisms of motor dys- sion after experimental contusive spinal cord injury. Microarray applications in Penumbral probability thresholds of cortical neuroscience. J Neurosurg 1964; 21: New patterns of intracortical projections after focal 385–398. Merzenich M, Recanzone G, Jenkins W, Allard T, Proc Natl Acad Sci USA 2001; 98:3513–3518. Science 1998; ment of the spinal mechanisms underlying spastic- 281:1465–1518. Cai D, Qiu J, Cao Z, McAtee M, Bregman B, Fil- and Advanced Techniques in Clinical Neurophysi- bin M. Brain 2002; 125:1150– associated glycoprotein released from damaged 1161. Lehmann M, Fournier A, Selles-Navarro I, trolled movements in spastic paraparesis. Brain Dergham P, Sebok A, Leclerc N, Tigyi G, McKer- 1997; 120:1621–1633. AMPA/kainate receptor ac- the tendon jerk as a marker of pathological stretch tivation mediates hypoxic oligodendrocyte death and reflex activity in human spasticity. Electrophysiologi- axotomy but not after chronic Schwann cell dener- cal studies of gait in spasticity and rigidity. Movement dysfunction fol- differentiation of olfactory neurons in the adult pri- lowing central nervous system lesions: A problem of mate brain. Turning blood into brain: Cells bearing Biologic Adaptations and Neural Repair 137 neuronal antigens generated in vivo from bone mar- tive processes of synaptic plasticity. The last shall no be first: the ordered focal ischemic infarcts in adult squirrel monkeys. Out of Eden: stem cells and their layed rehabiliative training following a small is- niches. Exp experience on behavioral recovery and neurophysio- Neurol 2001; 172:383–397. Neuronal precursor cells and neuroge- Neurorehabil Neural Repair 2000; 14:187–98. 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The stimuli used to evoke the responses described in this chap- ter were sinusoidal gratings cheap vasotec 5mg without a prescription arteria descendente anterior, single drifting bars buy discount vasotec supine blood pressure normal value, and a random checkerboard pattern vasotec 5 mg online pulse pressure transducer. In the case of gratings, the spatial and temporal frequencies were approximately 0. Twelve equally spaced orientations were tested between 0 and 330 degrees, where 0 degrees was deﬁned as vertical stripes sweeping to the right and 90 degrees was deﬁned as horizontal stripes sweeping from top to bottom. Each oriented stimulus was presented for 3 s, followed by ap- proximately 3 s of a screen uniformly lit at the background intensity. Three hundred trials were performed, giving twenty-ﬁve repeats for each orientation. The orientation for each trial was randomly assigned through a shu¿ing algo- rithm, thereby ensuring that each orientation was tested an equal number of times. The same twelve orientations were tested, but each trial consisted of 64 s of stimulation with a bar, resulting in four passes of the bar, followed by approximately 4 s of a uniformly lit screen at the background inten- sity. Only forty-eight trials were performed, representing four trials at each orienta- tion. Again, the orientation for each trial was selected by a shu¿ing algorithm. Imaging 2-D Neural Activity Patterns 47 the checkerboard pattern consisted of a number of 1:1 Â 1:1-degree squares. Using a pseudorandom number generator, each square was set to one of three inten- sities: white with 15% probability, o¤ with 15% probability, or background with 70% probability. This allowed the entire checkerboard to be shifted both vertically and horizontally by 0. A new checkerboard with a new logical screen o¤set was displayed at a rate of 25 Hz. For all stimuli, the di¤erence between the most intense white and darkest black was selected to give a 50% contrast, with the background intensity set half- way through the intensity range. Data Analysis the optimal orientation was calculated from the drifting sine wave gratings by the method described by Orban (1991). For each orientation tested, a peristimulus time histogram (PSTH) was calculated for the activity recorded on each electrode. The optimal orientation for each multiunit was selected as the orientation giving the largest ﬁring rate for that unit. The recently introduced method of electrophysiological imaging (Diogo et al. In this method, one interpolates activity-level maps for each of the conditions tested; here it was the orientation of a drifting sine wave grating. The condition maps are then combined using the same methods used by the optical imaging community to give a single response map. Their ﬁnding that the map of activity for a single condi- tion is relatively smooth supports the validity of interpolating the condition maps. A reverse correlation method was used to estimate the receptive ﬁeld size and position from the random checkerboard stimulus (Jones and Palmer, 1987; Eckhorn et al. In brief, this method performs a cross-correlation between the occur- rence of a spike and the state of each of the pixels of the computer monitor. Since there is a delay between changing the visual stimulus and the resulting spike, the cross-correlation is typically only examined over a period of 100–20 ms before the spike. After normalization, the result is a three-dimensional array of t-scores, with two of the dimensions representing the vertical and horizontal extent of the computer monitor and the third the latency from the state of the display to a spike. Since the result is presented as a t-score, typically out of a distribution with a very large num- ber of degrees of freedom, the magnitude of the cross-correlation has units of stan- dard deviations. A more complete description of the statistical interpretation of the cross-correlation as well as the spatial and temporal criteria that we apply before accepting a region as being a receptive ﬁeld are detailed elsewhere (Warren et al. Koulakov In this chapter, we deﬁned the receptive ﬁeld to be the contiguous region having a magnitude greater than 4. The size of the receptive ﬁeld was calculated as the area bounded by this region. The location of the receptive ﬁeld was deﬁned as the center of mass of the region. Both the size and position were cal- culated at the latency having the peak magnitude. Fitting Receptive Fields To analyze the visuotopic organization of the primary visual cortex, we compared the position of the receptive ﬁeld with ﬁelds estimated by an a‰ne coordinate trans- formation of the locations of the electrode array onto its visual space representation. The particular a‰ne transformation provides 5 degrees of freedom: magniﬁcation (SFx and SFy), the rotation (y), and translation (OFFa and OFFe). A nonlinear, least-mean-squares minimization method (FMINS function in MATLAB) was used to minimize the di¤erence between the coordinate transform and the measured recep- tive ﬁelds. The electrode position (Ex and Ey) was related to the visual space position by the equation Vh SFx cos y SFy sin y Ex OFFa ¼ þ ; Vv ÀSFx sin y SFy cos y Ey OFFe where Vh and Vv are the horizontal and vertical positions of the receptive ﬁeld in degrees, respectively. We interpreted our results in terms of both linear and confor- mal mapping. For example, a trans- formation on a grid printed on a rubber diaphragm that has been stretched is a conformal operation. Results the use of the UEA requires a new approach to electrophysiological measurements, and it o¤ers distinct advantages and disadvantages over the conventional single- electrode technique. The problem of inserting 100 electrodes simultaneously into the cortex precludes the possibility of positioning each electrode individually so that it is recording optimally from a well-isolated single unit. Rather, the entire array must be rapidly inserted (Rousche and Normann, 1992) to a precisely determined cortical depth. The recordings are then made from the electrodes that have either multiunit or single-unit activity on them. Thus, the number of electrodes having single- or mul- tiunit recording capability varies considerably from experiment to experiment, and the quality of the recordings varies from electrode to electrode in each implantation. Because the position of the electrode cannot be adjusted to optimize recordings, the length of its exposed tip has been increased to improve the likelihood of record- Imaging 2-D Neural Activity Patterns 49 A 100 B 100 50 50 uV 0 uV 0 -50 -50 -100 -100 0 0. Thus the impedances of the UEA electrodes are lower than those of conventional single microelectrodes and range from 200 to 400 kW. Note that for reasons of clarity, only 100 of the 24,000 spikes recorded on this electrode during a half hour trial are shown. Unit classiﬁcation was done by a mixture of Gaus- sian methods (Sahani et al. The size of the single units recorded with the UEA varies substantially from elec- trode to electrode. In this experiment, one electrode recorded single units that had an amplitude of 700 mV. The mean, isolated single-unit amplitude was 110 G 50 mV, and the median single-unit amplitude was 95 mV. Single- versus Multiunit Response Characteristics the recordings described in this chapter were obtained in our best experiment to date. Of the 100 electrodes in the array, only two had unrecordable neural activity, owing to two nonfunctioning channels in our multichannel ampliﬁer. Of the 98 recording electrodes, 29 had clearly visible single units and 57 had isolatable single units using a mixture of Gaussian approaches.
It is not desirable to suppress a productive cough because products list ingredients by generic name buy vasotec 5mg fast delivery blood pressure terms, without identifying the secretions need to be removed proven 5 mg vasotec pulse pressure 62. As a result of these bewildering products buy vasotec once a day blood pressure chart symptoms, tinue to be used and some people report beneﬁcial effects, consumers, including nurses and other health care providers, some research studies indicate that cough medicines are no may not know what medications they are taking or whether more effective than placebos in children or adults. INDIVIDUAL DRUGS Expectorants Individual decongestants, antitussives, expectorants, and mu- Expectorants are agents given orally to liquefy respiratory se- colytics are listed in Drugs at a Glance: Nasal Decongestants, cretions and allow for their easier removal. Guaifenesin is the Antitussives, and Expectorants; selected combination prod- most commonly used expectorant. Several supplements are commonly used to prevent or treat Mucolytics symptoms of the common cold. Mucolytics are administered by inhalation to liquefy mucus in Echinacea preparations differ in chemical composition the respiratory tract. Solutions of mucolytic drugs may be neb- depending on which of the nine species or parts of the plant ulized into a face mask or mouthpiece or instilled directly into (eg, leaves, roots, whole plants) are used, as well as the sea- the respiratory tract through a tracheostomy. Sodium chloride solution and acetylcysteine (Mucomyst) are the only agents recommended for use as mucolytics. Acetylcysteine is effec- tive within 1 minute after inhalation, and maximal effects Nursing Notes: Apply Your Knowledge occur within 5 to 10 minutes. Oral acetylcysteine is widely used in the treatment of acetaminophen overdosage (see Chap. Joan, a college student, comes to the health clinic with cold symptoms (productive cough, low-grade fever, continuous nasal Cold Remedies discharge, and general malaise and discomfort). She states she went to the drugstore to buy some cold medicine, but there were so many different preparations that she was confused. Discuss Many combination products are available for treating symp- your recommendations for Joan, with their underlying rationale. Many of the products contain an CHAPTER 49 NASAL DECONGESTANTS, ANTITUSSIVES, AND COLD REMEDIES 731 Drugs at a Glance: Nasal Decongestants, Antitussives, and Expectorants Routes and Dosage Ranges Generic/Trade Name Adults Children Nasal Decongestants Ephedrine sulfate 0. Maximum, 6 doses/24 h 6–11 y: 2–3 sprays in each nostril no more often than q4h. Maximum 120 mg/24 h 12 y and older: Same as adults Topically, 2–3 sprays or drops of 0. Maximum 60 mg/24 h or 1% solution in each nostril no more often Topically, 2–3 sprays of 0. Pseudoephedrine (Sudafed, Dimetapp) Regular tablets, PO 60 mg q4–6 h 12 y and older: Same as adults for regular and Extended-release tablets, PO 120 mg q12h or extended release tablets 240 mg q24h. Maximum, 60 mg/24 h <2 y: Consult pediatrician Tetrahydrozoline (Tyzine) 0. Nonnarcotic Antitussive Dextromethorphan (Benylin DM, others) Liquid, lozenges, and syrup, 10–30 mg q4–8h. Sustained action liquid, 6–12 y: 30 mg q12h 2–5 y: 15 mg q12h Expectorant Guaifenesin (glyceryl guaiacolate) PO 100–400 mg q4h. Mucolytic Acetylcysteine (Mucomyst) Nebulization, 1–10 mL of a 20% solution or Acetaminophen overdosage, see literature 2–20 mL of a 10% solution q2–6h Instillation, 1–2 mL of a 10% or 20% solution q1–4h Acetaminophen overdosage, PO 140 mg/kg initially, then 70 mg/kg q4h for 17 doses; dilute a 10% or 20% solution to a 5% solution with cola, fruit juice, or water 732 SECTION 8 DRUGS AFFECTING THE RESPIRATORY SYSTEM TABLE 49–1 Representative Multi-Ingredient Nonprescription Cold, Cough, and Sinus Remedies Ingredients Trade Name Antihistamine Nasal Decongestant Analgesic Antitussive Expectorant Actifed Cold & Allergy Triprolidine Pseudoephedrine 2. Also, which constituents of the plants are cause adverse effects and about 90% of large doses is ex- pharmacologically active is unclear. Very little is absorbed and blood levels of Some studies indicating effectiveness of echinacea in vitamin C are raised only slightly. Most of the studies suggesting benefit are consid- controlled study showed no benefit of using echinacea for ered flawed in methodology. For example, although some preventing the common cold or respiratory infection. Thus, there is no convincing evidence that echi- Nursing Process nacea is effective. Moreover, the purity and potency of echinacea products are unknown or variable among prod- Assessment ucts. Vitamin C, usually in large doses of more than 1000 mg • With nasal congestion, observe for decreased ability to daily, is used to reduce the incidence and severity of colds breathe through the nose. However, such usage is not recommended or the amount, color, and thickness. In general, high doses of vitamin C the duration and extent of nasal congestion and factors that demonstrate little or no beneﬁt in shortening the duration of precipitate or relieve the symptom. In addition, they may CHAPTER 49 NASAL DECONGESTANTS, ANTITUSSIVES, AND COLD REMEDIES 733 PRINCIPLES OF THERAPY • With coughing, a major assessment factor is whether the cough is productive of sputum or dry and hacking. If the Drug Selection and Administration cough is productive, note the color, odor, viscosity, and amount of sputum. Single-drug formulations allow ﬂexibility and individ- ualization of dosage, whereas combination products Nursing Diagnoses may contain unneeded ingredients and are more expen- • Risk for Injury related to cardiac dysrhythmias, hyper- sive. However, many people ﬁnd combination products tension, and other adverse effects of nasal decongestants more convenient to use. With nasal decongestants, topical preparations (ie, nasal • Deﬁcient Knowledge: Appropriate use of single- and solutions or sprays) are often preferred for short-term multi-ingredient drug formulations use. They are rapidly effective because they come into direct contact with nasal mucosa. If used longer than Planning/Goals 7 consecutive days or in excessive amounts, however, the client will: these products may produce rebound nasal congestion. Oral agents are • Avoid overuse of decongestants usually contraindicated because of cardiovascular • Avoid preventable adverse drug effects effects (eg, increased force of myocardial contraction, • Act to avoid recurrence of symptoms increased heart rate, increased blood pressure). Antihistamines are clearly useful in allergic condi- Interventions tions (eg, allergic rhinitis; see Chap. First gen- the incidence and severity of symptoms: eration antihistamines (eg, chlorpheniramine, diphen- • Avoid smoking cigarettes or breathing secondhand smoke, hydramine) have anticholinergic effects that may when possible. Cigarette smoke irritates respiratory tract reduce sneezing, rhinorrhea, and cough. Also, their mucosa, and this irritation causes cough, increased secre- sedative effects may aid sleep. Many multi-ingredient tions, and decreased effectiveness of cilia in cleaning the cold remedies contain an antihistamine. Cough associated with the common cold usually stems • Avoid or limit exposure to crowds, especially during win- from postnasal drainage and throat irritation. This is especially important for exert antitussive effects of their own by soothing irri- clients with chronic lung disease because upper respira- tated pharyngeal mucosa. Dextromethorphan is the tory infections may precipitate acute attacks of asthma antitussive drug of choice in most circumstances and is or bronchitis. However, as discussed previously, some authorities • Maintain nutrition, rest, activity, and other general health question the effectiveness of antitussives and do not measures. Ipratropium (Atrovent), an anticholinergic drug, in a • Annual vaccination for influenza is recommended for 0. Cromolyn, a mast cell stabilizer, used by oral or intra- Evaluation nasal inhalation, seems effective in reducing the symp- toms and duration of the common cold but it is not FDA • Interview and observe for relief of symptoms. In one study, it was used • Interview and observe for tachycardia, hypertension, every 2 hours for the ﬁrst 2 days, then 4 times daily. For treatment of excessive respiratory tract secretions, about drug use.
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