By N. Pakwan. The Naval Postgraduate School.
Beyond the issues of designing multisite electrode arrays for the complex geometry and cytoar- chitecture of cortical brain (chapters 3 and 12) it is clear that neural representations of sensory receptive ﬁelds are not static buy lumigan 3ml on-line, but in fact are dynamic purchase 3ml lumigan fast delivery, changing over time viii Preface and with experience (chapter 4) generic 3ml lumigan free shipping. The limitations of using static purchase lumigan 3ml amex, multisite electrode arrays to extract information from a dynamically changing population of neurons must be taken into account when designing neural prosthetic systems triggered by sensory ensemble codes. Sophisticated analyses of multielectrode recordings from the hippocampus in behaving animals (chapters 5 and 6) emphasize the complexity of neural representations typical of memory systems in the brain. Hippocampal neu- rons respond to multiple dimensions (modalities) of a given learning and memory task, with key, higher-level features distributed across populations of spatially dispa- rate cells. How to extract information from systems with such complex functional properties in real time, process that information, and then transmit the processed output back to other parts of the brain to inﬂuence cognitive function and behavior constitutes a considerable challenge. Given the multiple levels of function that characterize the nervous system (i. Chapter 8 o¤ers some practical approaches for how to organize multidimensional time series data to achieve representational schemes for sensorimotor coupling. Despite these complexities, considerable progress is being made in implementing biologically realistic neural system models in hardware. The importance of this step is that, to design and construct a neural prosthetic system that can interact with the brain, the mathematical models required to capture the nonlinear dynamics and non- stationarity of neural functions need to be miniaturized for implantation in the brain or on the skull, and need to take advantage of the parallel processing and high-speed computation o¤ered by microelectronic and optoelectronic technologies. Examples of such ﬁrst steps in very large-scale integration (VLSI) are described here for the hippocampus (chapter 12) and thalamocortical systems (chapter 13). In addition, the use of photonics and holographic technologies for achieving high-density con- nectivity between neural processors (chapter 14) and multiple-pattern storage for context-dependent connectivities and functions (chapter 15) o¤er novel and exciting possibilities for achieving the complexity of neural system functions in hardware. Chapter 16 o¤ers a series of intriguing insights on the potential synergy between neu- roscience and computer engineering; that is, how the capabilities of current VLSI and photonic technologies can facilitate the implementation of biologically based models of neural systems, and how our increasing understanding of neural organization and function can inspire next-generation computational engines. Finally, designing and controlling the interface between neurons and silicon is a critical consideration in the development of central brain neural prostheses. Perhaps most important, the neuron/silicon contacts must be target speciﬁc and maintained for multiyear durations to justify the surgical procedures required for im- plantation. Three chapters (9, 10, and 11) describe some of the latest updates in de- signing neuron/silicon interfaces and o¤er insights into the state-of-the-art problems and solutions for this aspect of implantable biomimetic systems. There were other aspects of the global problem of how to achieve the collective vi- sion of implantable biomimetic neural prostheses that were covered at the original meeting but, unfortunately, they are not readily compatible with a written volume. For example, we considered the need for new graduate education programs to pro- vide next-generation neuroscientists and engineers with the expertise required to ad- dress in the scientiﬁc, technological, and medical issues involved, and discussed the technology transfer and commercialization obstacles to realizing a viable medical de- vice based on an interdisciplinary science and technology foundation for implantable neural prostheses. Loeb Neurons and modern digital electronic devices both process information in the form of all-or-none impulses of electricity, respectively called action potentials and logical states (bits). Over the past 50 years, electrophysiological techniques have been developed to provide sophisticated, safe, and reliable interfaces between elec- tricity carried as ion ﬂuxes in water and electricity carried as electron motion in metal conductors. Neural prostheses consist of the use of such interfaces to replace or repair dysfunction in the human nervous system. This chapter reviews the promises and the reality of what has been and might be achieved in the areas of sensory and motor prostheses, in the hope of providing some useful lessons and strategies for undertaking even more ambitious projects to repair higher neural functions such as cognition, memory, and a¤ect. Let us start with some examples drawn from other ﬁelds and then try to relate this categorization to actual or potential neural prostheses in order to understand their technical feasibility, clinical potential, and strategic risk. In fact, theoreti- cal feasibility has been demonstrable for over a century, but practical achievement required a lot of technology, time, and money. At some point between Jules Verne and the Apollo missions, putting a man on the moon shifted from ﬁction to nonﬁction. I submit that the point occurred when some- one, probably early in the history of modern rocketry, actually performed the myriad 4 Gerald E. Loeb calculations related to gravity ﬁelds, rocket acceleration, fuel e‰ciency, life-support systems, etc. In contrast, curing most cancers remains in the category of scientiﬁc research rather than engineering or clinical practice because we still do not know enough about what causes cancer or how cells control their reproduction to even identify a particular strategy for curing cancer in general. One can construct plausible scenarios for how it might be possible to cure cancer, but they must be based on suppositions or hypotheses about how cells work that are as yet unproven. They are particularly pernicious lies if one tells such stories to patients and their families, who would like to believe and use them as a basis for important personal decisions on alternative methods of treatment and rehabilitation.
Similarly cheap 3 ml lumigan with amex, sural nerve stim- During spinal shock order 3ml lumigan otc, withdrawal reﬂexes are abol- uli below pain threshold produce inhibition in the ished generic 3 ml lumigan free shipping. Finally buy lumigan 3ml amex, some 2– The grasp reﬂex observed in patients with frontal 6 months after the initial injury when the lesion lobe lesions is due to the summation of two local is chronic, early responses are suppressed and re- reﬂexes: an early cutaneous reﬂex followed by a placed by long-latency responses. In patients with stretch reﬂex of ﬁnger ﬂexors, the latter ineffective a chronic spinal cord injury, withdrawal responses in the absence of the former. The RII reﬂex evoked have an invariant pattern of ﬂexion, regardless of the in wrist and elbow ﬂexors by cutaneous afferents stimulus location on the foot or leg. With mechanical stimuli, the patho- periods are abnormally brief or virtually absent; logicalresponseinvolvestherecruitmentofextensor and (iv) habituation is less evident than normal. The pathophysiology of the Babin- Transcortical inhibitory responses (I1) in intrinsic ski response involves the suppression of the nor- muscles of the hand are suppressed with respect to mal segmental reﬂex plantar ﬂexion and disinhibi- normal subjects. Accordingly, the upward response of toe 1 will be accompanied by activation of other muscles of the Abbruzzese, G. Task- dependent effects evoked by foot muscle afferents on leg ﬂexor synergy. Electroencephalography and ski sign may be due to a pressure palsy of the pero- Clinical Neurophysiology, 101, 339–48. London:Perg- (iii) Alterations of lower limb withdrawal reﬂexes amon Press. Muscleand involved, decreased threshold, delay or suppression Nerve, 22, 1520–30. Reﬂexresponses of early reﬂex components, and dishabituation of in active muscles elicited by stimulation of low threshold reﬂex activity. JournalofNeurophysiology, (iv) Flexor spasms are due to an overly vigorous 67, 1375–84. Du phenomene´ ` des orteils et sa valeur talinputs,andhavethesameclinicalandphysiologi- semiologique. In Handbook of Physiology, 446 Cutaneomuscular and withdrawal reﬂexes sectionI,TheNervousSystem,vol. Federation Proceed- Evidencesuggestingthatatranscorticalreﬂexpathwaycon- ings, 41, 2907–18. Evidence for transcortical reﬂex path- the evolution of function in the nervous system. An investigation upon the plantar reﬂex, with changesintheresponsestolow-thresholdcutaneousaffer- reference to the signiﬁcance of its variations under patho- ent volleys in the human lower limb. Journal of Physiology logical conditions, including an enquiry into the aetiology (London), 432, 445–58. Journal of Physiology (London), 318, reﬂexes as a tool to investigate the organization of spinal 501–10. Acom- lower limb motoneurons in man: spinal and supraspinal parisonofperipheralandrubrospinalsynapticinputtoslow contributions. Cutaneous nerve stimulation and motoneuronal iology (London), 207, 709–32. Long latency¨ ﬂexor carpi radialis H-reﬂex following tactile stimulation responses in human thenar muscles mediated by fast of the index ﬁngertip. Experimental Brain Research, 120, conducting muscle and cutaneous afferents. Electrophys- relations between long-latency reﬂexes in hand muscles, iologic analysis of the motor system after stroke: the ﬂexor somatosensory evoked potentials and transcranial stimu- reﬂex. Phasic control of reﬂexes from the dorsum of the paw extremity of hemiparetic subjects. Journal of Neurology, tral pathways responsible for depolarization of primary Neurosurgery and Psychiatry, 26, 39–50. CentralEMG eral ﬂexor nor a withdrawal pattern of nociceptive reﬂexes and tests of motor control. Neuroscience Research, 37, Electroencephalography and Clinical Neurophysiology, 90, 79–82. Habituation dependent changes in cutaneous reﬂexes recorded from of cutaneomuscular reﬂexes recorded from the ﬁrst dorsal various muscles controlling ﬁnger movement in man. Phase-dependentmodulationofcutaneousreﬂexes organizationofinterneuronestransmittingeffectsfromthe of tibialis anterior muscle during hopping.
Details are described in the com- developmental anteroposterior canal diameter of the cer- plications section buy lumigan 3 ml on line. The incidence of neck pain after lamino- than that in white Western populations discount 3 ml lumigan overnight delivery. The pathomechanism of postoperative neck discomfort has not yet been clar- Aims purchase 3 ml lumigan amex, advantages cheap 3 ml lumigan visa, and disadvantages of laminoplasty ified, although several hypotheses have been advocated such as prolonged neck immobilization, facet joint dam- Aims age, and nuchal muscle damage. Although The aims of laminoplasty are to expand the spinal canal, preservation of spinal mobility is one of the aims of lamino- to secure spinal stability, and to preserve the protective plasty, the range of motion (ROM) usually decreases by function of the spine. The spared laminae pre- serve the protective function of the spine, shielding the Laminoplasty is indicated for myelopathy secondary to: spinal cord from pressure from hematoma during the early – Developmental spinal canal stenosis (an anteroposterior postoperative period and preventing the invasion of scar canal diameter less than 13 mm) tissue subsequent to hematoma in the late convalescent – Continuous or mixed type of OPLL period. Development of kyphosis in combination with a – Multisegmental spondylosis associated with a relatively thick peridural scar following laminectomy is a notorious narrow spinal canal(13–14 mm) [32, 35] cause of late neurological deterioration in laminectomy. Basically, no instrument needs to be inserted into the be lessen postoperative kyphosis and instability. Furthermore, the site of the lamino- plasty with stabilization (fusion) has been widely indi- 115 cated for myelopathy secondary to multilevel subaxial further details of other procedures, the reader is referred subluxation in patients with rheumatoid arthritis. At present, no type of laminoplasty can correct a fixed The patient is placed in the prone position on a laminec- kyphotic deformity into a lordotic curve. Suda and his coauthors reported ommended to secure the head and maintain cervical align- that patients having local kyphosis exceeding 13° showed ment in the neutral position or slight extension. When spi- poor surgical results and recommended anterior surgery or nal fusion is required, the cervical spine is adjusted to its posterior decompression with correction of kyphosis. For (radiculo)myelopathy secondary to multisegmental Through a posterior midline incision, the nuchal liga- spondylosis associated with athetoid cerebral palsy, ment is divided at the midline. Typically, in CSM, the ex- laminoplasty combined with a proper fusion procedure tent of decompression is from C3 to C7 for complete pos- can be indicated, provided that the athetoid movements of terior migration of the spinal cord. Decompression should the neck can be properly controlled with a halo vest in the also be wide enough for the spinal cord to migrate poste- postoperative period. When an ossified lesion extends up to C2, under- Laminoplasty can be indicated for myelopathy sec- cutting of the C2 lamina (dome-shaped laminoplasty) or a ondary to soft disc herniation when the condition is asso- spinous process splitting type of laminoplasty is added. Spontaneous withdrawal of disc fragments after laminoplasty has been reported. Unilateral hinge laminoplasty (Hirabayashi) For the expansive open-door laminoplasty of Hirabayashi Techniques of laminoplasty [7, 9], the spinous processes are exposed from C2 to T1, and supplementary procedures with care being taken not to damage the supraspinous and interspinous ligaments. After exposure of the laminae from Although several types of laminoplasty have been reported, C2 to T1, a gutter is made at the junction of the articular most of them can be classified into two types: the open- processes and the laminae. We employ a steel burr to cut door type of Hirabayashi and the French-door type of the outer cortex and cancellous bone of the laminae, and Kurokawa. The basic concept of most of procedures then make the inner cortex progressively thinner using a is similar to one of these two procedures (Fig. With adequate irrigation and suction, the these two procedures are described in more detail. For color of the cortex can be seen to change from ivory to dark red as the epidural venous plexus becomes evident. The cranial part of each lamina is thicker than the caudal part and is covered by the caudal portion of the lamina above, so it needs more grinding than the caudal part to equalize the thickness of the inner cortex. Then a scalp clip holder is inserted into the gutter and opened to sepa- rate both edges of the gutter by fracturing the thinned in- ner cortex. After laminotomy, another gutter is made on the hinge side with a steel burr, being set more laterally than the gutter on the opening side. Opening of the laminae is secured by sutures placed on the facet joint capsules on the hinge side and the corresponding laminae. If the lifted laminae are not fixed firmly, loss of en- largement of the spinal canal can occur. In order to avoid this loss, a prop bone graft from C7 and T1 spinous pro- cess supporting the lifted lamina was devised by Itoh and Tsuji, known as en-bloc laminoplasty. If spinal fusion is required, a block bone graft from the ilium is placed to bridge the segments to be fused and is secured with wire. In the spinous process splitting laminoplasty of Kurokawa, the dorsal part of each spinous process is removed and the fragments are used as bone grafts in the space Postoperative management made by spinous process splitting. Gutters for the hinge are produced as in the expansive open-door laminoplasty.
Different references give you dif- with speciﬁc disease processes and may thereby facilitate ap- ferent information and are organized differently effective lumigan 3 ml. Helpful Inter- book of pharmacology is comprehensive and gives you enough net sites include the Food and Drug Administration (http:// information to understand how drugs work purchase lumigan 3ml online. Drug handbooks are helpful when you are trying to research speciﬁc information about a speciﬁc drug purchase lumigan 3ml otc. They are arranged alphabetically and as- STRATEGIES FOR STUDYING sume you have a basic understanding of pharmacology purchase 3 ml lumigan. It provides the reader with drug inserts from the manufacturer and color photographs of 1. Much information is provided, but without prioritization (eg, any reported side effect is given rather than opioid analgesics (see Chap. Understanding mor- identifying the most common or most serious side effects), which phine makes learning about other opioid analgesics can make it difﬁcult for a beginning student to use effectively. Changing the status of drugs from prescription to over- the-counter availability. Discuss mechanisms and potential effects of by which drugs cross biologic membranes and drug–drug interactions. Green, an 89-year-old widow, lives alone and has recently started taking many heart medications. She prides herself on being independent and able to manage on her own despite failing memory and failing health. When you visit as a home health nurse, you assess therapeutic and adverse effects of her medications. What psychosocial factors could affect the therapeutic and adverse effects of Mrs. What data will be important to collect before developing a plan for Mrs. When clients are taking many medications, the risk for drug interactions and toxicity increases. Describe how you will develop a plan to research possible drug interactions for any client. OVERVIEW and mechanisms of drug transport, pharmacokinetics, phar- macodynamics, and other basic concepts and processes. These All body functions and disease processes and most drug ac- concepts and processes form the foundation of rational drug tions occur at the cellular level. They can stimulate or inhibit normal cellular functions and activities; they cannot add func- tions and activities. To act on body cells, drugs given for sys- CELLULAR PHYSIOLOGY temic effects must reach adequate concentrations in blood and other tissue ﬂuids surrounding the cells. That the body and be circulated to their sites of action (target cells). Although cells differ from one tissue to another, their these questions are derived from cellular physiology, pathways common characteristics include the ability to: 9 10 SECTION 1 INTRODUCTION TO DRUG THERAPY distribution, metabolism (biotransformation), and excretion. Cell Overall, these processes largely determine serum drug levels, membrane onset, peak and duration of drug actions, drug half-life, ther- Cytoplasm apeutic and adverse drug effects, and other important aspects of drug therapy. Lysosomes Chromatin Nucleus Absorption Endoplasmic reticulum Absorption is the process that occurs from the time a drug en- Ribosomes ters the body to the time it enters the bloodstream to be cir- culated. Onset of drug action is largely determined by the rate Golgi apparatus of absorption; intensity is determined by the extent of ab- sorption. Numerous factors affect the rate and extent of drug Mitochondria absorption, including dosage form, route of administration, blood ﬂow to the site of administration, GI function, the pres- Figure 2–1 Schematic diagram of cell highlighting cytoplasmic ence of food or other drugs, and other variables. An intravenous drug is virtually 100% bioavailable; an oral drug is virtually always less than • Exchange materials with their immediate environment 100% bioavailable because some is not absorbed from the GI • Obtain energy from nutrients tract and some goes to the liver and is partially metabolized • Synthesize hormones, neurotransmitters, enzymes, struc- before reaching the systemic circulation. Liquid medications are absorbed faster than tablets or capsules because they need not be dissolved.
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