S. Connor. Oberlin College.
We provide evidence from peripheral and SI recordings that the high frequencies effective malegra dxt plus 160mg erectile dysfunction treatment adelaide, in the hundreds of Hertz (Hz) buy malegra dxt plus 160mg low cost impotence grounds for annulment philippines, transmitted by vibrissae at their funda- mental resonance frequency can drive high ﬁdelity neural activity. These ﬁndings suggest that a volley principle may exist in the transmission of high resolution temporal signals from the periphery. Speciﬁcally, the sensitivity of this system to high velocity vibrissa motion, and the high degree of direction tuning observed in many trigeminal neurons, suggest that an inherent frequency doubling may occur through the convergence of signals from direction-tuned peripheral neurons. In the ﬁnal section of this chapter, we summarize the main ﬁndings and give a brief discussion of how the principles described here may relate to human tactile perception. THE BEHAVIORAL RELEVANCE OF HIGH FREQUENCY SOMATOSENSORY PERCEPTION Frequency information approximately tens of Hz to over a kHz is essential to accurate sensory processing in the auditory, somatosensory, and visual domains. The soma- tosensory system employs frequency-speciﬁc information in a variety of perceptual contexts. Vibratory stimuli transmitted through solid media provide an important sensory input to a variety of mammalian species. For example, blind moles are known to seek out conspeciﬁcs and termite colonies using primarily vibratory cues transmitted through the ground. High frequency, temporally varying information also directly beneﬁts human tactile perception. Surface perception in humans may employ temporally varying signals related to vibration perception. While spatially intensive cues dominate the judgment of roughness for surfaces with a periodicity in the range of ~1–3 mm,4,5 temporal frequency information likely contributes to the judgment of spatial © 2005 by Taylor & Francis Group. For example, robust tactile apparent motion illusions can be evoked when speciﬁc frequencies of stimulation, typically ≥50 Hz, are applied either sequentially across a series of three or more contact points or in bursts applied to >2 contact points. Cockroaches can discriminate between laminar airﬂow of the type generated by wind from turbulent airﬂow of the type generated by an overhead predator using their cercal sensillae,12,13 and special- ized mechanical organs in the leg may be used to respond to sound stimuli. SENSORY CAPABILITIES OF THE VIBRISSA SENSORY SYSTEM Different kinds of mammals, ranging from seals to chinchillae, employ long facial hairs (vibrissae) to obtain sensory information. In rats and mice, the lateral posterior surface of the face is covered with an orderly array of rows and arcs of vibrissae that are typically identiﬁed by letters (rows) and numbers (arcs). The longest vibris- sae are located most posterior and are referred to as the macrovibrissae, and smaller microvibrissae are grouped more anteriorly in a dense patch. Although microvibris- sae are likely important for perception,16,17 especially of objects a rat is about to attempt to eat, they have received markedly less study. Because of this, references to vibrissae throughout the chapter will indicate the macrovibrissae only, although many of the observations described below should also apply to microvibrissae. As suggested by the name vibrissa, mammals are capable of performing high- resolution frequency-related tasks with these sensors. With regards to airborne stim- uli, rats can discriminate between different frequencies presented with an oscillating air stream. Rats can also use their vibrissae to discriminate between periodic gratings with a spacing of 1. For this kind of discrimination, two vibrissae, isolated to the same row, were minimally required. THE VIBRISSA RESONANCE HYPOTHESIS Sensory stimuli transmitted through airborne, liquid and solid media interacting with the vibrissae likely generate high frequencies of vibrissa vibration. In the case of the textures employed in behavioral tasks, estimates ranging from 200 Hz to over 1 kHz have been suggested for the rate of vibration generated when a rat sweeps its vibrissae over these surfaces. As described in this chapter, we hypothesize that vibrissa resonance may play a crucial role in frequency-speciﬁc transduction of tactile sensory information. In the following section, we provide background on other systems that are believed to employ resonance in the transduction of sensory input, followed by a more explicit statement of the vibrissa resonance hypothesis. Resonance and Frequency Encoding in Other Sensory Systems For any given object, there exists a speciﬁc set of frequencies that, when applied, will cause the object to demonstrate a larger relative amplitude of vibration. This property is known as resonance and can be observed in several common contexts. The largest resonance ampliﬁcation is observed when stimuli are applied at the fundamental resonance frequency, but other higher harmonics are also observed and also amplify object motion. Larger amplitudes of motion applied at a given frequency also create larger velocities an important consideration for processing in the vibrissa sensory system. The vibrissa resonance hypothesis follows a long line of similar proposals made for other sensory transduction systems. According to Wever, the ﬁrst suggestion that the resonance properties of a transduction organ facilitate frequency-speciﬁc repre- sentation was made by Bauhin in 1605, with the proposal that the cavities of the inner ear resonate to enable sound representation.
They were instructed to move the valid hand that they could see at the place of the impaired arm malegra dxt plus 160 mg visa impotence divorce. Following a series of 24 daily visuomotor training sessions 160mg malegra dxt plus with amex erectile dysfunction oral treatment, the activity of the M1 area contralateral to the impaired (paralyzed) arm, monitored by fMRI, was greatly increased. This result shows that observation of a normally moving limb can activate the motor area controlling the homologous limb in the observer. A possible explanation for this phenomenon is that mirror neurons similar to those found in the monkey premotor cortex are activated by observation of the Copyright © 2005 CRC Press LLC moving hand and trigger the activity of M1 neurons innervating the impaired hand. In these two patients, this visuomotor training procedure had a beneﬁcial effect, not in improving their hand movements, which remained impaired due to the plexus brachial lesion, but in decreasing their phantom limb pain. This effect suggests that the motor cortex, in addition to its role in controlling movements, may also inﬂuence the processing of sensory input arising from the effector it controls. The ability of human subjects to imitate each other derives from the possibility of forming action representations from the observation of other people. According to this hypothesis, brain areas that become active during execution of a movement should become more active when that movement is elicited by the observation of an identical movement made by another person. Areas in the left inferior frontal cortex and in the parietal cortex seem to fulﬁll this requirement. This result, showing that brain areas for execution and observation of a movement are matched, is compatible with the simulation theory. Furthermore, it raises again the point (already raised in the section about shared representations) of how two different representations of the same action are disen- tangled from one another. Other studies dealing with imitation71 suggest that areas might be activated differently whether an action is internally produced or generated by another agent. First, because all aspects of action appear to be involved during action repre- sentation, it seems a logical consequence of this rehearsal of the corresponding brain structures, and speciﬁcally the motor structures, that the subsequent execution will be facilitated. The presence of activity in the motor system during covert action puts the action representation in a true motor format, so that it can be regarded by the motor system as a real action. In addition, imitation seems to be based on directly matching the observed action onto an internal simulation of that action. Second, activation of the motor cortex and of the descending motor pathway seems to fulﬁll several critical functions. First, this activation contributes to gener- ating corollary signals that propagate upstream to the parietal and premotor cortices. This mechanism would allow for evaluating the potential consequences of the future action. The well-known “antisaccade” task and its analogues in reaching serve as special cases of such transformational mapping, one form of nonstandard mapping. Other forms of nonstandard mapping differ from both of the above: they are arbitrary. Here we explore several types of arbitrary mapping, with emphasis on the neural basis of learning these behaviors. Like braking at a red trafﬁc light, Pavlovian learning depends on an arbitrary Copyright © 2005 CRC Press LLC relationship between a response and the stimulus that triggers it. The example of braking at a red light, but accelerating at a yellow one, serves as a prototypical (and sometimes dangerous) example of such behavior. In the laboratory, this kind of task goes by several names, including conditional motor learning, conditional discrimination, and stimulus–response conditioning. One stimulus provides the con- text (or “instruction”) for a given response, whereas other stimuli establish the contexts for different responses. The importance of arbitrary sensorimotor mapping is well recognized — a great quantity of animal psychology revolves around stimulus–response conditioning — but the diversity among its types is not so well appreciated. On the surface, this behavior seems to depend on a straightforward stimulus–response mechanism. The mechanism comprises an input, the red light, a black box that relates this input to a response, and the response, which consists of jamming on the brakes. Using the mechanism described above, a person makes a braking response in the context of the red light regardless of the predicted outcome of that action3 and without any consideration of alternatives. Experiments on rodents sometimes entail the assumption that all stimulus–response relationships are habits.
We have shown how artificial neural networks with their ability for self-organization of non-crisp data provide an almost natural link between the hard computational world and the soft-computing of the human brain buy malegra dxt plus 160mg with mastercard erectile dysfunction pills australia. We believe that interactive information retrieval methodologies that account for the rich context of natural language will significantly contribute to knowledge acquisition through text analysis buy 160mg malegra dxt plus with amex erectile dysfunction 32. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. Knowledge representation and retrieval using conceptual graphs and free text document self-organisation techniques. Efficient literature searching: A core skill for the practice of evidence-based medicine. Integrating query of relational and textual data in clinical databases: A case study. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. Interactive Information Retrieval Towards Effective Knowledge Management 69 Hearst, M. Proceedings of 19th ACM International Conference on Research and Development in Information Retrieval (pp. Indexing biomedical documents: From thesaural to knowledge- based retrieval systems. Text categorization with support vector machines: Learning with many relevant features. Special Issue on Neural Networks for Data Mining and Knowledge Discovery, 574-585. Proceedings of the 7th World Multiconference on Systemics, Cybernetics and Informatics, July (pp. Annual Conference of the American Medical Informatics Association (AMIA), 445-449. Power of expression in the electronic patient record: Structured data or narrative text? Copying or distributing in print or electronic forms without written permission of Idea Group Inc. Understanding and using the medical subject headings (MeSH) vocabulary to perform literature searches. Towards routine automatic pathway discovery from on-line scientific text abstracts. GeneWays: A system for extracting, analyzing, visualizing, and integrating mo- lecular pathway data. Spatialization methods: A cartographic research agenda for non-geographic information visualization. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. Interactive Information Retrieval Towards Effective Knowledge Management 71 Spyrou, S. Exploring the degree of concordance of coded and textual data in answering clinical queries from a clinical data repository. An interactive system for finding complementary literatures: A stimulus to scientific discovery. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. This chapter provides an overview of some of the daily privacy and security issues currently faced by health services, as health knowledge system developments risk outpacing medico-legal and professional structures. The focus is a mixture of philosophy and pragmatics with regard to the key “privacy” and “security” issues that challenge stakeholders as they try to implement and maintain an increasing array of electronic health knowledge management systems. The chapter utilises a number of evolving simple visual and mnemonic models or concepts based on observations, reflections and understanding of the literature.
Lopinavir–Ritonavir In the United States generic malegra dxt plus 160mg mastercard wellbutrin xl impotence, the Centers for Disease Lopinavir is available in the United States only as a Control recommend that HIV-infected mothers avoid ﬁxed-dose combination with ritonavir (Kaletra) malegra dxt plus 160mg on line impotence kidney disease. In this breast-feeding to prevent the transmission of the virus regimen, a low dose of ritonavir is used to inhibit the to their infants. Side effects, mission ranges from 5 to 20%; longer durations of which are generally mild, include diarrhea, nausea, as- breast-feeding, mastitis, and abscesses are associated thenia, and headache. In developing countries in which Ritonavir is a potent inhibitor of CYP3A4 and also in- safe infant formula is not readily available, the avoid- hibits CYP2D6. The fenone, pimozide, and rifampin should not be given with World Health Organization recommends that under lopinavir–ritonavir combination therapy. The mechanism of action of lamivudine differs from been taking zidovudine and abacavir for the past 3 that of efavirenz in that years to treat HIV infection. These factors put her (A) Lamivudine inhibits HIV protease; efavirenz at high risk for drug-induced inhibits reverse transcriptase. She has a history of alcohol abuse and has of diazepam overdose, including grogginess and 594 VI CHEMOTHERAPY difﬁculty waking and maintaining consciousness. Diazepam is metabolized in the liver by diazepam CYP3A4 and CYP2C19; efavirenz inhibits both of (B) Efavirenz competes with diazepam for renal these isozymes and is likely to increase plasma lev- elimination els of diazepam. Diazepam is almost completely (C) Lamivudine potentiates the depressant activity converted to inactive metabolites; therefore, renal of diazepam elimination is not much of a concern. Lamivudine (D) Zidovudine induces the metabolism of di- may produce fatigue as a side effect but does not azepam potentiate the depressant activity of diazepam. Myelotoxicity is associated with certain NRTIs (A) Central fat accumulation and peripheral fat such as zidovudine. Fat redistribution, drug interac- wasting tions involving CYP3A4, dyslipidemia, and diabetic (B) Drug interactions involving cytochrome P450 symptoms are all side effects common to the pro- enzymes tease inhibitors. Ritonavir is a potent inhibitor of CYP3A4, the (D) Hypercholesterolemia and hypertriglyc- enzyme that rapidly inactivates lopinavir. This com- eridemia bination includes a low dose of ritonavir that is not (E) Hyperglycemia and insulin resistance likely to cause serious side effects but instead in- 5. Lopinavir is almost completely (A) Ritonavir and lopinavir inhibit HIV reverse eliminated by metabolism to inactive metabolites; transcriptase in different ways little is eliminated unchanged by the kidney. Lopinavir inhibits the enzyme HIV pro- (C) Ritonavir decreases the renal elimination of tease, not a structural protein. Non-nucleoside HIV-1 reverse tran- scriptase (RT) inhibitors: Past, present, and future ANSWERS perspectives. Risk factors associated with utilization of viruses in the latent reservoir for hu- the development of this syndrome include female man immunodeﬁciency virus type 1. Hyperuricemia is not associated with verse transcriptase gene can inﬂuence the clinical these risk factors. During this time, his CD4 sulting in the loss of virological response and possi- count raised from 200 cells/mm3 to 725 cells/mm3. R returned to his physician it appears that saquinavir was no longer present at with a severe herpes outbreak on one side of his an effective concentration and the HIV virus be- face. Many antidepressants are metabo- wort is a potent inducer of intestinal and hepatic lized by cytochrome P450 systems; thus, a reduction CYP3A4. Saquinavir undergoes extensive ﬁrst-pass in antidepressant dosage may be necessary because metabolism by intestinal CYP3A4 and is metabo- NNRTIs and protease inhibitors inhibit cytochrome lized in the liver by CYP3A4. Slagle DRUG LIST GENERIC NAME PAGE GENERIC NAME PAGE Amphotericin B 596 Miconazole 600 Butoconazole 601 Naftiﬁne hydrochloride 602 Capsofungin 601 Nystatin 598 Ciclopirox 602 Oxiconazole nitrate 601 Clotrimazole 600 Sulconazole nitrate 601 Econazole 601 Terbiniﬁne hydrochloride 602 Fluconazole 598 Terconazole 601 Flucytosine 601 Tioconazole 601 Griseofulvin 602 Tolnaftate 602 Itraconazole 599 Undecylenic acid 602 Ketoconazole 599 Voriconazole 600 Fungal infections are usually more difﬁcult to treat seated or disseminated fungal infections caused by di- than bacterial infections, because fungal organisms grow morphic fungi, the yeasts Cryptococcus neoformans, and slowly and because fungal infections often occur in tis- various Candida spp. Therapy of fungal ene), amphotericin B liposomal preparations, ﬂucyto- infections usually requires prolonged treatment. Poten- sine (a pyrimidine antimetabolite), the newer azoles, in- tially life-threatening infections caused by dimorphic cluding ketoconazole, ﬂuconazole, itraconazole and fungi are becoming more common because increasing voriconazole, and capsofungin (an echinocandin). Superﬁcial fungal infections involve cutaneous sur- Chemistry and Mechanism of Action faces, such as the skin, nails, and hair, and mucous mem- brane surfaces, such as the oropharynx and vagina. A Amphotericin B (Fungizone), a polyene antifungal drug growing number of topical and systemic agents are produced by the actinomycete Streptomyces nodosus, available for the treatment of these infections. Deep- consists of a large ring structure with both hydrophilic 596 52 Antifungal Drugs 597 and lipophilic regions. Polyene antifungal drugs bind to are not elevated in renal or hepatic failure, and the drug the fungal cell membrane component ergosterol, lead- is not removed by hemodialysis. Amphotericin has Clinical Uses a lesser afﬁnity for the mammalian cell membrane com- ponent cholesterol, but this interaction does account for Amphotericin B is most commonly used to treat serious most adverse toxic effects associated with this drug.
9 of 10 - Review by S. Connor
Votes: 85 votes
Total customer reviews: 85