980 resultados para Anatomy.


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The effects of practice on the functional anatomy observed in two different tasks, a verbal and a motor task, are reviewed in this paper. In the first, people practiced a verbal production task, generating an appropriate verb in response to a visually presented noun. Both practiced and unpracticed conditions utilized common regions such as visual and motor cortex. However, there was a set of regions that was affected by practice. Practice produced a shift in activity from left frontal, anterior cingulate, and right cerebellar hemisphere to activity in Sylvian-insular cortex. Similar changes were also observed in the second task, a task in a very different domain, namely the tracing of a maze. Some areas were significantly more activated during initial unskilled performance (right premotor and parietal cortex and left cerebellar hemisphere); a different region (medial frontal cortex, “supplementary motor area”) showed greater activity during skilled performance conditions. Activations were also found in regions that most likely control movement execution irrespective of skill level (e.g., primary motor cortex was related to velocity of movement). One way of interpreting these results is in a “scaffolding-storage” framework. For unskilled, effortful performance, a scaffolding set of regions is used to cope with novel task demands. Following practice, a different set of regions is used, possibly representing storage of particular associations or capabilities that allow for skilled performance. The specific regions used for scaffolding and storage appear to be task dependent.

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Reading and listening involve complex psychological processes that recruit many brain areas. The anatomy of processing English words has been studied by a variety of imaging methods. Although there is widespread agreement on the general anatomical areas involved in comprehending words, there are still disputes about the computations that go on in these areas. Examination of the time relations (circuitry) among these anatomical areas can aid in understanding their computations. In this paper, we concentrate on tasks that involve obtaining the meaning of a word in isolation or in relation to a sentence. Our current data support a finding in the literature that frontal semantic areas are active well before posterior areas. We use the subject’s attention to amplify relevant brain areas involved either in semantic classification or in judging the relation of the word to a sentence to test the hypothesis that frontal areas are concerned with lexical semantics and posterior areas are more involved in comprehension of propositions that involve several words.

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The mammalian immune system must specifically recognize and eliminate foreign invaders but refrain from damaging the host. This task is accomplished in part by the production of a large number of T lymphocytes, each bearing a different antigen receptor to match the enormous variety of antigens present in the microbial world. However, because antigen receptor diversity is generated by a random mechanism, the immune system must tolerate the function of T lymphocytes that by chance express a self-reactive antigen receptor. Therefore, during early development, T cells that are specific for antigens expressed in the thymus are physically deleted. The population of T cells that leaves the thymus and seeds the secondary lymphoid organs contains helpful cells that are specific for antigens from microbes but also potentially dangerous T cells that are specific for innocuous extrathymic self antigens. The outcome of an encounter by a peripheral T cell with these two types of antigens is to a great extent determined by the inability of naive T cells to enter nonlymphoid tissues or to be productively activated in the absence of inflammation.

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Relative cerebral glucose metabolism was examined with positron-emission tomography (PET) as a measure of neuronal activation during performance of the classically conditioned eyeblink response in 12 young adult subjects. Each subject received three sessions: (i) a control session with PET scan in which unpaired presentations of the tone conditioned stimulus and corneal airpuff unconditioned stimulus were administered, (ii) a paired training session to allow associative learning to occur, and (iii) a paired test session with PET scan. Brain regions exhibiting learning-related activation were identified as those areas that showed significant differences in glucose metabolism between the unpaired control condition and well-trained state in the 9 subjects who met the learning criterion. Areas showing significant activation included bilateral sites in the inferior cerebellar cortex/deep nuclei, anterior cerebellar vermis, contralateral cerebellar cortex and pontine tegmentum, ipsilateral inferior thalamus/red nucleus, ipsilateral hippocampal formation, ipsilateral lateral temporal cortex, and bilateral ventral striatum. Among all subjects, including those who did not meet the learning criterion, metabolic changes in ipsilateral cerebellar nuclei, bilateral cerebellar cortex, anterior vermis, contralateral pontine tegmentum, ipsilateral hippocampal formation, and bilateral striatum correlated with degree of learning. The localization to cerebellum and its associated brainstem circuitry is consistent with neurobiological studies in the rabbit model of eyeblink classical conditioning and neuropsychological studies in brain-damaged humans. In addition, these data support a role for the hippocampus in conditioning and suggest that the ventral striatum may also be involved.

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Contains notes taken by Harvard student Lyman Spalding (1775-1821) from lectures on anatomy and surgery delivered by Harvard Professor John Warren (1753-1815) in 1795, as well a section entitled “Medical Observations,” which includes entries on “Vernal Debility,” or diseases occurring in the spring, and lung function. It is unclear if these are Spalding’s own writings or transcriptions from a published work. There is also text transcribed from “Elementa Medicinae,” published in 1780 by Scottish physician John Brown.

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Volume containing notes on the lectures of Henry Cline (1750-1827), a surgeon at St. Thomas's Hospital, London, England, that were kept by American medical student John Collins Warren in 1799 and 1800. The lectures were on topics including blood, blood vessels, absorbents, cellular membranes, and the nerves. There are annotations in pencil in an unknown hand throughout the volume.

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The Crimean operation has served as an occasion for Russia to demonstrate to the entire world the capabilities and the potential of information warfare. Its goal is to use difficult to detect methods to subordinate the elites and societies in other countries by making use of various kinds of secret and overt channels (secret services, diplomacy and the media), psychological impact, and ideological and political sabotage. Russian politicians and journalists have argued that information battles are necessary for “the Russian/Eurasian civilisation” to counteract “informational aggression from the Atlantic civilisation led by the USA”. This argument from the arsenal of applied geopolitics has been used for years. This text is an attempt to provide an interpretation of information warfare with the background of Russian geopolitical theory and practice.

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Mode of access: Internet.

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Mode of access: Internet.

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Mode of access: Internet.

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Mode of access: Internet.