1,720,966 research outputs found
Particle Beam Therapy (Hadrontherapy): Basis for interest and Clinical Experience
No full textThe particle or hadron beams deployed in radiotherapy (protons, neutrons and helium, carbon, oxygen and neon ions) have physical and radiobiological characteristics which differ from those of conventional radiotherapy beams (photons) and which offer a number of theoretical advantages over conventional radiotherapy. After briefly describing the properties of hadron beams in comparison to photons, this review discusses the indications for hadrontherapy and analyses accumulated experience on the use of this modality to treat mainly neoplastic lesions, as published by the relatively few hadrontherapy centres operating around the world. The analysis indicates that for selected patients and tumours (particularly uveal melanomas and base of skull/spinal chordomas and chondrosarcomas), hadrontherapy produces greater disease-ti ee survival. The advantages of hadrontherapy are most promisingly realised when used in conjunction with modern patient positioning, radiation delivery and focusing techniques (e.g. on-line imaging, three-dimensional conformal radiotherapy) developed to improve the efficacy of photon therapy. Although the construction and running costs of hadrontherapy units are considerably greater than those of conventional facilities, a comprehensive analysis that considers all the costs, particularly those resulting from the failure of less effective conventional radiotherapy, might indicate that hadrontherapy could be cost effective. En conclusion, the growing interest in this form of treatment seems to be fully justified by the results obtained to date, although more efficacy and dosing studies are required. (C) 1998 Elsevier Science Ltd. All rights reserved
Perceptual and conceptual components in implicit and explicit stem completion
No full textThis study was aimed at investigating functional and neuropsychological dissociations between repetition priming and explicit memory tasks. The explicit and implicit versions of the stem completion task were administered to a group of amnesics and a group of control subjects. In Experiment 1 both the explicit and implicit stem completions were significantly higher when the same presentation modality was used for studying and testing than when a change in modality from studying to testing occurred. Amnesics had normal implicit and deficient explicit completion performance. Experiment 2 revealed an advantage of the semantic over the phonological condition only in the explicit task and only in control subjects. Amnesic patients completed the same percentage of words as normal subjects in the phonological and semantic conditions of the implicit task and in the phonological condition of the explicit task but were deficient in intentionally completing semantically processed words. Possible interpretations of these results are discussed according to theoretical models that distinguish memory tasks along an explicit-implicit dichotomy (multiple memory system theory) or along a perceptual-conceptual dichotomy (transfer-appropriate procedures approach), and alternative theoretical positions are evaluated regarding repetition priming and memory deficits in amnesic patients
Analysis of the memory impairment in a post-encephalitic patient with focal retrograde amnesia
No full textThis study aimed to characterize the qualitative pattern of focal retrograde memory impairment shown by a post-encephalitic patient (AV). AV's memory deficit encompassed autobiographical data, public events and famous people. In a public events questionnaire, she demonstrated a smooth negative temporal gradient with good recollection of events that occurred about 15 years before the disease but poor memory of more recent events. Her visual input lexicon was unimpaired, as demonstrated by normal lexicality judgment for words and normal familiarity judgment for proper names, but she was poor in familiarity judgment for famous faces (prosopagnosia) and in accessing the meaning of words or specific information about people. The cerebral MRI demonstrated widespread abnormal intensity areas encroaching upon the white matter of temporal, parietal and occipital lobes but sparing temporal poles and orbito-frontal cortex
Forgetting from long-term memory in severe closed-head injury patients: effect of retrieval conditions and semantic organization
No full textThis study was aimed at investigating long-term forgetting in chronic survivors of severe closed-head injury (CHI). For this purpose, performance decay passing from a 30-sec- to a 60-min-delay test in four memory procedures (Free Recall of unrelated stimuli, Free Recall of related stimuli. Cued Recall and y/n Recognition) of 20 CHI and 20 normal controls was analyzed. Comparable 30-sec-delay performance in CHI and control patients were obtained by manipulating exposure times to study material during the learning phase. Results demonstrated accelerated forgetting in CHI patients in the Free Recall of the related list only. This finding was particularly evident in CHI patients suffering from a focal temporal lobe lesion. These data are discussed in light of retrieval and encoding deficits characterizing memory disorders in CHI patients
Deficient intentional access to semantic knowledge in patients with severe closed-head injury
No full textPatients after severe closed-head injury (CHI) demonstrate reduced ability to spontaneously utilize semantic memory during word-list memory tests and when requested to answer questions regarding general knowledge. However, they show normal lexical facilitation in both automatic and intentional semantic priming paradigms. The present study was aimed at investigating two alternative hypotheses a) that the deficit in semantic processing after CHI is the result of impaired access to an otherwise normal semantic system or b) that it reflects a loss of knowledge from a deteriorated semantic store. For this purpose, the performance of 15 CHI patients on an automatic Semantic Priming paradigm and on tests of Picture Naming and Semantic Judgment were compared to those of 14 normal controls (NC). Although CHI patients' reaction times were significantly slower than those of NCs, the semantic priming effect was comparable in the two groups. Instead, CHI patients performed significantly worse than NCs in the naming and semantic judgment tasks. These results provide evidence that CHI patients access semantic memory automatically at a normal rate. However, when the task is more demanding in terms of processing requests, then CHI patients' performance becomes defective
Orbital Pseudotumor: Case Report and Literature Review
No full text The term orbital pseudotumor refers to a broad category of non-specific idiopathic inflammations of the orbit. This disease, which may affect any orbital structure, is one of the commonest causes of exophtalmus, occurring with a similar incidence in both sexes. The diagnosis is based on a combination of clinical, radiological and histopathological findings, after careful exclusion of specific systemic and local diseases. Many classification systems have been proposed and a range of therapeutic modalities, including surgery, steroids, immunosuppressive agents, and radiation therapy, have been employed by various authors in heterogeneous series of patients. This slowly proliferating disease, which usually presents with a long clinical history and high variability in clinical manifestations and prognosis, is difficult to manage with any of the available therapeutic options. The difficulties and controversies regarding the diagnostic and therapeutic management of these patients are addressed in an updated review of the literature and exemplified in our case report. </jats:p
Recency effect in anterograde amnesia: evidence for distinct memory stores underlying enhanced retrieval of terminal items in immediate and delayed recall paradigms
No full textThis study was devised to investigate immediate and delayed recency effects in anterograde amnesic patients. For this purpose, a word-list immediate recall paradigm and a modified version of the procedure devised by Baddeley and Hitch [Attention and Performance, Erlbaum, NJ, 1977] for eliciting the recency effect in delayed recall conditions was administered to a sample of amnesic patients and to a group of age-matched healthy subjects. Amnesics disclosed a fully normal recency effect in the immediate recall paradigm and a deficient recency effect in the delayed recall condition. These data, taken together with experimental evidence from a patient affected by a pure form of phonological short-term memory impairment [35], draw a double neuropsychological dissociation suggesting a differential origin for the two kinds of recency effects: a short-term memory output underlying enhanced recall of terminal items in immediate recall paradigms, and an ordinal retrieval strategy applied to long-term memory stored units at the root of the delayed recency effect
Memory performances in young, elderly, and very old healthy individuals versus patients with Alzheimer's disease: evidence for discontinuity between normal and pathological aging
No full textIn this study we compared memory performances of 29 probable patients with AD (17 mildly and 12 moderately demented) with those of 39 healthy young subjects, 36 elderly subjects (matched with the AD group for age and years of schooling), and 19 healthy very old subjects. In most of the memory tasks used in the present study, a progressive decline in performance was observed passing from the Young to the Elderly to the Very Old to the AD group. However, patients with AD were selectively impaired in the backward reproduction of verbal and spatial span sequences and in the semantic encoding of verbal material. These data are consistent with the hypothesis of not only quantitative but also a qualitative discontinuity between the process of normal aging and the dementia syndrome
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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