Competition among multiple memory systems: converging evidence from animal and human brain studies

Research of the neurobiological bases of learning and memory suggest that these processes are not unitary in nature, but rather that relatively independent neural systems appear to mediate different types of memory. Neurobiological studies, for instance, have identified separable cognitive or "declarative" and stimulus-response "habit" memory systems that rely upon the medial temporal lobe (e.g. hippocampus) and basal ganglia (e.g. caudate-putamen), respectively. Evidence indicates that multiple memory systems are activated simultaneously and in parallel in various learning tasks, and recent findings suggest that these systems may interact. One form of interaction between medial temporal lobe and basal ganglia memory systems appears competitive in nature, and has been revealed in non-human animal studies in which damage to a given memory system results in enhanced learning. Recent human neuroimaging research has also provided evidence in favor of competition between memory systems. Thus, converging evidence across species supports the hypothesis of interactive multiple memory systems in the mammalian brain. Potential neurobiological mechanisms mediating such interactions include direct anatomical projections between the medial temporal lobe and basal ganglia, indirect neuromodulatory influences of other brain structures (e.g. basolateral amygdala) and activity of neocortical brain regions involved in top-down response selection.     

Rates of species loss from Amazonian forest fragments

In the face of worldwide habitat fragmentation, managers need to devise a time frame for action. We ask how fast do understory bird species disappear from experimentally isolated plots in the Biological Dynamics of Forest Fragments Project, central Amazon, Brazil. Our data consist of mist-net records obtained over a period of 13 years in 11 sites of 1, 10, and 100 hectares. The numbers of captures per species per unit time, analyzed under different simplifying assumptions, reveal a set of species-loss curves. From those declining numbers, we derive a scaling rule for the time it takes to lose half the species in a fragment as a function of its area. A 10-fold decrease in the rate of species loss requires a 1,000-fold increase in area. Fragments of 100 hectares lose one half of their species in <15 years, too short a time for implementing conservation measures.     

Mesiodens--diagnosis and management of a common supernumerary tooth

Mesiodentes are the most common supernumerary teeth, occurring in 0.15% to 1.9% of the population. Given this high frequency, the general dentist should be knowledgeable about the signs and symptoms of mesiodentes and appropriate treatment. The cause of mesiodentes is not fully understood, although proliferation of the dental lamina and genetic factors have been implicated. Mesiodentes can cause delayed or ectopic eruption of the permanent incisors, which can further alter occlusion and appearance. It is therefore important for the clinician to diagnose a mesiodens early in development to allow for optimal yet minimal treatment. Treatment options may include surgical extraction of the mesiodens. If the permanent teeth do not erupt in a reasonable period after the extraction, surgical exposure and orthodontic treatment may be required to ensure eruption and proper alignment of the teeth. In some instances, fixed orthodontic therapy is also required to create sufficient arch space before eruption and alignment of the incisor(s). Early diagnosis allows the most appropriate treatment, often reducing the extent of surgery, orthodontic treatment and possible complications. This paper outlines the causes and modes of presentation of mesiodentes, and presents guidelines for diagnosis and management of nonsyndromic mesiodentes.     

Using aviation safety measures to enhance patient outcomes

Recent media reports have put a spotlight on the increasing number of medical errors occurring in US health care institutions. In contrast to health care's increasing error rate, the aviation industry is experiencing a decreasing error rate. Could the safety techniques used in the aviation industry be applied to health care? This article explores that question. The dynamics of the surgical suite are not unlike those of the cockpit of an airplane; therefore, perioperative services was selected to pilot test the aviation model of safety training.     

Ureteroscopy for the treatment of urolithiasis in children

PURPOSE: Ureteroscopy for treating urolithiasis in prepubertal children has become more common with the advent of smaller instruments. We reviewed our experience with ureteroscopy for urolithiasis in this cohort of patients as well as the literature using this treatment modality in children. MATERIALS AND METHODS: Between 1994 and 2000 we performed 27 ureteroscopic stone extractions in 25 children. Ureteroscopy was done in a manner similar to that in adults. Ureteral dilation was performed when necessary to access the ureter. A stent was placed postoperatively if there was significant ureteral trauma. RESULTS: Of the 25 children 13 were male and 12 were female. Average age was 9.2 years (range 3 to 14). Stones were 2 to 12 mm. in greatest diameter (average 6). Of the 27 procedures the ureteral orifice was dilated before stone treatment in 15 (56%), while in 19 (70%) a stent was placed afterward. No intraoperative and 2 postoperative complications were identified. Overall 92% of the children were rendered stone-free after 1 procedure and 100% were stone-free after 2. CONCLUSIONS: Ureteroscopy for urolithiasis in prepubertal children is safe and effective. Routine ureteral dilation and ureteral stent placement are not always necessary in these patients.     

Effects of ZD6169 and ZD0947, 2 potassium adenosine triphosphate channel openers,on bladder function of spinalized rats

PURPOSE: The use of K+ channel openers is emerging as an attractive possibility for treating bladder overactivity. We tested the efficacy of the 2 adenosine triphosphate dependent K channel openers ZD6169 and ZD0947 on detrusor hyperreflexia after spinal cord injury in rats. MATERIALS AND METHODS: Included in this study were 72 adult Sprague-Dawley rats. Six animals served as normal controls, while 66 underwent spinal cord transection at the 10th thoracic vertebra. Two weeks after spinal cord injury 6 animals underwent filling cystometrography to confirm detrusor hyperreflexia, while another 12 served as control paraplegics. For each drug 24 animals were used and divided into 2 equal groups of 12. Group 1 received the drug in a dose of 3 mg./kg. daily, while group 2 received a dose of 0.3 mg./kg. daily. Each control paraplegic and treatment group was further subdivided into 2 subgroups of 6 rats. In subgroup 1 filling cystometrography was done 3 weeks after spinal cord injury, while in subgroup 2 it was done 4 weeks after spinal cord injury. RESULTS: Three weeks after spinal cord injury detrusor hyperreflexia developed in all control paraplegic animals with a mean bladder capacity plus or minus standard deviation of 0.7 +/- 0.2 ml. and a mean voiding pressure of 59 +/- 14.2 cm. water. Detrusor hyperreflexia resolved in 66% of the animals that received ZD6169 for 1 week at either dose. For example, mean bladder capacity was 2.5 +/- 1.8 versus 1.8 +/- 1.2 ml. and mean voiding pressure was 42.1 +/- 15.9 versus 43.2 +/- 21.4 cm. water in animals that received 3 versus 0.3 mg./kg. daily, respectively. All animals that received a dose of 3 mg./kg. ZD0947 daily for 1 week showed no detrusor hyperreflexia with a mean bladder capacity of 2.7 +/- 1.8 ml. and mean voiding pressure of 34 +/- 8.5 cm. water, while at 0.3 mg./kg. daily 83% showed no detrusor hyperreflexia with a mean bladder capacity of 2.5 +/- 2.0 ml. and a mean voiding pressure of 41.5 +/- 13.8 cm. water. Each drug produced better urodynamic results when given for 2 weeks. CONCLUSIONS: ZD6169 and ZD0947 are effective treatment for detrusor hyperreflexia after spinal cord injury and they may provide alternative treatment options for overactive bladder. Each drug has time and dose dependent response effects that reflect their wide range of efficacy. However, ZD0947 shows an efficacy profile that is relatively superior to that of ZD6169.     

Methods for Semi-automated Indexing for High Precision Information Retrieval

Objective. To evaluate a new system, ISAID (Internet-based Semi-automated Indexing of Documents), and to generate textbook indexes that are more detailed and more useful to readers.Design. Pilot evaluation: simple, nonrandomized trial comparing ISAID with manual indexing methods. Methods evaluation: randomized, cross-over trial comparing three versions of ISAID and usability survey.Participants. Pilot evaluation: two physicians. Methods evaluation: twelve physicians, each of whom used three different versions of the system for a total of 36 indexing sessions.Measurements. Total index term tuples generated per document per minute (TPM), with and without adjustment for concordance with other subjects; inter-indexer consistency; ratings of the usability of the ISAID indexing system.Results. Compared with manual methods, ISAID decreased indexing times greatly. Using three versions of ISAID, inter-indexer consistency ranged from 15% to 65% with a mean of 41%, 31%, and 40% for each of three documents. Subjects using the full version of ISAID were faster (average TPM: 5.6) and had higher rates of concordant index generation. There were substantial learning effects, despite our use of a training/run-in phase. Subjects using the full version of ISAID were much faster by the third indexing session (average TPM: 9.1). There was a statistically significant increase in three-subject concordant indexing rate using the full version of ISAID during the second indexing session (p < 0.05).Summary. Users of the ISAID indexing system create complex, precise, and accurate indexing for full-text documents much faster than users of manual methods. Furthermore, the natural language processing methods that ISAID uses to suggest indexes contributes substantially to increased indexing speed and accuracy.The number of textbooks related to patient care and basic science is already large and continues to grow. In areas of health care with rapidly evolving or intricate management strategies, textbooks constitute a critical resource for health providers. In 1991, Forsythe and colleagues observed clinicians on rounds and in clinics, recording 454 clinical questions that arose and the ultimate sources of answers to these queries.¹ The clinicians obtained answers to many questions by consulting multiple information sources, most often the patient’s medical chart or records or the patient himself. Answering a quarter of the questions, however, required consulting medical library materials. Of these, the answers to more than half were found in a textbook and the remainder in medical journals. In another study, internists’ self-reported use of various information sources roughly matched these figures.² During outpatient treatment of AIDS patients, five textbooks, in conjunction with a system for searching medical journals, provided answers to approximately 75% of clinicians’ questions.³However, the use of textbooks is frequently neither straightforward nor expedient. Searching a textbook consumes on average six minutes of time that could be used for other clinical care tasks.⁴ Faced with an urgent information need, clinicians often must rely on manual inspection of a table of contents or alphabetized keyword index to guide their search. Although formal evaluations of such indexes are lacking, in one study only 30% of internists felt that textbooks are “adequately indexed for rapid information retrieval.”² Tables of content most commonly list only one or two levels of section headings, each indexed by the page number on which the section begins. Alphabetized keyword indexes, like those commonly found at the end of most textbooks, may cross-reference two or more words that occur in the textbook and therefore are usually more precise. However, like tables of content, most of these indexes also direct the reader only to whole pages in the textbook; readers are still left with the time-consuming task of finding specific answers to their questions in the text of those pages.Many textbooks have recently become available in electronic format (e.g., on CD-ROM). Some of these textbooks can now be searched by locating terms that occur in the text, either alone or in some predefined proximity to each other. However, this type of indexing alone is unlikely to improved textbook search precision. Hersh found the precision of information retrieval from one medical textbook using such term search methods to be an abysmal 19%.⁵ In addition, the organization of some electronic medical textbooks is such that low cognitive load tasks (e.g., visual scanning) cannot be performed as easily as with printed versions, even with key term highlighting.⁶Indexes that would allow clinicians, researchers, and patients to retrieve the information they need from these sources rapidly and with greater precision must contain more knowledge than merely the location of the beginning of textbook sections or the numbers of pages on which one or two concepts are discussed. Entries in these indexes must mirror the questions that drive readers to use the textbook to seek knowledge. Furthermore, these indexes must point the reader to more specific locations in the text. For example, consider a resident physician with the specific question “What is the appropriate duration of therapy for the treatment of a patient with Pseudomonas pneumonia using aminoglycosides?” A traditional alphabetized keyword index might contain an entry for “pneumonia” and “therapy” that points to several different pages in a textbook, only a minority of which contain discussions of the length of treatment of pneumonia caused by Pseudomonas species. A superior index would allow residents first to find their exact question in the index and then to find the specific portions of a textbook that contain answers.Both the creation and the use of such detailed and specific indexes present several challenges. First, they are potentially much larger than traditional keyword indexes, because they must include entries for large numbers of different and specific, complex questions readers have, and the specific locations of answers to these questions. Indeed, for many textbooks, such indexes may be so large that they themselves require a system for navigating to a desired question in the index to be of any practical use. Second, the amount of labor required to generate such indexes manually is likely to be very large, because more extensive coordination of indexed terms and more specific reference back into the text are required. Finally, the nature of such detailed, query-based indexes requires that indexers have significant domain-specific knowledge, particularly an understanding of the proper and specific relation between index terms and the ability to recognize index terms in the text that are implied, but not stated.We have developed ELBook, a computer-based system for retrieving fine-grained (i.e., highly specific) information from text documents.⁷ ELBook requires that domain experts make explicit as indexes some of the knowledge contained in the text of documents. However, unlike the pioneering Hepatitis Knowledge-Base,⁸ ELBook does not require indexers to provide a representation of all the knowledge contained in its documents. Query and concept models constrain the space of possible ELBook indexes and queries. Thus, the design of ELBook builds on the attempts by Hersh, Purcell,⁹ and others to incorporate more domain-specific knowledge into full-text IR systems (Table 1Table 1 Full-text Information Retrieval Systems and Selected Characteristics of Their Indexing MethodsEnthusiasm for the retrieval capabilities of ELBook has consistently been tempered, however, by the realization that generating indexes for ELBook without computer-based support is extremely time-consuming.¹⁰ Furthermore, to evaluate the performance of ELBook on any test collection, we require a substantial amount of such precise indexing. If indexes of this type cannot be generated with sufficient accuracy and in an acceptably efficient manner, increases in search precision or recall using these indexes would be moot. Thus, we set out to develop a computer-based system that could provide automated support for indexing full-text documents for use in ELBook.Several researchers have attempted to automate some or all of the process of generating indexes for various types of full-text documents. Investigators at the National Library of Medicine (NLM) have described both semi-automated¹¹ and fully automated¹² indexing systems designed for journal publications. MedLEE, a natural language understanding system, can extract concepts from clinical notes and reports with reasonable accuracy that can then be used as indexes, although modeling domain knowledge for specific applications remains a bottleneck.^13–16 Furthermore, NLP systems like MedLEE typically do not provide support for interactive document indexing; such interaction could improve the accuracy of index generation through human review.This article evaluates ISAID (Internet-based Semi-automated Indexing of Documents), a computer-based system to generate textbook indexes that are more detailed and, hopefully, more useful to readers. This system requires domain-dependent query and concept models as well as a domain-independent document model to provide some of the knowledge required to create such complex indexes. ISAID requires that a domain expert first describe a set of questions, or generic queries, to be used as templates for indexes. Collectively, these questions constitute the query model. The concept model that ISAID uses for the medical domain is largely based on the Unified Medical Language System semantic network. The document model is based on the explicit and implicit structure of Hypertext Markup Language (HTML) documents. ISAID uses a modified vector-space model to help propose candidate indexes. We performed limited comparisons of the ability of ISAID users to generate indexes versus a manual indexing system, and then proceeded to evaluate the contributions of the document and vector-space models to the indexing process. We examined the consistency and speed of indexers using ISAID as a necessary first step towards the evaluation of ELBook.