LINFADENITE INFECCIOSA EM SUÍNOS: ETIOLOGIA, EPIDEMIOLOGIA E ASPECTOS EM SAÚDE PÚBLICA

RESUMO A linfadenite infecciosa em suínos gera altos prejuízos com a condenação de carcaças, pela similaridade das lesões causadas pelos agentes causais e de certos micro-organismos, reforçando a necessidade da vigilância sanitária continuada nas afecções de linfonodos em suínos. O crescente isolamento de Mycobacterium sp. e de Rhodococcus equi em pacientes acometidos pela síndrome da imunodeficiência adquirida (Aids) redobrou a preocupação na vigilância da linfadenite na linha de abate, em virtude destes micro-organismos figurarem dentre as principais causas da linfadenite em suínos. O presente artigo revisou os principais aspectos da linfadenite infecciosa em suínos, com ênfase na epidemiologia e reflexos em saúde pública, e a ocorrência de Mycobacterium sp. e R. equi como agentes causais da linfadenite.

Competitive Hebbian learning and the hippocampal place cell system: modeling the interaction of visual and path integration cues

The hippocampus has long been thought essential for implementing a cognitive map of the environment. However, almost 30 years since place cells were found in rodent hippocampal field CA1, it is still unclear how such an allocentric representation arises from an ego-centrically perceived world. By means of a competitive Hebbian learning rule responsible for coding visual and path integration cues, our model is able to explain the diversity of place cell responses observed in a large set of electrophysiological experiments with a single fixed set of parameters. Experiments included changes observed in place fields due to exploration of a new environment, darkness, retrosplenial cortex inactivation, and removal, rotation, and permutation of landmarks. To code for visual cues for each landmark, we defined two perceptual schemas representing landmark bearing and distance information over a linear array of cells. The information conveyed by the perceptual schemas is further processed through a network of adaptive layers which ultimately modulate the resulting activity of our simulated place cells. In path integration terms, our system is able to dynamically remap a bump of activity coding for the displacement of the animal in relation to an environmental anchor. We hypothesize that path integration information is computed in the rodent posterior parietal cortex and conveyed to the hippocampus where, together with visual information, it modulates place cell activity. The resulting network yields a more direct treatment of partial remapping of place fields than other models. In so doing, it makes new predictions regarding the nature of the interaction between visual and path integration cues during new learning and when the system is challenged with environmental changes.

Dissociation of the effects of bilateral lesions of the dorsal hippocampus and parietal cortex on path integration in the rat

Rodents are able to rely on self-motion (idiothetic) cues and navigate toward a reference place by path integration. The authors tested the effects of dorsal hippocampal and parietal lesions in a homing task to dissociate the respective roles of the hippocampus and the parietal cortex in path integration. Hippocampal rats exhibited a strong deficit in learning the basic task. Parietal rats displayed a performance impairment as a function of the complexity of their outward paths when the food was placed at varying locations. These results suggest that the parietal cortex plays a specific role in path integration and in the processing of idiothetic information, whereas the hippocampus is involved in the calibration of space used by the path integration system.

Dissociation of the effects of bilateral lesions of the dorsal hippocampus and parietal cortex on path integration in the rat

Rodents are able to rely on self-motion (idiothetic) cues and navigate toward a reference place by path integration. The authors tested the effects of dorsal hippocampal and parietal lesions in a homing task to dissociate the respective roles of the hippocampus and the parietal cortex in path integration. Hippocampal rats exhibited a strong deficit in learning the basic task. Parietal rats displayed a performance impairment as a function of the complexity of their outward paths when the food was placed at varying locations. These results suggest that the parietal cortex plays a specific role in path integration and in the processing of idiothetic information, whereas the hippocampus is involved in the calibration of space used by the path integration system.

Hycones: a hybrid approach to designing decision support systems

Hycones II is a tool that facilitates the construction of hybrid connectionist expert systems to solve problems in classification. Hycones II provides a hybrid system that integrates frames with three types of neural network: the "combinatorial" neural model (CNM), the "Fuzzy ARTMAP" model, and the "Semantic ART" (SMART) model, a combination of the CNM and Fuzzy ART-MAP. We will compare the ability of these three models to solve diagnostic problems in two medical domains.

HYCONES II: a tool to build hybrid connectionist expert systems

This paper describes HYCONES II--a tool to enable the construction of hybrid connectionist expert systems to solve classification problems. HYCONES II offers to the knowledge engineer a hybrid knowledge base that integrates frames with three different neural network models: the combinatorial neural model--CNM, the Fuzzy ARTMAP and the Semantic ART--SMART models. The latter is a new model, introduced by this paper, based on a combination of the two previous models. The validation section compares the performance of these three neural models to solve diagnostic problems in two medical domains. This paper also presents HYCONES II knowledge representation features, built in the symbolic component of its hybrid knowledge-base, to deal and represent fuzzy medical variables. Finally, the present status and future developments of the project are presented.