Hierarchical Models in the Brain

This paper describes a general model that subsumes many parametric models for continuous data. The model comprises hidden layers of state-space or dynamic causal models, arranged so that the output of one provides input to another. The ensuing hierarchy furnishes a model for many types of data, of arbitrary complexity. Special cases range from the general linear model for static data to generalised convolution models, with system noise, for nonlinear time-series analysis. Crucially, all of these models can be inverted using exactly the same scheme, namely, dynamic expectation maximization. This means that a single model and optimisation scheme can be used to invert a wide range of models. We present the model and a brief review of its inversion to disclose the relationships among, apparently, diverse generative models of empirical data. We then show that this inversion can be formulated as a simple neural network and may provide a useful metaphor for inference and learning in the brain

Pregnancy-related pelvic girdle pain: an update

A large number of scientists from a wide range of medical and surgical disciplines have reported on the existence and characteristics of the clinical syndrome of pelvic girdle pain during or after pregnancy. This syndrome refers to a musculoskeletal type of persistent pain localised at the anterior and/or posterior aspect of the pelvic ring. The pain may radiate across the hip joint and the thigh bones. The symptoms may begin either during the first trimester of pregnancy, at labour or even during the postpartum period. The physiological processes characterising this clinical entity remain obscure. In this review, the definition and epidemiology, as well as a proposed diagnostic algorithm and treatment options, are presented. Ongoing research is desirable to establish clear management strategies that are based on the pathophysiologic mechanisms responsible for the escalation of the syndrome's symptoms to a fraction of the population of pregnant women

Colonoscopia ou sigmoidoscopia: risco de lesões isoladas no cólon direito Colonoscopy or flexible sigmoidoscopy: risk of isolated right colon lesions

Racional &#151; Atualmente existem dúvidas quanto ao método ideal de rastreio e vigilância para o câncer colorretal. A retossigmoidoscopia é preconizada, já que é barata, eficaz e causa pouco desconforto, mas não pode diagnosticar tumores do cólon proximal. Objetivo - Avaliar quantas lesões encontradas no cólon proximal seriam perdidas caso a colonoscopia só fosse empregada em pacientes com lesões detectadas durante sigmoidoscopia. Casuística e Método - Foram revistas as colonoscopias consecutivas com achado de pólipos ou neoplasia, realizadas no Setor de Endoscopia da Disciplina de Gastroenterologia da Universidade Federal de São Paulo, excluindo pacientes repetidos, operados ou com doença inflamatória intestinal. Resultados - Cento e um exames foram elegíveis, sendo 45 pacientes do sexo masculino. A idade média foi 62 anos (DP &plusmn; 13,7 anos). Cento e oito fragmentos foram enviados separadamente para exame anatomopatológico, sendo 38 com suspeita de neoplasia e 70 pólipos. Ao se considerarem apenas os achados no cólon proximal, observou-se o total de 45 lesões, sendo 23 adenomas, 10 adenocarcinomas, 1 linfoma e 11 lesões benignas. Destas lesões, 28 eram isoladas, sendo 16 adenomas, 7 adenocarcinomas. Conclusão &#151; Observaram-se que 23 pacientes (22,77%) tinham adenoma ou adenocarcinoma apenas no cólon direito, que não seriam diagnosticados se sigmoidoscopia flexível fosse usada isoladamente.<br>Background &#151; Colorectal cancer is an important cause of death in western countries. Screening methods are based on flexible sigmoidoscopy, a cheap, effective, and less painful procedure, but some important lesions on the right colon can be missed. Aim - Evaluate how many important lesions would be missed if colonoscopy indicated only for patients with distal lesions identified during flexible sigmoidoscopy. Material and Methods - All consecutive colonoscopy performed in the Endoscopy Unit of the Gastroenterology Division of Federal University of São Paulo, SP, Brazil, with polyps and cancer suspicious lesions were reviewed. Patients with a second procedure, inflammatory bowel disease or colonic surgery were excluded. Results - We reviewed 101 patients with 38 possible cancer lesions and 70 polyps. The mean age was 62 years (SD 13,7 years) and 45 were male. Forty five lesions were in the right colon, namely 23 adenomas, 10 adenocarcinomas, 1 lymphoma and 11 benign lesion. Among such lesions, 28 were isolated in the right colon (16 adenomas and 7 adenocarcinomas). Conclusion - In our study 23 patients (22,77%) had adenomas or adenocarcinomas isolated in the right colon, that would be missed if flexible sigmoidoscopy was used alone