Comparing brain-like representations learned by vanilla, residual, and recurrent CNN architectures

Though it has been hypothesized that state-of-the art residual networks approximate the recurrent visual system, it is yet to be seen if the representations learned by these biologically inspired CNNs actually have closer representations to neural data. It is likely that CNNs and DNNs that are most functionally similar to the brain will contain mechanisms that are most like those used by the brain. In this thesis, we investigate how different CNN architectures approximate the representations learned through the ventral-object recognition and processing-stream of the brain. We specifically evaluate how recent approximations of biological neural recurrence-such as residual connections, dense residual connections, and a biologically-inspired implemen- tation of recurrence-affect the representations learned by each CNN. We first investigate the representations learned by layers throughout a few state-of-the-art CNNs-VGG-19 (vanilla CNN), ResNet-152 (CNN with residual connections), and DenseNet-161 (CNN with dense connections). To control for differences in model depth, we then extend this analysis to the CORnet family of biologically-inspired CNN models with matching high-level architectures. The CORnet family has three models: a vanilla CNN (CORnet-Z), a CNN with biologically-valid recurrent dynamics (CORnet-R), and a CNN with both recurrent and residual connections (CORnet-S). We compare the representations of these six models to functionally aligned (with hyperalignment) fMRI brain data acquired during a naturalistic visual task. We take two approaches to comparing these CNN and brain representations. We first use forward encoding, a predictive approach that uses CNN features to predict neural responses across the whole brain. We next use representational similarity analysis (RSA) and centered kernel alignment (CKA) to measure the similarities in representation within CNN layers and specific brain ROIs. We show that, compared to vanilla CNNs, CNNs with residual and recurrent connections exhibit representations that are even more similar to those learned by the human ventral visual stream. We also achieve state-of-the-art forward encoding and RSA performance with the residual and recurrent CNN models

Out-of-hours primary care. Implications of organisation on costs

BACKGROUND: To perform out-of-hours primary care, Dutch general practitioners (GPs) have organised themselves in large-scale GP cooperatives. Roughly, two models of out-of-hours care can be distinguished; GP cooperatives working separate from the hospital emergency department (ED) and GP cooperatives integrated with the hospital ED. Research has shown differences in care utilisation between these two models; a significant shift in the integrated model from utilisation of ED care to primary care. These differences may have implications on costs, however, until now this has not been investigated. This study was performed to provide insight in costs of these two different models of out-of-hours care. METHODS: Annual reports of two GP cooperatives (one separate from and one integrated with a hospital emergency department) in 2003 were analysed on costs and use of out-of-hours care. Costs were calculated per capita. Comparisons were made between the two cooperatives. In addition, a comparison was made between the costs of the hospital ED of the integrated model before and after the set up of the GP cooperative were analysed. RESULTS: Costs per capita of the GP cooperative in the integrated model were slightly higher than in the separate model (ε 11.47 and ε 10.54 respectively). Differences were mainly caused by personnel and other costs, including transportation, interest, cleaning, computers and overhead. Despite a significant reduction in patients utilising ED care as a result of the introduction of the GP cooperative integrated within the ED, the costs of the ED remained the same. CONCLUSION: The study results show that the costs of primary care appear to be more dependent on the size of the population the cooperative covers than on the way the GP cooperative is organised, i.e. separated versus integrated. In addition, despite the substantial reduction of patients, locating the GP cooperative at the same site as the ED was found to have little effect on costs of the ED. Sharing more facilities and personnel between the ED and the GP cooperative may improve cost-efficiency

Reverse engineering and rapid prototyping in intervertebral disc tissue engineering

Intervertebral disc (IVD) degeneration disease (IDD) is considered the main cause for low back pain (LBP), which has a world socioeconomic burden of 70 billion euros a year. Tissue Engineering (TE) is an exponentially growing area due to its potential of finding patient-specific treatments in terms of immunological compatibility by using the patient’s own cells. Though, it is possible to increase TE patient-specificity by combining other technologies such as Reverse Engineering (RE) and Rapid Prototyping (RP). In this sense, it is possible to prepare a biodegradable scaffold that is both immunological and structurally compatible. This strategy has the potential to significantly increase implant integration and decrease immunological rejection, allowing the scaffold to be progressively replaced with newly synthesised tissue to ultimately regenerate the IVD into a fully functional anatomical motion segment. Herein is reported a preliminary proof-of-concept for that strategy using rabbit IVD’s cells as well as morphology and structure. In this sense, the annulus fibrosus (AF) structure was replicated by RE and RP into a polycaprolactone scaffold, and the cells were encapsulated in methacrylated gellan gum (GG-MA) hydrogel as a nucleus pulposus (NP) substitute. The AF scaffold’s cytotoxicity, mechanical behaviour, porosity and superficial morphology were also analysed. It was observed a significant level of biocompatibility from the AF replica and a similar porosity in relation with the native IVD. Cell adhesion, proliferation and viability were assessed until 21 days of culture in GG-MA. The metabolic activity was higher in the NP cells than in the fibroblast cell line, both cultured in GG-MA. In the future, this novel strategy is envisaged to treat IDD, and remove LBP, by fully regenerating the intervertebral disc.A degeneração do disco intervertebral é considerada a maior causa de dor lombar, que por sua vez tem um impacto socioeconómico mundial na ordem dos 70 mil milhões de euros por ano. A Engenharia de Tecidos é uma área de investigação que está a crescer exponencialmente e que tem o potencial de desenvolver novos tratamentos, livres de rejeição imunológica, uma vez que são utilizadas células do próprio paciente. No entanto, é possível aumentar esse potencial de compatibilidade com o paciente combinando Engenharia Reversa com Prototipagem Rápida. Com isto visa-se o desenvolvimento de uma estrutura biodegradável e compatível tanto imunologicamente com estruturalmente, que vai sendo progressivamente substituída por novo tecido até se alcançar uma regeneração definitiva do disco intervertebral. A prova-de-conceito preliminar desta estratégia terapêutica é reportada neste estudo através da utilização tanto de células, como a própria estrutura e morfologia, do disco intervertebral de coelho. A estrutura do anel fibroso foi replicada por Engenharia Reversa e Prototipagem Rápida em policaprolactona, enquanto que para servir como substituto do núcleo pulposo foram encapsuladas células num hidrogel de goma gelana metacrilada. A citotoxicidade, comportamento mecânico, morfologia superficial e porosidade da réplica do anel fibroso foram analisadas. Verificou-se que a porosidade é similar ao disco nativo e que o nível de biocompatibilidade está acima de 80%. As imagens de miscroscopia mostraram que as várias camadas da estrutura apresentam uma boa ligação após a solidificação do polímero. A adesão, proliferação e viabilidade celular na goma gelana metacrilada foram analisadas até 21 dias de cultura. Observou-se uma maior actividade metabólica nas células do núcleo pulposo do que na linha celular de fibroblastos, ambas encapsuladas em goma gelana metacrilada. Como trabalho futuro, pretende-se utilizar esta estratégia para tratar casos de degeneração do disco de uma forma efetiva em que o resultado final, após absorção da estrutura, é um disco intervertebral nativo biomecanicamente funcional

Hartrevalidatie : over het bepalen en voorspellen van herstel

Jaarlijks worden in Nederland ongeveer 26.000 patienten opgenomen in een ziekenhuis wegens een hartinfart, of voor het ondergaan van een hartoperatie. Een derde van deze patienten volgt een hartrevalidatieprogramma. Ret gaat hierbij om poliklinische hartrevalidatie. Weliswaar wordt in bijna aile (Nederlandse) ziekenhuizen tijdens de opname van hartpatienten aandacht besteed aan actieve mobilisatie, reactivering en/of training van de normale dagelijkse activiteiten, maar deze vroege klinische revalidatie-activiteiten worden gerekend tot de standaardzorg van het ziekenhuis voor alle patienten. Daarnaast bestaan echter mogelijkheden om na de klinische fase deel te nemen aan een afzonderlijk programma, dat in Nederland doorgaans poliklinisch plaatsvindt in speciale hartrevalidatiecentra. Dit hoek beperkt zich tot de poliklinische hartrevalidatie, omdat dit een extra interventie is, die iets toevoegt aan de standaardzorg en niet aan alle patienten wordt aangeboden. Naar het oordeel van de Nederlandse Hartstichting komen in beginsel aile hartpatienten voor hartrevalidatie in aanmerking. Ret feit dat zowel binnen als buiten Nederland grate aantallen patienten door behandelend artsen worden doorverwezen naar hartrevalidatiecentra, wettigt het vermoeden dat ook bij vele behandelend artsen de verwachting leeft dat hartrevalidatie herstel bevordert.Many studies on cardiac rehabilitation have preceded the one described in this thesis. However, they have not yet led to the scientific recognition of the value of cardiac rehabilitation. A review of the literature forces us to draw the conclusion that cardiac rehabilitation has reached an impasse. Cardiac rehabilitation programmes have largely been developed on the basis of clinical practise. The programmes therefore differ in nature, form and content and consequently are almost impossible to compare. This situation makes it difficult to draw scientific conclusions on the value of cardia