Discriminatively Trained Latent Ordinal Model for Video Classification

We study the problem of video classification for facial analysis and human action recognition. We propose a novel weakly supervised learning method that models the video as a sequence of automatically mined, discriminative sub-events (eg. onset and offset phase for "smile", running and jumping for "highjump"). The proposed model is inspired by the recent works on Multiple Instance Learning and latent SVM/HCRF -- it extends such frameworks to model the ordinal aspect in the videos, approximately. We obtain consistent improvements over relevant competitive baselines on four challenging and publicly available video based facial analysis datasets for prediction of expression, clinical pain and intent in dyadic conversations and on three challenging human action datasets. We also validate the method with qualitative results and show that they largely support the intuitions behind the method.Comment: Paper accepted in IEEE TPAMI. arXiv admin note: substantial text overlap with arXiv:1604.0150

Classification of postoperative surgical site infections from blood measurements with missing data using recurrent neural networks

Clinical measurements that can be represented as time series constitute an important fraction of the electronic health records and are often both uncertain and incomplete. Recurrent neural networks are a special class of neural networks that are particularly suitable to process time series data but, in their original formulation, cannot explicitly deal with missing data. In this paper, we explore imputation strategies for handling missing values in classifiers based on recurrent neural network (RNN) and apply a recently proposed recurrent architecture, the Gated Recurrent Unit with Decay, specifically designed to handle missing data. We focus on the problem of detecting surgical site infection in patients by analyzing time series of their blood sample measurements and we compare the results obtained with different RNN-based classifiers

Long Term Effects of Chronic Variable Stress Administered during Different Developmental Stages in Mice

A number of studies have suggested that the occurrence of past trauma can increase an individual\u27s chance of developing PTSD from a new traumatic experience later in life. Trauma that occurs during childhood appears to have a particularly strong effect on this risk increase. Furthermore, conditioned fear responses have been shown to incubate over extended periods of time in animal models. To further investigate the role these phenomena play in the development of PTSD, this study exposed juvenile and adult mice to 7 days of chronic variable stress (CVS). One month later, a Pavlovian delay fear conditioning procedure was used to assess fear learning behavior, and anxiety levels were assessed with an Elevated Plus-Maze (EPM). It was hypothesized that mice who experienced CVS exposure as juveniles would show greater long-term levels of anxiety and long-term sensitization to later fear learning than mice who experienced CVS as adults. Furthermore, mice exposed to CVS, regardless of age, were hypothesized to show significantly enhanced anxiety and fear conditioning relative to control mice. Surprisingly, it was found that stress induced sensitization of fear conditioning deteriorated over the 30-day incubation period for both juvenile and adult mice, leading to no differences between groups, including controls, in fear learning behaviors. Adult stressed mice showed significantly greater anxiety levels than adult controls, while juvenile stressed and control mice showed no difference in anxiety. These results suggest possible neurological differences between juvenile and adult mice in regions involved in fear learning, such as the hippocampus, the central nucleus of the amygdale, and the bed nucleus of the stria terminalis. Alternative interpretations of the data are discussed. Despite failing to support the proposed hypotheses, this study suggests that a successful animal model of PTSD should consider the differential dynamics of associative and non-associative fear learning processes. Furthermore, the moderating effects of developmental stages on the effects of chronic stress should also be acknowledged and investigated further