Publications

Predicting conversion to psychosis in clinical high risk patients using resting-state functional MRI features
Jolie Mcdonnell
W. Hord
Jenna Reinen
Pablo Polosecki
Irina Rish
Guillermo Cecchi
Recent progress in artificial intelligence provides researchers with a powerful set of machine learning tools for analyzing brain imaging da… (voir plus)ta. In this work, we explore a variety of classification algorithms and functional network features derived from resting-state fMRI data collected from clinical high-risk (prodromal schizophrenia) patients and controls, trying to identify features predictive of conversion to psychosis among a subset of CHR patients. While there are many existing studies suggesting that functional network features can be highly discriminative of schizophrenia when analyzing fMRI of patients suffering from the disease vs controls, few studies attempt to explore a similar approach to actual prediction of future psychosis development ahead of time, in the prodromal stage. Our preliminary results demonstrate the potential of fMRI functional network features to predict the conversion to psychosis in CHR patients. However, given the high variance of our results across different classifiers and subsets of data, a more extensive empirical investigation is required to reach more robust conclusions.
2019-02-16
Medical Imaging 2019: Biomedical Applications in Molecular, Structural, and Functional Imaging (publié)
doi.org
Anytime Tail Averaging
Nicolas Le Roux
Tail averaging consists in averaging the last examples in a stream. Common techniques either have a memory requirement which grows with the … (voir plus)number of samples to average, are not available at every timestep or do not accomodate growing windows. We propose two techniques with a low constant memory cost that perform tail averaging with access to the average at every time step. We also show how one can improve the accuracy of that average at the cost of increased memory consumption.
2019-02-13
ArXiv (prépublication)
arxiv.org
arxiv.org
Distributional reinforcement learning with linear function approximation
Marc Gendron-Bellemare
Nicolas Le Roux
Pablo Samuel Castro
Subhodeep Moitra
Despite many algorithmic advances, our theoretical understanding of practical distributional reinforcement learning methods remains limited.… (voir plus) One exception is Rowland et al. (2018)'s analysis of the C51 algorithm in terms of the Cramer distance, but their results only apply to the tabular setting and ignore C51's use of a softmax to produce normalized distributions. In this paper we adapt the Cramer distance to deal with arbitrary vectors. From it we derive a new distributional algorithm which is fully Cramer-based and can be combined to linear function approximation, with formal guarantees in the context of policy evaluation. In allowing the model's prediction to be any real vector, we lose the probabilistic interpretation behind the method, but otherwise maintain the appealing properties of distributional approaches. To the best of our knowledge, ours is the first proof of convergence of a distributional algorithm combined with function approximation. Perhaps surprisingly, our results provide evidence that Cramer-based distributional methods may perform worse than directly approximating the value function.
2019-02-08
ArXiv (prépublication)
arxiv.org
arxiv.org
Distributional reinforcement learning with linear function approximation
Marc Gendron-Bellemare
Nicolas Le Roux
Pablo Samuel Castro
Subhodeep Moitra
Despite many algorithmic advances, our theoretical understanding of practical distributional reinforcement learning methods remains limited.… (voir plus) One exception is Rowland et al. (2018)'s analysis of the C51 algorithm in terms of the Cramer distance, but their results only apply to the tabular setting and ignore C51's use of a softmax to produce normalized distributions. In this paper we adapt the Cramer distance to deal with arbitrary vectors. From it we derive a new distributional algorithm which is fully Cramer-based and can be combined to linear function approximation, with formal guarantees in the context of policy evaluation. In allowing the model's prediction to be any real vector, we lose the probabilistic interpretation behind the method, but otherwise maintain the appealing properties of distributional approaches. To the best of our knowledge, ours is the first proof of convergence of a distributional algorithm combined with function approximation. Perhaps surprisingly, our results provide evidence that Cramer-based distributional methods may perform worse than directly approximating the value function.
2019-02-08
ArXiv (preprint)
arxiv.org
arxiv.org
Dendritic solutions to the credit assignment problem
Blake Richards
Timothy P. Lillicrap
2019-02-01
Current Opinion in Neurobiology (publié)
doi.org
A Geometric Perspective on Optimal Representations for Reinforcement Learning
Marc Gendron-Bellemare
Will Dabney
Robert Dadashi
Adrien Ali Taiga
Pablo Samuel Castro
Nicolas Le Roux
Dale Eric. Schuurmans
Tor Lattimore
Clare Lyle
We propose a new perspective on representation learning in reinforcement learning based on geometric properties of the space of value functi… (voir plus)ons. We leverage this perspective to provide formal evidence regarding the usefulness of value functions as auxiliary tasks. Our formulation considers adapting the representation to minimize the (linear) approximation of the value function of all stationary policies for a given environment. We show that this optimization reduces to making accurate predictions regarding a special class of value functions which we call adversarial value functions (AVFs). We demonstrate that using value functions as auxiliary tasks corresponds to an expected-error relaxation of our formulation, with AVFs a natural candidate, and identify a close relationship with proto-value functions (Mahadevan, 2005). We highlight characteristics of AVFs and their usefulness as auxiliary tasks in a series of experiments on the four-room domain.
2019-01-31
ArXiv (prépublication)
arxiv.org
arxiv.org
Author Correction: Why rankings of biomedical image analysis competitions should be interpreted with care
Lena Maier-Hein
Matthias Eisenmann
Annika Reinke
Sinan Onogur
Marko Stankovic
Patrick Scholz
Tal Arbel
Hrvoje Bogunovic
Andrew P. Bradley
Aaron Carass
Carolin Feldmann
Alejandro F. Frangi
Peter M. Full
Bram van Ginneken
Allan Hanbury
Katrin Honauer
Michal Kozubek
Bennett Landman
Keno März
Oskar Maier … (voir 18 de plus)
Klaus Maier-Hein
Bjoern Menze
Henning Müller
Peter F. Neher
Wiro Niessen
Nasir Rajpoot
Gregory C. Sharp
Korsuk Sirinukunwattana
Stefanie Speidel
Christian Stock
Danail Stoyanov
Abdel Aziz Taha
Fons van der Sommen
Ching-Wei Wang
Marc-André Weber
Guoyan Zheng
Pierre Jannin
Annette Kopp-Schneider
2019-01-30
Nature Communications (publié)
doi.org
Session-Based Social Recommendation via Dynamic Graph Attention Networks
Weiping Song
Zhiping Xiao
Yifan Wang
Laurent Charlin
Ming Zhang
Jian Tang
Online communities such as Facebook and Twitter are enormously popular and have become an essential part of the daily life of many of their … (voir plus)users. Through these platforms, users can discover and create information that others will then consume. In that context, recommending relevant information to users becomes critical for viability. However, recommendation in online communities is a challenging problem: 1) users' interests are dynamic, and 2) users are influenced by their friends. Moreover, the influencers may be context-dependent. That is, different friends may be relied upon for different topics. Modeling both signals is therefore essential for recommendations. We propose a recommender system for online communities based on a dynamic-graph-attention neural network. We model dynamic user behaviors with a recurrent neural network, and context-dependent social influence with a graph-attention neural network, which dynamically infers the influencers based on users' current interests. The whole model can be efficiently fit on large-scale data. Experimental results on several real-world data sets demonstrate the effectiveness of our proposed approach over several competitive baselines including state-of-the-art models.
2019-01-30
Proceedings of the Twelfth ACM International Conference on Web Search and Data Mining (publié)
doi.org
arxiv.org
What comes next? Extractive summarization by next-sentence prediction
Jingyun Liu
Jackie Cheung
Annie Priyadarshini Louis
Existing approaches to automatic summarization assume that a length limit for the summary is given, and view content selection as an optimiz… (voir plus)ation problem to maximize informativeness and minimize redundancy within this budget. This framework ignores the fact that human-written summaries have rich internal structure which can be exploited to train a summarization system. We present NEXTSUM, a novel approach to summarization based on a model that predicts the next sentence to include in the summary using not only the source article, but also the summary produced so far. We show that such a model successfully captures summary-specific discourse moves, and leads to better content selection performance, in addition to automatically predicting how long the target summary should be. We perform experiments on the New York Times Annotated Corpus of summaries, where NEXTSUM outperforms lead and content-model summarization baselines by significant margins. We also show that the lengths of summaries produced by our system correlates with the lengths of the human-written gold standards.
2019-01-12
ArXiv (prépublication)
arxiv.org
arxiv.org
A Geometric Perspective on Optimal Representations for Reinforcement Learning
Marc Gendron-Bellemare
Will Dabney
Robert Dadashi
Adrien Ali Taiga
Pablo Samuel Castro
Nicolas Le Roux
Dale Schuurmans
Tor Lattimore
Clare Lyle
We propose a new perspective on representation learning in reinforcement learning based on geometric properties of the space of value functi… (voir plus)ons. We leverage this perspective to provide formal evidence regarding the usefulness of value functions as auxiliary tasks. Our formulation considers adapting the representation to minimize the (linear) approximation of the value function of all stationary policies for a given environment. We show that this optimization reduces to making accurate predictions regarding a special class of value functions which we call adversarial value functions (AVFs). We demonstrate that using value functions as auxiliary tasks corresponds to an expected-error relaxation of our formulation, with AVFs a natural candidate, and identify a close relationship with proto-value functions (Mahadevan, 2005). We highlight characteristics of AVFs and their usefulness as auxiliary tasks in a series of experiments on the four-room domain.
arxiv.org
Improving advance medical directives: lessons from Quebec
Louise G. Bernier
Catherine Régis
Policy-makers’ efforts to increase the uptake of advance medical directives (AMDs), and the legal constraints they impose on health profes… (voir plus)sionals, are bringing greater scrutiny to provincial AMD regimes. In 2015, Quebec introduced a new, legally binding form to be filled out for AMDs, which limits individuals’ expression of their wishes to narrow, checklist responses to questions on specific medical interventions. This form-focused regime has other shortcomings: it relies on individuals to self-inform and it does not provide them the opportunity to meaningfully convey their preferences for end-of-life care. A more values-based and collaborative approach provides a better path forward for Quebec and for other provinces.
2019-01-01
(publié)
www.semanticscholar.org
Interpolated Adversarial Training: Achieving Robust Neural Networks without Sacrificing Accuracy
Alex Lamb
Vikas Verma
Juho Kannala
Yoshua Bengio
Adversarial robustness has become a central goal in deep learning, both in theory and practice. However, successful methods to improve adver… (voir plus)sarial robustness (such as adversarial training) greatly hurt generalization performance on the clean data. This could have a major impact on how adversarial robustness affects real world systems (i.e. many may opt to forego robustness if it can improve performance on the clean data). We propose Interpolated Adversarial Training, which employs recently proposed interpolation based training methods in the framework of adversarial training. On CIFAR-10, adversarial training increases clean test error from 5.8% to 16.7%, whereas with our Interpolated adversarial training we retain adversarial robustness while achieving a clean test error of only 6.5%. With our technique, the relative error increase for the robust model is reduced from 187.9% to just 12.1%.
2019-01-01
arXiv.org (prépublication)
dblp.uni-trier.de