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Elements of neural networks, both biological and artificial, can be described by their selectivity for specific cognitive features. Understanding these features is important for understanding the inner workings of neural networks. For a living system, such as a neuron, whose response to a stimulus is unknown and not differentiable, the only way to reveal these features is through a feedback loop that exposes it to a large set of different stimuli. The properties of these stimuli should be varied iteratively in order to maximize the neuronal response. To utilize this feedback loop for a biological neural network, it is important to run it quickly and efficiently in order to reach the stimuli that maximizes certain neurons' activation with the least number of iterations possible. Here we present a framework with an efficient design for such a loop. We successfully tested it on an artificial spiking neural network (SNN), which is a model that simulates the asynchronous spiking activity of neurons in living brains. Our optimization method for activation maximization is based on the low-rank Tensor Train decomposition of the discrete activation function. The optimization space is the latent parameter space of images generated by SN-GAN or VQ-VAE generative models. To our knowledge, this is the first time that effective AM has been applied to SNNs. We track changes in the optimal stimuli for artificial neurons during training and show that highly selective neurons can form already in the early epochs of training and in the early layers of a convolutional spiking network. This formation of refined optimal stimuli is associated with an increase in classification accuracy. Some neurons, especially in the deeper layers, may gradually change the concepts they are selective for during learning, potentially explaining their importance for model performance.

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神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)(Neural Networks)是(shi)世界上(shang)三個(ge)最古(gu)老(lao)的(de)(de)神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)建(jian)模(mo)學(xue)(xue)會(hui)的(de)(de)檔案期刊:國際神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)學(xue)(xue)會(hui)(INNS)、歐洲神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)學(xue)(xue)會(hui)(ENNS)和(he)(he)(he)(he)(he)(he)(he)日本神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)學(xue)(xue)會(hui)(JNNS)。神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)提供了(le)一(yi)個(ge)論(lun)(lun)壇,以發(fa)(fa)展和(he)(he)(he)(he)(he)(he)(he)培育一(yi)個(ge)國際社(she)會(hui)的(de)(de)學(xue)(xue)者和(he)(he)(he)(he)(he)(he)(he)實踐者感興(xing)趣的(de)(de)所有方面(mian)的(de)(de)神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)和(he)(he)(he)(he)(he)(he)(he)相關(guan)方法的(de)(de)計(ji)(ji)算智能。神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)歡迎高質量論(lun)(lun)文(wen)的(de)(de)提交,有助于(yu)全面(mian)的(de)(de)神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)研究,從行為和(he)(he)(he)(he)(he)(he)(he)大腦建(jian)模(mo),學(xue)(xue)習算法,通過數(shu)學(xue)(xue)和(he)(he)(he)(he)(he)(he)(he)計(ji)(ji)算分析(xi),系統(tong)的(de)(de)工(gong)程(cheng)和(he)(he)(he)(he)(he)(he)(he)技術應用(yong),大量使用(yong)神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)的(de)(de)概念和(he)(he)(he)(he)(he)(he)(he)技術。這一(yi)獨特而廣泛(fan)的(de)(de)范圍促(cu)進了(le)生(sheng)物(wu)和(he)(he)(he)(he)(he)(he)(he)技術研究之間的(de)(de)思想交流,并(bing)有助于(yu)促(cu)進對(dui)生(sheng)物(wu)啟發(fa)(fa)的(de)(de)計(ji)(ji)算智能感興(xing)趣的(de)(de)跨(kua)學(xue)(xue)科社(she)區的(de)(de)發(fa)(fa)展。因此,神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)網(wang)絡(luo)(luo)(luo)(luo)(luo)(luo)編委會(hui)代表的(de)(de)專家(jia)領域包括心(xin)理學(xue)(xue),神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)生(sheng)物(wu)學(xue)(xue),計(ji)(ji)算機科學(xue)(xue),工(gong)程(cheng),數(shu)學(xue)(xue),物(wu)理。該雜志(zhi)發(fa)(fa)表文(wen)章(zhang)、信(xin)件(jian)和(he)(he)(he)(he)(he)(he)(he)評論(lun)(lun)以及給編輯的(de)(de)信(xin)件(jian)、社(she)論(lun)(lun)、時(shi)事、軟件(jian)調(diao)查和(he)(he)(he)(he)(he)(he)(he)專利信(xin)息(xi)。文(wen)章(zhang)發(fa)(fa)表在五個(ge)部分之一(yi):認知科學(xue)(xue),神(shen)(shen)經(jing)(jing)(jing)(jing)(jing)科學(xue)(xue),學(xue)(xue)習系統(tong),數(shu)學(xue)(xue)和(he)(he)(he)(he)(he)(he)(he)計(ji)(ji)算分析(xi)、工(gong)程(cheng)和(he)(he)(he)(he)(he)(he)(he)應用(yong)。 官網(wang)地址:

Recently, graph neural networks have been gaining a lot of attention to simulate dynamical systems due to their inductive nature leading to zero-shot generalizability. Similarly, physics-informed inductive biases in deep-learning frameworks have been shown to give superior performance in learning the dynamics of physical systems. There is a growing volume of literature that attempts to combine these two approaches. Here, we evaluate the performance of thirteen different graph neural networks, namely, Hamiltonian and Lagrangian graph neural networks, graph neural ODE, and their variants with explicit constraints and different architectures. We briefly explain the theoretical formulation highlighting the similarities and differences in the inductive biases and graph architecture of these systems. We evaluate these models on spring, pendulum, gravitational, and 3D deformable solid systems to compare the performance in terms of rollout error, conserved quantities such as energy and momentum, and generalizability to unseen system sizes. Our study demonstrates that GNNs with additional inductive biases, such as explicit constraints and decoupling of kinetic and potential energies, exhibit significantly enhanced performance. Further, all the physics-informed GNNs exhibit zero-shot generalizability to system sizes an order of magnitude larger than the training system, thus providing a promising route to simulate large-scale realistic systems.

Deep neural network based recommendation systems have achieved great success as information filtering techniques in recent years. However, since model training from scratch requires sufficient data, deep learning-based recommendation methods still face the bottlenecks of insufficient data and computational inefficiency. Meta-learning, as an emerging paradigm that learns to improve the learning efficiency and generalization ability of algorithms, has shown its strength in tackling the data sparsity issue. Recently, a growing number of studies on deep meta-learning based recommenddation systems have emerged for improving the performance under recommendation scenarios where available data is limited, e.g. user cold-start and item cold-start. Therefore, this survey provides a timely and comprehensive overview of current deep meta-learning based recommendation methods. Specifically, we propose a taxonomy to discuss existing methods according to recommendation scenarios, meta-learning techniques, and meta-knowledge representations, which could provide the design space for meta-learning based recommendation methods. For each recommendation scenario, we further discuss technical details about how existing methods apply meta-learning to improve the generalization ability of recommendation models. Finally, we also point out several limitations in current research and highlight some promising directions for future research in this area.

We hypothesize that due to the greedy nature of learning in multi-modal deep neural networks, these models tend to rely on just one modality while under-fitting the other modalities. Such behavior is counter-intuitive and hurts the models' generalization, as we observe empirically. To estimate the model's dependence on each modality, we compute the gain on the accuracy when the model has access to it in addition to another modality. We refer to this gain as the conditional utilization rate. In the experiments, we consistently observe an imbalance in conditional utilization rates between modalities, across multiple tasks and architectures. Since conditional utilization rate cannot be computed efficiently during training, we introduce a proxy for it based on the pace at which the model learns from each modality, which we refer to as the conditional learning speed. We propose an algorithm to balance the conditional learning speeds between modalities during training and demonstrate that it indeed addresses the issue of greedy learning. The proposed algorithm improves the model's generalization on three datasets: Colored MNIST, Princeton ModelNet40, and NVIDIA Dynamic Hand Gesture.

What is learned by sophisticated neural network agents such as AlphaZero? This question is of both scientific and practical interest. If the representations of strong neural networks bear no resemblance to human concepts, our ability to understand faithful explanations of their decisions will be restricted, ultimately limiting what we can achieve with neural network interpretability. In this work we provide evidence that human knowledge is acquired by the AlphaZero neural network as it trains on the game of chess. By probing for a broad range of human chess concepts we show when and where these concepts are represented in the AlphaZero network. We also provide a behavioural analysis focusing on opening play, including qualitative analysis from chess Grandmaster Vladimir Kramnik. Finally, we carry out a preliminary investigation looking at the low-level details of AlphaZero's representations, and make the resulting behavioural and representational analyses available online.

Artificial neural networks thrive in solving the classification problem for a particular rigid task, acquiring knowledge through generalized learning behaviour from a distinct training phase. The resulting network resembles a static entity of knowledge, with endeavours to extend this knowledge without targeting the original task resulting in a catastrophic forgetting. Continual learning shifts this paradigm towards networks that can continually accumulate knowledge over different tasks without the need to retrain from scratch. We focus on task incremental classification, where tasks arrive sequentially and are delineated by clear boundaries. Our main contributions concern 1) a taxonomy and extensive overview of the state-of-the-art, 2) a novel framework to continually determine the stability-plasticity trade-off of the continual learner, 3) a comprehensive experimental comparison of 11 state-of-the-art continual learning methods and 4 baselines. We empirically scrutinize method strengths and weaknesses on three benchmarks, considering Tiny Imagenet and large-scale unbalanced iNaturalist and a sequence of recognition datasets. We study the influence of model capacity, weight decay and dropout regularization, and the order in which the tasks are presented, and qualitatively compare methods in terms of required memory, computation time, and storage.

This paper does not describe a working system. Instead, it presents a single idea about representation which allows advances made by several different groups to be combined into an imaginary system called GLOM. The advances include transformers, neural fields, contrastive representation learning, distillation and capsules. GLOM answers the question: How can a neural network with a fixed architecture parse an image into a part-whole hierarchy which has a different structure for each image? The idea is simply to use islands of identical vectors to represent the nodes in the parse tree. If GLOM can be made to work, it should significantly improve the interpretability of the representations produced by transformer-like systems when applied to vision or language

The growing energy and performance costs of deep learning have driven the community to reduce the size of neural networks by selectively pruning components. Similarly to their biological counterparts, sparse networks generalize just as well, if not better than, the original dense networks. Sparsity can reduce the memory footprint of regular networks to fit mobile devices, as well as shorten training time for ever growing networks. In this paper, we survey prior work on sparsity in deep learning and provide an extensive tutorial of sparsification for both inference and training. We describe approaches to remove and add elements of neural networks, different training strategies to achieve model sparsity, and mechanisms to exploit sparsity in practice. Our work distills ideas from more than 300 research papers and provides guidance to practitioners who wish to utilize sparsity today, as well as to researchers whose goal is to push the frontier forward. We include the necessary background on mathematical methods in sparsification, describe phenomena such as early structure adaptation, the intricate relations between sparsity and the training process, and show techniques for achieving acceleration on real hardware. We also define a metric of pruned parameter efficiency that could serve as a baseline for comparison of different sparse networks. We close by speculating on how sparsity can improve future workloads and outline major open problems in the field.

Graph representation learning for hypergraphs can be used to extract patterns among higher-order interactions that are critically important in many real world problems. Current approaches designed for hypergraphs, however, are unable to handle different types of hypergraphs and are typically not generic for various learning tasks. Indeed, models that can predict variable-sized heterogeneous hyperedges have not been available. Here we develop a new self-attention based graph neural network called Hyper-SAGNN applicable to homogeneous and heterogeneous hypergraphs with variable hyperedge sizes. We perform extensive evaluations on multiple datasets, including four benchmark network datasets and two single-cell Hi-C datasets in genomics. We demonstrate that Hyper-SAGNN significantly outperforms the state-of-the-art methods on traditional tasks while also achieving great performance on a new task called outsider identification. Hyper-SAGNN will be useful for graph representation learning to uncover complex higher-order interactions in different applications.

Nowadays, the Convolutional Neural Networks (CNNs) have achieved impressive performance on many computer vision related tasks, such as object detection, image recognition, image retrieval, etc. These achievements benefit from the CNNs outstanding capability to learn the input features with deep layers of neuron structures and iterative training process. However, these learned features are hard to identify and interpret from a human vision perspective, causing a lack of understanding of the CNNs internal working mechanism. To improve the CNN interpretability, the CNN visualization is well utilized as a qualitative analysis method, which translates the internal features into visually perceptible patterns. And many CNN visualization works have been proposed in the literature to interpret the CNN in perspectives of network structure, operation, and semantic concept. In this paper, we expect to provide a comprehensive survey of several representative CNN visualization methods, including Activation Maximization, Network Inversion, Deconvolutional Neural Networks (DeconvNet), and Network Dissection based visualization. These methods are presented in terms of motivations, algorithms, and experiment results. Based on these visualization methods, we also discuss their practical applications to demonstrate the significance of the CNN interpretability in areas of network design, optimization, security enhancement, etc.

Recent advances in 3D fully convolutional networks (FCN) have made it feasible to produce dense voxel-wise predictions of volumetric images. In this work, we show that a multi-class 3D FCN trained on manually labeled CT scans of several anatomical structures (ranging from the large organs to thin vessels) can achieve competitive segmentation results, while avoiding the need for handcrafting features or training class-specific models. To this end, we propose a two-stage, coarse-to-fine approach that will first use a 3D FCN to roughly define a candidate region, which will then be used as input to a second 3D FCN. This reduces the number of voxels the second FCN has to classify to ~10% and allows it to focus on more detailed segmentation of the organs and vessels. We utilize training and validation sets consisting of 331 clinical CT images and test our models on a completely unseen data collection acquired at a different hospital that includes 150 CT scans, targeting three anatomical organs (liver, spleen, and pancreas). In challenging organs such as the pancreas, our cascaded approach improves the mean Dice score from 68.5 to 82.2%, achieving the highest reported average score on this dataset. We compare with a 2D FCN method on a separate dataset of 240 CT scans with 18 classes and achieve a significantly higher performance in small organs and vessels. Furthermore, we explore fine-tuning our models to different datasets. Our experiments illustrate the promise and robustness of current 3D FCN based semantic segmentation of medical images, achieving state-of-the-art results. Our code and trained models are available for download: //github.com/holgerroth/3Dunet_abdomen_cascade.

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