In many data-driven applications, higher-order relationships among multiple objects are essential in capturing complex interactions. Hypergraphs, which generalize graphs by allowing edges to connect any number of nodes, provide a flexible and powerful framework for modeling such higher-order relationships. In this work, we introduce hypergraph diffusion wavelets and describe their favorable spectral and spatial properties. We demonstrate their utility for biomedical discovery in spatially resolved transcriptomics by applying the method to represent disease-relevant cellular niches for Alzheimer's disease.

In this paper, we propose HiPoNet, an end-to-end differentiable neural network for regression, classification, and representation learning on high-dimensional point clouds. Our work is motivated by single-cell data which can have very high-dimensionality --exceeding the capabilities of existing methods for point clouds which are mostly tailored for 3D data. Moreover, modern single-cell and spatial experiments now yield entire cohorts of datasets (i.e., one data set for every patient), necessitating models that can process large, high-dimensional point-clouds at scale. Most current approaches build a single nearest-neighbor graph, discarding important geometric and topological information. In contrast, HiPoNet models the point-cloud as a set of higher-order simplicial complexes, with each particular complex being created using a reweighting of features. This method thus generates multiple constructs corresponding to different views of high-dimensional data, which in biology offers the possibility of disentangling distinct cellular processes. It then employs simplicial wavelet transforms to extract multiscale features, capturing both local and global topology from each view. We show that geometric and topological information is preserved in this framework both theoretically and empirically. We showcase the utility of HiPoNet on point-cloud level tasks, involving classification and regression of entire point-clouds in data cohorts. Experimentally, we find that HiPoNet outperforms other point-cloud and graph-based models on single-cell data. We also apply HiPoNet to spatial transcriptomics datasets using spatial coordinates as one of the views. Overall, HiPoNet offers a robust and scalable solution for high-dimensional data analysis.

Graph neural networks (GNNs) have emerged as a powerful tool for tasks such as node classification and graph classification. However, much less work has been done on signal classification, where the data consists of many functions (referred to as signals) defined on the vertices of a single graph. These tasks require networks designed differently from those designed for traditional GNN tasks. Indeed, traditional GNNs rely on localized low-pass filters, and signals of interest may have intricate multi-frequency behavior and exhibit long range interactions. This motivates us to introduce the BLIS-Net (Bi-Lipschitz Scattering Net), a novel GNN that builds on the previously introduced geometric scattering transform. Our network is able to capture both local and global signal structure and is able to capture both low-frequency and high-frequency information. We make several crucial changes to the original geometric scattering architecture which we prove increase the ability of our network to capture information about the input signal and show that BLIS-Net achieves superior performance on both synthetic and real-world data sets based on traffic flow and fMRI data.

Directed graphs are a natural model for many phenomena, in particular scientific knowledge graphs such as molecular interaction or chemical reaction networks that define cellular signaling relationships. In these situations, source nodes typically have distinct biophysical properties from sinks. Due to their ordered and unidirectional relationships, many such networks also have hierarchical and multiscale structure. However, the majority of methods performing node- and edge-level tasks in machine learning do not take these properties into account, and thus have not been leveraged effectively for scientific tasks such as cellular signaling network inference. We propose a new framework called Directed Scattering Autoencoder (DSAE) which uses a directed version of a geometric scattering transform, combined with the non-linear dimensionality reduction properties of an autoencoder and the geometric properties of the hyperbolic space to learn latent hierarchies. We show this method outperforms numerous others on tasks such as embedding directed graphs and learning cellular signaling networks.

We present a machine learning model for the analysis of randomly generated discrete signals, modeled as the points of an inhomogeneous, compound Poisson point process. Like the wavelet scattering transform introduced by Mallat, our construction is naturally invariant to translations and reflections, but it decouples the roles of scale and frequency, replacing wavelets with Gabor-type measurements. We show that, with suitable nonlinearities, our measurements distinguish Poisson point processes from common self-similar processes, and separate different types of Poisson point processes.

We propose a geometric scattering-based graph neural network (GNN) for approximating solutions of the NP-hard maximum clique (MC) problem. We construct a loss function with two terms, one which encourages the network to find highly connected nodes and the other which acts as a surrogate for the constraint that the nodes form a clique. We then use this loss to train an efficient GNN architecture that outputs a vector representing the probability for each node to be part of the MC and apply a rule-based decoder to make our final prediction. The incorporation of the scattering transform alleviates the so-called oversmoothing problem that is often encountered in GNNs and would degrade the performance of our proposed setup. Our empirical results demonstrate that our method outperforms representative GNN baselines in terms of solution accuracy and inference speed as well as conventional solvers like Gurobi with limited time budgets. Furthermore, our scattering model is very parameter efficient with only $\sim$ 0.1\% of the number of parameters compared to previous GNN baseline models.

The prevalence of graph-based data has spurred the rapid development of graph neural networks (GNNs) and related machine learning algorithms. Yet, despite the many datasets naturally modeled as directed graphs, including citation, website, and traffic networks, the vast majority of this research focuses on undirected graphs. In this paper, we propose MagNet, a GNN for directed graphs based on a complex Hermitian matrix known as the magnetic Laplacian. This matrix encodes undirected geometric structure in the magnitude of its entries and directional information in their phase. A charge parameter attunes spectral information to variation among directed cycles. We apply our network to a variety of directed graph node classification and link prediction tasks showing that MagNet performs well on all tasks and that its performance exceeds all other methods on a majority of such tasks. The underlying principles of MagNet are such that it can be adapted to other GNN architectures.

This study presents a proof-of-concept study to assess the prediction of emotional perceptive competency and implicit affective preferences from each other. Predictions are made using linear regression, principal component analysis with linear regression, and support vector machines. Results point to a strong, bidirectional relationship between preference for emotional stimuli and affective competency. This work informs future studies predicting emotion processing abilities in humans and highlights the importance of tailoring interfaces to meet the emotional abilities of the user.

Emotional intelligence has been positively associated with social competence. In addition, attentional responses to emotional information have been associated with psychological characteristics related to mental health. In this study, we used the Microsoft Kinect platform as a tool to examine relationships between responses to emotional information in a gameplay environment and psychological factors. 45 typically developing individuals participated in the study, which involved 1) the Kinect game, requiring participants to engage in unprompted volitional whole-body responses to emotional stimuli, and 2) psychosocial assessments such as the Broader Autism Phenotype Questionnaire (BAPQ) and the Brief Symptom Inventory (BSI). Principal component analysis revealed patterns of gameplay that were associated with psychological characteristics of individuals. Preference for emotional content in general was associated with fewer social difficulties. The present work offers preliminary support for utilizing Kinect video games to understand emotion orienting and social capabilities, and shows that implicit patterns of preference identified during gameplay may relate to psychological and psychiatric phenomena. While the issues are complex and further research is needed, this work may inform the development of novel approaches to diagnostic and therapeutic tools.

Head-mounted eye-tracking systems allow us to observe participants' gaze behaviors in largely unconstrained, real-world settings. We have developed novel, untethered, mobile, low-cost, lightweight, easily-assembled head-mounted eye-tracking devices, comprised entirely of off-the-shelf components, including untethered, point-of-view, sports cameras. In total, the parts we have used cost ~$153, and we suggest untested alternative components that reduce the cost of parts to ~$31. Our device can be easily assembled using hobbying skills and techniques. We have developed hardware, software, and methodological techniques to perform point-of-regard estimation, and to temporally align scene and eye videos in the face of variable frame rate, which plagues low-cost, lightweight, untethered cameras. We describe an innovative technique for synchronizing eye and scene videos using synchronized flashing lights. Our hardware, software, and calibration designs will be made publicly available, and we describe them in detail here, to facilitate replication of our system. We also describe novel smooth-pursuit-based calibration methodology, which affords rich sampling of calibration data while compensating for lack of information regarding the extent of visibility on participants' scene recordings. Validation experiments indicate accuracy within 0.752 degrees of visual angle on average.