Open research questions in Neural Networks and Applications
29 unresolved questions extracted from the limitations and future-work sections of 455 Neural Networks and Applications papers in our library. Each links back to the study that raised it.
What the literature leaves open
This improvement excludes the time to compute TDA features, which currently takes 968 ms per step and remains a major limitation. By learning the relevance of each RNN based on system state, the model provided reliable predictions even when training data is limited.
Topology-informed deep learning estimation using feedforward attention layer for high-rate state estimation · 2026 · DOIFor instance, ML algorithms train NN weights by moving them along a low-dimensional subspace of their allowed values, but this implicitly low-dimensional learning structure is not properly exploited to improve training because its nature is not well understood.
Explaining Machine Learning and Memorization with Statistical Mechanics · 2026These findings underscore that both autoregressive feedback and immediate exogenous context are essential for the exact characterization of topological phases, establishing NARX as a robust framework for deriving governing laws in complex quantum systems, where analytical solutions remain elusive.
Deterministic Mapping of Topological Phases via Autoregressive Exogenous Neural Networks · 2026The current VASM implementation indexes memories by their TERA coordinate at storage time. This is a snapshot of the generation state — it does not capture the trajectory of the TERA coordinate through the generation of the stored content. Future work should explore trajectory-indexed storage: instead of a single TERA point per memory, store the TERA path (the sequence of TERA coordinates during generation, the same “generation worldline” whose speed defines HeartScale drift in WP-02), and query by path similarity. The information-geometric metric requested as future work in Revision 1 is now adopted in §2.2: for product- Bernoulli Meji measures the KL divergence factorizes and the symmetric Fisher–Rao geodesic has the closed v2_d)2. Distances are computed on the conserved maniform d_FR = fold Σ_𝜅 (WP-01 §2.1a). The remaining open direction is the trajectory indexing above.
Vortex-Addressed Semantic Memory: Retrieval by Archetypal Geometry Rather Than Embedding Similarity · 2026 · DOIGranger Causality marks the final measure covered in this review, and thus the conclusion of the in-depth coverage of the eleven information-theoretic time-series measures. Collectively, we have presented a unified and accessible guide to these eleven key measures for analyzing time series data, with a particular focus on their applications in computational neuroscience. Through a novel schematic overview (with measure-specific decompositions in each section) and a systematic tabular summary, we have sought to clarify conceptual distinctions between measures—such as directionality, temporal dependence, and dimensional scope—and to bridge terminology across disparate literatures. Our aim has been not only to consolidate fundamental definitions but also to offer an integrative perspective that enables researchers with a wide range of background knowledge depths to navigate this methodological landscape with greater fluency. While our examples and emphasis here have focused on neural time-series data, we note that all measures are broadly applicable across diverse scientific domains. Resources like the UEA/UCR Time Series Classification repository [120, 121] provide compelling examples of diverse time-series datasets—from beef spectrograms to yoga pose angles to goose vocalizations—that could benefit from this conceptual framework to yield new insights into how information-theoretic measures relate to each other when computed on diverse empirical data. Each measure in this guide offers a unique lens on dynamics such as uncertainty, dependence, and predictability. Developing an intuitive grasp of how these measures interrelate and differ lays the foundation for richer, more integrative analyses of complex systems like the brain. We hope this guide serves as a starting point, upon which future work may extend this foundation by incorporating additional measures, refining estimation techniques, or exploring emerging applications.
1 Future Research Directions The CFN framework opens several promising avenues for future research: Theoretical Foundations Further work is needed to for- malize the expressive power of different CFN configurations and establish theoretical guarantees on their approximation capabilities.
Compositional Function Networks: A High-Performance Alternative to Deep Neural Networks with Built-in Interpretability · 2026 · DOIAdditionally, the evalu- ation does not account for potential hardware-specific constraints or noise effects in quantum computations. We are limited to a specific dataset and predefined PQC configurations, which may not generalize to other tasks or quantum hardware.
Practical insights on the effect of different encodings, ansätze and measurements in quantum and hybrid convolutional neural networks · 2026 · DOIHowever, realizing QLSTM’s full capabilities necessitates further research into model validation across diverse conditions, systematic hyperparameter optimization, hardware noise resilience, and applications to correlated renewable forecasting problems.
Quantum long short-term memory (QLSTM) vs. classical LSTM in time series forecasting: a comparative study in solar power forecasting · 2024 · DOIEach subsec- tion addresses a distinct dimension of the design space preemptively—not because these concerns were raised exter- nally, but because transparent reasoning about scope, trade- offs, and open questions is a structural property of the paper.
A central open question is whether this gap reflects only implementation and optimization limitations, or whether architectural features of spiking computation impose unfavorable learnability constraints as sequence length increases.
Feedforward spiking neural networks are not transformers (yet): a learning-theoretic framework for long-range dependencies and biological efficiency · 2026 · DOIThe workshop fostered interactions across disciplines and highlighted a number of open problems and future directions for the mathematical foundations of machine learning.
A limitation of the present study is that all experiments are conducted on the static-load FC1 subset of the IEEE PHM 2014 dataset.
Sensitivity analysis of a CNN–LSTM prognostic framework for proton exchange membrane fuel cells: Effects of sliding window size and training data allocation · 2026 · DOIFor small networks, we constructed the complete ``catalogs'' of network-function performance, which revealed that computational capacity varies widely across architectures and that most networks show poor performance, and most functions are hard to compute.
Identifying structural design principles shaping the computational abilities of recurrent neural networks · 2026But many open questions remain, among them the origin of so called grokking: the abrupt, delayed onset of generalization after prolonged apparent overfitting.
Noise-Driven Escape from Metastable Phases explains Grokking in Deep Neural Networks · 2026Finally, we conclude and discuss benchmarks, evaluation criteria, and open challenges, such as the ability to identify causal links or directionality of communication, to facilitate future research for bridging interpretable brain dynamics with reliable neural decoding.
Machine Learning Methods for Studying Latent Neural Activity Dynamics · 2026It remains to be studied how noise correlations among nodes affect the learning capabilities of the RKM.
Unsupervised and probabilistic learning with Contrastive Local Learning Networks: The Restricted Kirchhoff Machine · 2026 · DOIFinally, we have argued that these findings should not be limited to the experimental situation we have used, but are natu- rally and usefully related to many other serially-organized tasks, es- pecially to music.
Most-cited papers in Neural Networks and Applications
- Deep learning for AI · Communications of the ACM · 2021 · 583 citations
- A Survey on Deep Neural Network Pruning: Taxonomy, Comparison, Analysis, and Recommendations · IEEE Transactions on Pattern Analysis and Machine Intelligence · 2024 · 404 citations
- Reminder of the First Paper on Transfer Learning in Neural Networks, 1976 · Informatica · 2020 · 219 citations
- Adan: Adaptive Nesterov Momentum Algorithm for Faster Optimizing Deep Models · IEEE Transactions on Pattern Analysis and Machine Intelligence · 2024 · 129 citations
- Dynamics of heterogeneous Hopfield neural network with adaptive activation function based on memristor · Neural Networks · 2024 · 113 citations
- A Novel Centralized Federated Deep Fuzzy Neural Network with Multi-objectives Neural Architecture Search for Epistatic Detection · IEEE Transactions on Fuzzy Systems · 2024 · 92 citations
- Chaotic dynamical system of Hopfield neural network influenced by neuron activation threshold and its image encryption · Nonlinear Dynamics · 2024 · 92 citations
- A Selective Overview of Deep Learning · Statistical Science · 2021 · 88 citations
- Multidirectional Multidouble-Scroll Hopfield Neural Network With Application to Image Encryption · IEEE Transactions on Systems Man and Cybernetics Systems · 2024 · 86 citations
- Intuitive physics learning in a deep-learning model inspired by developmental psychology · Nature Human Behaviour · 2022 · 80 citations
Most recent work
- Function aligns with geometry in locally connected neuronal networks · bioRxiv · 2026
- High-frequency spike inference with particle Gibbs sampling · eLife · 2026
- Precise calcium-to-spike inference using biophysical generative models · bioRxiv · 2026
- Better Neural Network Expressivity: Subdividing the Simplex · 2026
- The effect of label noise on the information content of neural representations · Frontiers in Physics · 2026
- Practical insights on the effect of different encodings, ansätze and measurements in quantum and hybrid convolutional neural networks · Quantum Machine Intelligence · 2026
- A Memory-Enhanced Fractional Probabilistic Self-Organizing Map · International Journal of Computational Intelligence and Applications · 2026
- Hopfield Networks as Models of Emergent Function in Biology · Annual Review of Biophysics · 2026
- Convergence of Implicit Gradient Descent for Training Two-Layer Physics-Informed Neural Networks · East Asian Journal on Applied Mathematics · 2026
- Elastic Patterns: A Deformation-Based Approach to Interpretable Classification · Mathematics · 2026
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