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Forward Learning with Top-Down Feedback: Empirical and Analytical Characterization at ICLR 2024


Core Concepts
"Forward-only" algorithms like PEPITA and Forward-Forward offer biologically plausible solutions to the credit assignment problem in neural networks.
Abstract
This content explores the development and analysis of "forward-only" algorithms, focusing on PEPITA and Forward-Forward. It addresses challenges, theoretical insights, empirical results, comparisons, and future directions. Introduction Discusses the credit assignment problem in machine learning. Highlights issues with backpropagation in neural network training. Bio-Inspired Learning Algorithms Various training rules proposed for artificial neural networks. Table comparing properties and accuracy metrics of different bio-inspired alternatives to BP. Theoretical Analyses Study of online learning with 1-hidden-layer neural networks. Insights into learning dynamics with biologically plausible algorithms. The PEPITA Learning Rule Description of the PEPITA algorithm's clean and modulated forward passes. Formulation of weight updates based on input modulation through error feedback. Testing PEPITA on Deeper Networks Experiments testing PEPITA's performance on deeper networks. Improvement strategies like weight decay, activation normalization, and weight mirroring. On the Relationship Between Forward-Forward and PEPITA Comparison between FF and PEPITA algorithms. Formulation of PEPITA as Hebbian and anti-Hebbian phases. Discussion Addressing challenges in forward-learning algorithms. Limitations and Future Work Acknowledgment of limitations in current algorithms. Suggestions for future research directions. Acknowledgements Support acknowledgment from NIH grant R01EY026025 and NSF grant CCF-1231216. References List of references cited in the content.
Stats
"PEPITA can be approximated by an FA-like algorithm." "Weight decay improved PEPITA's performance by 0.6%." "WM significantly improved alignment between feedback and feedforward weights."
Quotes
"No biological plausibility issue for ML but may help understand shortcomings or offer insights into biological systems." "PEPITA effectively implements 'feedback-alignment' with an adaptive feedback matrix." "PEPITA-TL distinguishes between two forward passes using neuromodulatory signals."

Key Insights Distilled From

by Ravi Sriniva... at arxiv.org 03-25-2024

https://arxiv.org/pdf/2302.05440.pdf
Forward Learning with Top-Down Feedback

Deeper Inquiries

How do forward-only algorithms address scalability issues compared to backpropagation

Forward-only algorithms address scalability issues compared to backpropagation by eliminating the need for a backward pass, which can be computationally expensive and memory-intensive. Backpropagation requires storing gradients for all parameters during the forward pass to update weights in the backward pass. This process becomes increasingly challenging as neural networks grow deeper and more complex. In contrast, forward-only algorithms like PEPITA and Forward-Forward simplify training by replacing the backward pass with additional forward passes, reducing computational overhead and making them more scalable for deep learning tasks.

What are potential implications of aligning feedback weights to feedforward weights in neural network training

Aligning feedback weights to feedforward weights in neural network training has several potential implications: Improved Learning Dynamics: Aligning feedback weights with feedforward weights can enhance learning dynamics by promoting better information flow between layers. Enhanced Generalization: Better alignment between feedback and feedforward connections may lead to improved generalization performance of neural networks on unseen data. Biological Plausibility: Mimicking biological mechanisms where top-down connections play a crucial role in shaping neural activity could lead to more biologically inspired learning algorithms. Reduced Training Complexity: By aligning these weights, it may be possible to simplify training processes and reduce the complexity of weight updates in deep learning models.

How can theoretical frameworks for forward-only algorithms contribute to advancements in deep learning research

Theoretical frameworks for forward-only algorithms contribute significantly to advancements in deep learning research by: Providing Insights into Learning Dynamics: Theoretical analyses help researchers understand how these algorithms learn without a traditional backward pass, shedding light on their underlying principles and mechanisms. Guiding Algorithm Development: Theoretical frameworks offer guidance for developing new variants of forward-learning rules that are both effective and efficient. Enhancing Model Performance: By understanding the theoretical foundations of these algorithms, researchers can optimize hyperparameters, design better architectures, and improve overall model performance. Bridging Biological Inspiration with Machine Learning: Theoretical insights from neuro-inspired learning rules like PEPITA bridge the gap between biological plausibility and machine learning efficiency, paving the way for novel approaches that combine insights from neuroscience with cutting-edge AI techniques. By leveraging theoretical frameworks effectively, researchers can push boundaries in deep learning research while ensuring advancements are grounded in sound mathematical principles.
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