Continual Lifelong Learning with Neural Networks: A Review

TL;DR

This review discusses the challenges of lifelong learning in neural networks, compares existing approaches to mitigate catastrophic forgetting, and explores biological inspirations like plasticity and memory replay.

Contribution

It provides a comprehensive summary of current methods and biological insights addressing lifelong learning challenges in neural networks.

Findings

Neural networks struggle with catastrophic forgetting in lifelong learning.

Biological mechanisms inspire new approaches to continual learning.

Existing methods partially mitigate forgetting but face scalability issues.

Abstract

Humans and animals have the ability to continually acquire, fine-tune, and transfer knowledge and skills throughout their lifespan. This ability, referred to as lifelong learning, is mediated by a rich set of neurocognitive mechanisms that together contribute to the development and specialization of our sensorimotor skills as well as to long-term memory consolidation and retrieval. Consequently, lifelong learning capabilities are crucial for autonomous agents interacting in the real world and processing continuous streams of information. However, lifelong learning remains a long-standing challenge for machine learning and neural network models since the continual acquisition of incrementally available information from non-stationary data distributions generally leads to catastrophic forgetting or interference. This limitation represents a major drawback for state-of-the-art deep neural network models that typically learn representations from stationary batches of training data, thus without accounting for situations in which information becomes incrementally available over time. In this review, we critically summarize the main challenges linked to lifelong learning for artificial learning systems and compare existing neural network approaches that alleviate, to different extents, catastrophic forgetting. We discuss well-established and emerging research motivated by lifelong learning factors in biological systems such as structural plasticity, memory replay, curriculum and transfer learning, intrinsic motivation, and multisensory integration.