提出新型信用分配机制,让生物合理神经网络在复杂任务上表现优异。
Diffusing Blame: Task-Dependent Credit Assignment in Biologically Plausible Dual-Stream Networks

- 采用兴奋/抑制双流架构,通过误差扩散实现无需反向传播的梯度传递。
- 在MNIST上达96.7%准确率,CIFAR-10建立61.7%基准,突破生物约束限制。
- 揭示任务依赖的信用分配瓶颈,适合研究神经可塑性与类脑学习者。
生物神经回路遵循戴尔原则:每个神经元的突触统一为兴奋或抑制。人工网络若遵守此约束,需协调独立的兴奋与抑制种群,从根本上改变学习中的信用分配方式。尽管已有若干符合生物学原理的学习规则避免了反向传播的权重传输需求,但在严格遵守戴尔原则下,性能仍难以超越MNIST。误差扩散(ED)最初在双流兴奋/抑制架构中提出,通过将全局误差信号路由至所有层,无需传输转置前向权重或依赖随机反馈矩阵来驱动学习。该方法能否在戴尔原则下扩展至监督分类与强化学习仍未知。本文引入模误差路由,拓展误差扩散至多类别分类,并证明采用该方法的双流架构在MNIST上达到96.7%准确率,在CIFAR-10上建立61.7%基准,证实即使在严格遵守戴尔原则下也可实现表征学习。针对分类任务,提出三类领域特定改进:层间逻辑门宽度自适应、批次中心化类别误差信号、非对称初始化;消融分析显示其相对重要性在MNIST与CIFAR-10间反转,暴露出单基准评估无法揭示的任务依赖信用分配瓶颈。在强化学习中,将ED与近端策略优化(PPO)结合,在Google Brax连续控制任务及Craftax开放探索任务上评估,结果表明ED-PPO在无反向传播基线中表现具有竞争力。
原文摘要 · Abstract (English)
Biological neural circuits obey Dale's principle: each neuron's synapses are uniformly excitatory or inhibitory. Artificial networks that respect this constraint must coordinate separate excitatory and inhibitory populations, fundamentally changing how credit is assigned during learning. Several biologically plausible learning rules avoid backpropagation's weight transport requirement, but it has been difficult to achieve strong performance under Dale's principle beyond MNIST. Error Diffusion (ED) was originally proposed in a dual-stream excitatory/inhibitory architecture, where learning is driven by routing global error signals to all layers without transporting transposed forward weights or relying on random feedback matrices. Whether such a rule can scale under Dale's principle across both supervised classification and reinforcement learning remains unknown. Here, we introduce modulo error routing to extend Error Diffusion beyond binary classification, and show that a dual-stream excitatory/inhibitory architecture trained with this method achieves 96.7% on MNIST and establishes a 61.7% baseline on CIFAR-10, demonstrating that representation learning is possible even when strictly enforcing Dale's principle. For the classification setting, we introduce three domain-specific innovations: layer-specific sigmoid widths, batch-centered class error signals, and asymmetric initialization, and ablation analysis reveals that their relative importance reverses between MNIST and CIFAR-10, exposing task-dependent credit-assignment bottlenecks invisible to single-benchmark evaluation. In reinforcement learning, we integrate ED with Proximal Policy Optimization (PPO) and evaluate it on continuous-control tasks in Google Brax and on Craftax, an open-ended exploration task. We show that ED-PPO achieves competitive performance relative to Direct Feedback Alignment, a backpropagation-free baseline.
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