论文标题

混合预测编码:推断,快速和缓慢

Hybrid Predictive Coding: Inferring, Fast and Slow

论文作者

Tschantz, Alexander, Millidge, Beren, Seth, Anil K, Buckley, Christopher L

论文摘要

预测编码是皮质神经活动的影响模型。它提出,通过依次最大程度地减少“预测误差”(预测数据和观察到的数据之间的差异)来提供感知信念。该提议中隐含的观念是,感知需要多个神经活动的周期。这与证据表明,视觉感知的几个方面(包括复杂的对象识别形式)是由最初的“馈电扫描”引起的,该“馈电扫描”出现在快速的时间表上,该时间表排除了实质性的复发活动。在这里,我们建议可以将馈电扫描理解为表现摊销的推理,并且可以将重复的处理理解为执行迭代推断。我们提出了一个混合预测编码网络,该网络以原则性的方式结合了迭代和摊销推断,通过对单个目标函数的双重优化来描述两者。我们表明,可以在生物学上合理的神经体系结构中实施该方案,该神经架构近似使用本地HEBBIAN更新规则来近似于贝叶斯的推理。我们证明,混合预测性编码模型结合了摊销和迭代推断的好处 - 在维持上下文敏感性,精度和样本效率的迭代推理方案的同时,获得了快速且计算的廉价感知推断,以获取熟悉的数据。此外,我们展示了我们的模型如何固有地对其不确定性和适应性平衡迭代和摊销推断,以使用最低计算费用获得准确的信念。混合预测编码为视觉感知期间观察到的前馈活动和经常性活动的功能相关性提供了新的观点,并提供了对视觉现象学不同方面的新见解。

Predictive coding is an influential model of cortical neural activity. It proposes that perceptual beliefs are furnished by sequentially minimising "prediction errors" - the differences between predicted and observed data. Implicit in this proposal is the idea that perception requires multiple cycles of neural activity. This is at odds with evidence that several aspects of visual perception - including complex forms of object recognition - arise from an initial "feedforward sweep" that occurs on fast timescales which preclude substantial recurrent activity. Here, we propose that the feedforward sweep can be understood as performing amortized inference and recurrent processing can be understood as performing iterative inference. We propose a hybrid predictive coding network that combines both iterative and amortized inference in a principled manner by describing both in terms of a dual optimization of a single objective function. We show that the resulting scheme can be implemented in a biologically plausible neural architecture that approximates Bayesian inference utilising local Hebbian update rules. We demonstrate that our hybrid predictive coding model combines the benefits of both amortized and iterative inference -- obtaining rapid and computationally cheap perceptual inference for familiar data while maintaining the context-sensitivity, precision, and sample efficiency of iterative inference schemes. Moreover, we show how our model is inherently sensitive to its uncertainty and adaptively balances iterative and amortized inference to obtain accurate beliefs using minimum computational expense. Hybrid predictive coding offers a new perspective on the functional relevance of the feedforward and recurrent activity observed during visual perception and offers novel insights into distinct aspects of visual phenomenology.

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