Central auditory neurons display flexible feature recombination functions
Central auditory neurons display flexible feature recombination functions
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DOI：
10.1152/jn.00637.2013
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发表时间：
2014-03-01
影响因子：
2.5
通讯作者：
Gentner, Timothy Q.
中科院分区：
文献类型：
--
作者：
Kozlov, Andrei S.;Gentner, Timothy Q.
自然刺激的识别需要选择性和不变性的结合。经典的神经生物学模型分别通过为每个皮层神经元分配一个相当于逻辑“与”的计算或一个相当于逻辑“或”的计算来实现选择性和不变性。“一个强大的类似OR的操作是MAX函数，它计算输入活动的最大值。MAX函数在计算机视觉中经常被用来实现不变性，并被认为是视觉皮层中的关键操作。在这里，我们探讨了计算的选择性和不变性的听觉系统的鸣禽，使用自然的刺激。我们提出两个相关问题：听觉系统中存在MAX运算吗？它是由专门的“MAX”神经元实现的，就像视觉中假设的那样？通过分析单个神经元对刺激组合的响应，我们系统地对实现的特征重组函数的空间进行采样。虽然我们经常观察到MAX函数，但我们发现实现它的神经元也很容易实现其他操作，包括类似AND的响应。然后，我们表明，感觉适应，神经回路的一个无处不在的属性，导致这些操作之间的过渡，在个别神经元，违反了固定的神经元到计算映射假设在国家的最先进的对象识别模型。然而，这些过渡，雅阁符合神经电路模型的预测，包括分裂归一化和可变多项式非线性尖峰阈值。由于这些生物物理特性与特定的感觉方式无关，而是通用的，因此本研究中在听觉系统中展示的灵活的神经元到计算映射可能是一种通用特性。
Recognition of natural stimuli requires a combination of selectivity and invariance. Classical neurobiological models achieve selectivity and invariance, respectively, by assigning to each cortical neuron either a computation equivalent to the logical "AND" or a computation equivalent to the logical "OR." One powerful OR-like operation is the MAX function, which computes the maximum over input activities. The MAX function is frequently employed in computer vision to achieve invariance and considered a key operation in visual cortex. Here we explore the computations for selectivity and invariance in the auditory system of a songbird, using natural stimuli. We ask two related questions: does the MAX operation exist in auditory system? Is it implemented by specialized "MAX" neurons, as assumed in vision? By analyzing responses of individual neurons to combinations of stimuli we systematically sample the space of implemented feature recombination functions. Although we frequently observe the MAX function, we show that the same neurons that implement it also readily implement other operations, including the AND-like response. We then show that sensory adaptation, a ubiquitous property of neural circuits, causes transitions between these operations in individual neurons, violating the fixed neuron-to-computation mapping posited in the state-of-the-art object-recognition models. These transitions, however, accord with predictions of neural-circuit models incorporating divisive normalization and variable polynomial nonlinearities at the spike threshold. Because these biophysical properties are not tied to a particular sensory modality but are generic, the flexible neuron-to-computation mapping demonstrated in this study in the auditory system is likely a general property.