Centro Atómico Bariloche and Instituto Balseiro San Carlos de Bariloche, Argentina.
Front Comput Neurosci. 2010 Nov 23;4:145. doi: 10.3389/fncom.2010.00145. eCollection 2010.
Sensory stimuli are usually composed of different features (the what) appearing at irregular times (the when). Neural responses often use spike patterns to represent sensory information. The what is hypothesized to be encoded in the identity of the elicited patterns (the pattern categories), and the when, in the time positions of patterns (the pattern timing). However, this standard view is oversimplified. In the real world, the what and the when might not be separable concepts, for instance, if they are correlated in the stimulus. In addition, neuronal dynamics can condition the pattern timing to be correlated with the pattern categories. Hence, timing and categories of patterns may not constitute independent channels of information. In this paper, we assess the role of spike patterns in the neural code, irrespective of the nature of the patterns. We first define information-theoretical quantities that allow us to quantify the information encoded by different aspects of the neural response. We also introduce the notion of synergy/redundancy between time positions and categories of patterns. We subsequently establish the relation between the what and the when in the stimulus with the timing and the categories of patterns. To that aim, we quantify the mutual information between different aspects of the stimulus and different aspects of the response. This formal framework allows us to determine the precise conditions under which the standard view holds, as well as the departures from this simple case. Finally, we study the capability of different response aspects to represent the what and the when in the neural response.
感觉刺激通常由不同的特征（即“什么”）组成，这些特征以不规则的时间出现（即“何时”）。神经反应通常使用尖峰模式来表示感觉信息。据假设，“什么”由诱发模式的身份（即“模式类别”）编码，而“何时”由模式的时间位置（即“模式定时”）编码。然而，这种标准观点过于简单化。在现实世界中，“什么”和“何时”可能不是可分离的概念，例如，如果它们在刺激中相关。此外，神经元动力学可以调节模式定时与模式类别相关联。因此，模式的定时和类别可能不构成独立的信息通道。在本文中，我们评估了尖峰模式在神经编码中的作用，而不考虑模式的性质。我们首先定义了信息理论数量，这些数量允许我们量化神经反应不同方面编码的信息。我们还引入了模式时间位置和类别之间协同作用/冗余的概念。随后，我们建立了刺激中“什么”和“何时”与模式定时和类别之间的关系。为此，我们量化了刺激和反应不同方面之间的互信息。这个形式框架使我们能够确定标准观点成立的精确条件，以及与这种简单情况的偏离。最后，我们研究了不同反应方面在神经反应中表示“什么”和“何时”的能力。
