Data from: Dynamic population codes of multiplexed stimulus features in primate area MT

The middle-temporal area (MT) of primate visual cortex is critical in the analysis of visual motion. Single-unit studies suggest that the response dynamics of neurons within area MT depend on stimulus features, but how these dynamics emerge at the population level, and how feature representations interact, is not clear. Here, we used multivariate classification analysis to study how stimulus features are represented in the spiking activity of populations of neurons in area MT of marmoset monkey. Using Representational Similarity Analysis (RSA) we distinguished the emerging representations of moving grating and dot field stimuli. We show that representations of stimulus orientation, spatial frequency and speed are evident near the onset of the population response, while the representation of stimulus direction is slower to emerge and sustained throughout the stimulus-evoked response. We further found a spatiotemporal asymmetry in the emergence of direction representations. Representations for high spatial frequencies and low temporal frequencies are initially orientation-dependent, while those for high temporal frequencies and low spatial frequencies are more sensitive to motion direction. Our analyses reveal a complex interplay of feature representations in area MT population response that may explain the stimulus-dependent dynamics of motion vision.灵长类视觉皮层的中颞区（middle-temporal area, MT）在视觉运动分析中发挥关键作用。单神经元研究表明，MT脑区神经元的响应动力学特性依赖于刺激特征，但目前尚不清楚这些动力学特性如何在群体层面显现，以及特征表征之间如何相互作用。本研究采用多变量分类分析方法，探究狨猴MT脑区神经元群体锋电位活动中的刺激特征表征方式。借助表征相似性分析（Representational Similarity Analysis, RSA），本研究区分了运动光栅与点场刺激的动态表征。研究发现，刺激方位、空间频率与速度的表征在群体响应初始阶段便已显现，而刺激方向的表征则出现较慢，并在整个刺激诱发的响应过程中持续存在。本研究还发现方向表征的显现过程存在时空不对称性：高空间频率与低时间频率的刺激表征最初依赖于方位信息，而高时间频率与低空间频率的刺激表征则对运动方向更为敏感。本研究的分析揭示了MT脑区群体响应中特征表征间的复杂相互作用，这或许可以解释运动视觉中依赖于刺激的动力学特性。