Early Numerosity Encoding in Visual Cortex Is Not Sufficient for the Representation of Numerical Magnitude
Early Numerosity Encoding in Visual Cortex Is Not Sufficient for the Representation of Numerical Magnitude
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DOI：
10.1162/jocn_a_01320
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发表时间：
2018-12-01
影响因子：
3.2
通讯作者：
Park, Joonkoo
中科院分区：
文献类型：
--
作者：
Fornaciai, Michele;Park, Joonkoo
最近的研究表明，视觉呈现的点阵列的数量在潜伏期的极早期就在低级视觉皮层中表现出来。然而，这样的早期神经特征是否反映了数字的感知表征仍然未知。或者，这样的签名可以指示点阵列刺激在变成感知的数字表示之前的原始感觉表示。在这里，我们通过使用连通性错觉来解决这个问题，即与包含孤立点的数组相比，具有成对连接点的数组被认为数量较少。在两个独立的实验中，我们使用 EEG 和 fMRI，测量了对由 16 或 32 个点组成的点阵刺激的神经反应，这些点可以是孤立的，也可以是成对连接的。使用多变量模式分析，在 EEG 实验中刺激开始后 150 毫秒后的神经活动中以及在 fMRI 实验中的 V3 区域中观察到连接性的影响，它反映了视觉刺激分割为感知单元的效果。相比之下，100 毫秒之前和 V2 区域的早期神经活动受到数量的严格调节，无论连通性如何，这表明这种早期活动反映了感知分割之前点阵列的感觉表征。因此，我们的研究结果表明，早期视觉皮层中数字的神经表征不足以用于视觉数字感知，并且表明数字的感知编码发生在稍后在区域 V3 中进行的分割过程中或之后。
Recent studies have demonstrated that the numerosity of visually presented dot arrays is represented in low-level visual cortex extremely early in latency. However, whether or not such an early neural signature reflects the perceptual representation of numerosity remains unknown. Alternatively, such a signature may indicate the raw sensory representation of the dot-array stimulus before becoming the perceived representation of numerosity. Here, we addressed this question by using the connectedness illusion, whereby arrays with pairwise connected dots are perceived to be less numerous compared with arrays containing isolated dots. Using EEG and fMRI in two independent experiments, we measured neural responses to dot-array stimuli comprising 16 or 32 dots, either isolated or pairwise connected. The effect of connectedness, which reflects the segmentation of the visual stimulus into perceptual units, was observed in the neural activity after 150 msec post stimulus onset in the EEG experiment and in area V3 in the fMRI experiment using a multivariate pattern analysis. In contrast, earlier neural activity before 100 msec and in area V2 was strictly modulated by numerosity regardless of connectedness, suggesting that this early activity reflects the sensory representation of a dot array before perceptual segmentation. Our findings thus demonstrate that the neural representation for numerosity in early visual cortex is not sufficient for visual number perception and suggest that the perceptual encoding of numerosity occurs at or after the segmentation process that takes place later in area V3.