Tarkiainen A, Cornelissen P L, Salmelin R
Brain Research Unit, Low Temperature Laboratory, Helsinki University of Technology, Finland.
Brain. 2002 May;125(Pt 5):1125-36. doi: 10.1093/brain/awf112.
Neurones in the human inferior occipitotemporal cortex respond to specific categories of images, such as numbers, letters and faces, within 150-200 ms. Here we identify the locus in time when stimulus-specific analysis emerges by comparing the dynamics of face and letter-string perception in the same 10 individuals. An ideal paradigm was provided by our previous study on letter-strings, in which noise-masking of stimuli revealed putative visual feature processing at 100 ms around the occipital midline followed by letter-string-specific activation at 150 ms in the left inferior occipitotemporal cortex. In the present study, noise-masking of cartoon-like faces revealed that the response at 100 ms increased linearly with the visual complexity of the images, a result that was similar for faces and letter-strings. By 150 ms, faces and letter-strings had entered their own stimulus-specific processing routes in the inferior occipitotemporal cortex, with identical timing and large spatial overlap. However, letter-string analysis lateralized to the left hemisphere, whereas face processing occurred more bilaterally or with right-hemisphere preponderance. The inferior occipitotemporal activations at approximately 150 ms, which take place after the visual feature analysis at approximately 100 ms, are likely to represent a general object-level analysis stage that acts as a rapid gateway to higher cognitive processing.
人类枕颞下回皮质中的神经元在150 - 200毫秒内对特定类别的图像，如数字、字母和面孔做出反应。在此，我们通过比较10名相同个体中面孔和字母串感知的动态过程，确定刺激特异性分析出现的时间点。我们之前关于字母串的研究提供了一个理想的范式，其中刺激的噪声掩蔽揭示了枕叶中线周围100毫秒时假定的视觉特征处理，随后在左侧枕颞下回皮质中150毫秒时出现字母串特异性激活。在本研究中，卡通样面孔的噪声掩蔽显示，100毫秒时的反应随图像的视觉复杂性呈线性增加，面孔和字母串的结果相似。到150毫秒时，面孔和字母串在枕颞下回皮质中进入了各自的刺激特异性处理路径，时间相同且空间重叠较大。然而，字母串分析偏向于左半球，而面孔处理更多地双侧进行或右半球占优势。大约150毫秒时的枕颞下回激活发生在大约100毫秒的视觉特征分析之后，可能代表一个一般的物体水平分析阶段，作为通向更高认知处理的快速通道。
