Sáry Gy, Chadaide Z, Tompa T, Köteles K, Kovács Gy, Benedek G
Department of Physiology, Faculty of Medicine, University of Szeged, H-6720, Szeged, Dóm tér 10, Hungary.
Eur J Neurosci. 2007 Apr;25(8):2558-64. doi: 10.1111/j.1460-9568.2007.05494.x.
Perceived boundaries without physical differences between shape and background are called illusory contours (ICs). ICs and real contours (RCs) activate the early processing stages of the macaque visual pathway and the occipitotemporal areas of the human visual system in a similar way. However, it is not known how these contours are processed further in the highest visual areas. We tested how the responses of inferior temporal cortical (IT) neurons of macaque monkeys change in relationship to figures with RCs or ICs. The same set of figures [coloured pictures, ICs and silhouettes (SILs)] was presented to awake, fixating rhesus monkeys while the single-cell activity was recorded in the anterior part of the IT. Most of the neurons responsive to RCs were also responsive to the same shapes presented as ICs. The average net firing rates, however, were significantly lower for the illusory stimuli than for the stimuli in the RC conditions, and the latency of the responses was significantly longer for the ICs than for the RCs. The shape selectivity was found to be different for coloured stimuli and ICs, and similar for SILs and ICs, suggesting the invariance of selectivity to shapes having the same contour but lacking internal surface information. These results suggest different modes of processing of RCs and ICs in the IT, which might explain the differences in their perception.
在形状与背景之间没有物理差异的情况下所感知到的边界被称为虚幻轮廓（ICs）。虚幻轮廓（ICs）和真实轮廓（RCs）以相似的方式激活猕猴视觉通路的早期处理阶段以及人类视觉系统的枕颞区。然而，目前尚不清楚这些轮廓在最高级视觉区域中是如何进一步处理的。我们测试了猕猴颞下皮质（IT）神经元的反应如何随着具有真实轮廓（RCs）或虚幻轮廓（ICs）的图形而变化。在清醒、注视的恒河猴面前呈现同一组图形[彩色图片、虚幻轮廓（ICs）和剪影（SILs）]，同时在颞下皮质（IT）前部记录单细胞活动。大多数对真实轮廓（RCs）有反应的神经元对以虚幻轮廓（ICs）呈现的相同形状也有反应。然而，虚幻刺激的平均净发放率显著低于真实轮廓（RCs）条件下的刺激，并且虚幻轮廓（ICs）的反应潜伏期比真实轮廓（RCs）的显著更长。发现彩色刺激和虚幻轮廓（ICs）的形状选择性不同，而剪影（SILs）和虚幻轮廓（ICs）的形状选择性相似，这表明对具有相同轮廓但缺乏内表面信息的形状的选择性具有不变性。这些结果表明颞下皮质（IT）中真实轮廓（RCs）和虚幻轮廓（ICs）的处理模式不同，这可能解释了它们在感知上的差异。
