Makioka S, Inui T, Yamashita H
Department of Human Sciences, Osaka Women's University, Sakai, Japan.
Perception. 1996;25(8):949-66. doi: 10.1068/p250949.
The psychological space of shapes has been studied in many experiments. However, how shapes are represented in the brain has not been a major issue in psychological literature. Here, the characteristics of internal representation and how it was formed have been considered and an attempt has been made to explain the results of experiments in a unified manner. First, the data of similarity of alphabetic characters and random-dot patterns were reexamined. Multivariate analysis suggested that those patterns were represented by the combination of global features. Second, three-layer neural networks were trained to perform categorization or identity transformation of the same sets of patterns as used in psychological experiments, and activation patterns of the hidden units were analyzed. When the network learned categorization of the patterns, its internal representation was not similar to the representation suggested by psychological experiments. But a network which learned identity transformation of the patterns could acquire such an internal representation. The transformation performed by this kind of network is similar to principal-component analysis in that it projects the input image onto a lower-dimensional space. From these results it is proposed that two-dimensional shapes are represented in human brain by a process like principal-component analysis. This idea is compatible with the findings in neurophysiological studies about higher visual areas.
在许多实验中都对形状的心理空间进行了研究。然而，形状在大脑中是如何表征的，在心理学文献中一直不是一个主要问题。在此，我们考虑了内部表征的特征及其形成方式，并试图以统一的方式解释实验结果。首先，重新审视了字母字符和随机点图案的相似性数据。多变量分析表明，这些图案是由全局特征的组合来表征的。其次，训练了三层神经网络，以执行与心理实验中使用的相同图案集的分类或身份转换，并分析了隐藏单元的激活模式。当网络学习图案的分类时，其内部表征与心理实验所表明的表征并不相似。但是，一个学习图案身份转换的网络可以获得这样的内部表征。这种网络执行的转换类似于主成分分析，因为它将输入图像投影到一个低维空间。从这些结果中可以提出，二维形状在人类大脑中是通过类似于主成分分析的过程来表征的。这一观点与神经生理学研究中关于高级视觉区域的发现是一致的。
