Shape Similarity, Better than Semantic Membership, Accounts for the Structure of Visual Object Representations in a Population of Monkey Inferotemporal Neurons
Figure 3
Similarity matrix, hierarchical clustering and PCA of IT population responses to visual objects.
(A) Each pixel in the matrix color-codes the correlation (i.e., similarity) between the neuronal population vectors representing a pair of visual objects. The order of the objects along the axes is defined by the dendrogram produced by hierarchical clustering of the population vectors (to avoid crowding, one every three objects is shown; the complete object set is shown in Fig. 2). The first two branches of the dendrogram (shown at the top) are colored in cyan and magenta. (B) The fraction of animate and inanimate objects is not significantly different in the first two branches of the dendrogram (NS, p>0.1, χ2 test). (C) The proportion of large and small objects is significantly different in the first two branches of the dendrogram (**, p<0.001, χ2 test), (D) Layout of visual objects in the two-dimensional space defined by the first two principal components of the IT population responses (to avoid crowding, only some of the objects are shown). (E) Object area and object ranking along the first principal component are linearly related (r = −0.69, p<0.001, t-test).