Neuroscience: A Face's Journey through Space and Time.

Faces are complex objects of great variety, which the visual brain somehow manages to organize by similarity. Two such orderings in fact exist and one, a new study finds, is transformed into the other over time, enhancing a face's distinctiveness.

Convolutional neural networks explain tuning properties of anterior, but not middle, face-processing areas in macaque inferotemporal cortex.

Recent computational studies have emphasized layer-wise quantitative similarity between convolutional neural networks (CNNs) and the primate visual ventral stream. However, whether such similarity holds for the face-selective areas, a subsystem of the higher visual cortex, is not clear. Here, we extensively investigate whether CNNs exhibit tuning properties as previously observed in different macaque face areas.

A mixture of sparse coding models explaining properties of face neurons related to holistic and parts-based processing.

Experimental studies have revealed evidence of both parts-based and holistic representations of objects and faces in the primate visual system. However, it is still a mystery how such seemingly contradictory types of processing can coexist within a single system. Here, we propose a novel theory called mixture of sparse coding models, inspired by the formation of category-specific subregions in the inferotemporal (IT) cortex.

Genealogy of Conjugated Acyclic Polyenes.

Based on the total π-electron energies s of Hückel Molecular Orbital (HMO) method for all the possible isomers of conjugated acyclic polyenes (C₂H₂) up to = 7, the structure-stability relation of the possible isomers was analyzed. It was shown that the mean length of conjugation can roughly predict the ordering of stability among isomers, while the -index, or Hosoya-index, can almost perfectly reproduce their stability. Further, the genealogy of the conjugated acyclic polyene family was obtained by drawing systematic diagrams connecting these isomers of different , and governed by several simple rules.

Learning Visual Spatial Pooling by Strong PCA Dimension Reduction.

In visual modeling, invariance properties of visual cells are often explained by a pooling mechanism, in which outputs of neurons with similar selectivities to some stimulus parameters are integrated so as to gain some extent of invariance to other parameters. For example, the classical energy model of phase-invariant V1 complex cells pools model simple cells preferring similar orientation but different phases. Prior studies, such as independent subspace analysis, have shown that phase-invariance properties of V1 complex cells can be learned from spatial statistics of natural inputs.

A Hierarchical Statistical Model of Natural Images Explains Tuning Properties in V2.

Previous theoretical and experimental studies have demonstrated tight relationships between natural image statistics and neural representations in V1. In particular, receptive field properties similar to simple and complex cells have been shown to be inferable from sparse coding of natural images. However, whether such a relationship exists in higher areas has not been clarified.

Multinomial Bayesian learning for modeling classical and nonclassical receptive field properties.

We study the interplay of Bayesian inference and natural image learning in a hierarchical vision system, in relation to the response properties of early visual cortex. We particularly focus on a Bayesian network with multinomial variables that can represent discrete feature spaces similar to hypercolumns combining minicolumns, enforce sparsity of activation to learn efficient representations, and explain divisive normalization. We demonstrate that maximal-likelihood learning using sampling-based Bayesian inference gives rise to classical receptive field properties similar to V1 simple cells and V2 cells, while inference performed on the trained network yields nonclassical context-dependent response properties such as cross-orientation suppression and filling in.

How can we explain the stability of conjugated hydrocarbon-and heterosubstituted networks by topological descriptors?

Correlation between the π-electronic stability (Hückel's Eπ) and several topological descriptors, including Hosoya's Z, Wiener's W, and Randic's 1χ , was compared for the isomeric acyclic conjugated hydrocarbon molecules from hexatriene to decapentaene. From the analysis of the best descriptor Z and mean length of conjugated paths L, the origin of π-electronic stability was logically explained. The effect of heteroatom substitution to polyenes was studied and analyzed by graph-theoretical techniques.

Sparse codes of harmonic natural sounds and their modulatory interactions.

Sparse coding and its related theories have been successful to explain various response properties of early stages of sensory information processing such as primary visual cortex and peripheral auditory system, which suggests that the emergence of such properties results from adaptation of the nerve system to natural stimuli. The present study continues this line of research in a higher stage of auditory processing, focusing on harmonic structures that are often found in behaviourally important natural sound like animal vocalization. It has been physiologically shown that monkey primary auditory cortices (A1) have neurons with response properties capturing such harmonic structures: their response and modulation peaks are often found at frequencies that are harmonically related to each other.

Important mathematical structures of the topological index Z for tree graphs.

Mathematical importance of the topological index, ZG, or the so-called Hosoya index is stressed by presenting and giving supporting evidence for the proposed conjecture. That is, for a given pair of positive integers (n1or=3), with Z(G1) = n1 and Z(G2) = n2.

Analysis of the relationship among the graphs isomorphic to multilayered cyclic fence graphs (MLCFG).

Multilayered cyclic fence graphs (MLCFG, E(m,n), F(m,n), D(m,n), G(m,n), X(m,n)) are proposed to be defined, all of which are composed of m 2n-membered cycles with periodic bridging. They are also cubic and bipartite. Hamiltonian wheel graph, H (n,[j(k)]), and parallelogram-shaped polyhex graph are also defined.