Analysis of connectivity in the cat cerebral cortex

Abstract

The mammalian cerebral cortex is innervated by a large number of corticocortical connections. The number of connections makes it difficult to understand the organization of the cortical network. Nonetheless, conclusions about the organization of cortical systems drawn from examining connectional data have often been made in a speculative and informal manner, unsupported by any analytic treatment. Recently, progress has been made toward more systematic ways of extracting organizing principles from data on the network of connections between cortical areas of the monkey. In this article, we extend these approaches to the cortical systems of the cat. We collated information from the neuroanatomical literature about the corticocortical connections of the cat. This collation incorporated 1139 reported corticocortical connections between 65 cortical areas. We have previously used an optimization technique (Scannell and Young, 1993) to analyze this database in order to represent the connectional organization of cortical systems in the cat. Here, we report the connectional database and analyze it in a number of further ways. First, we employed rules from Felleman and Van Essen (1991) to investigate hierarchical relations among the areas. Second, we compared quantitatively the results of the optimization method with the results of the hierarchical method. Third, we examined quantitatively whether simple connection rules, which may reflect the development and evolution of the cortex, can account for the experimentally identified corticocortical connections in the database. The results showed, first, that hierarchical rules, when applied to the cat visual system, define a largely consistent hierarchy. Second, in both auditory and visual systems, the ordering of areas by hierarchical analysis and by optimization analysis was statistically significantly related. Hence, independent analyzes concur broadly in their ordering of areas in the cortical hierarchies. Third, the majority of corticocortical connections, and much of the pattern of connectivity, were accounted for by a simple “nearest-neighbor-or-next-door-but-one” connection rule, which may suggest one of the mechanisms by which the development of cortical connectivity is controlled.

Organization, development and function of complex brain networks

“…Most structural analyses of brain networks have been carried out on datasets describing the large-scale connection patterns of the cerebral cortex of rat [20], cat [21,22], and monkey [23] -structural connection data for the human brain is largely missing [24]. These analyses have revealed several organizational principles expressed within structural brain networks.…”

The Neural-Cognitive Basis of the Jamesian Stream of Thought

“…Similarly, the jingle in the back of the mind might be P-conscious without being A-conscious. Blakemore, and Young (1995;Scannell et al, 1999) have performed detailed analyses of cortical connectivity in the cat and found that the cortical regions can be divided into four highly interconnected groups: the visual system, the auditory system, the somatosensory-motor system, and the frontal-hippocampal system. Based on the previous discussion, we can postulate that the establishment of focal awareness requires involvement of the frontal-hippocampal system.…”

Global optimization of cerebral cortex layout

“…Such a bifurcation can save Ϸ10% of the corresponding length of two separate connections (4,14). However, cerebral connection compendia only describe links between pairs of areas (15,16); they therefore cannot systematically represent these branchings, and so remain inaccurate as a basis for computing wire costs. Is optimization still discernable through so many barriers?…”