The Role of the Neuronal Network in Functional Evolution of the Mammalian Telencephalon

During evolution of the vertebrate telencephalon the analyzing-synthesizing function was divided between two structures: the screen one, optimal for mechanisms of discrete analysis of information, and the neuronal network, in which cortical, functionally specialized modules can create the generalized equivalent of their activity. In the screen and reticular structures, each of these mechanisms got a possibility of developing independently without restricting functional capabilities of the other one. This resulted in formation of two telencephalon structures developing in parallel and functionally related, the cortex and the neostriatum. Experimental data indicate that the neuronal network of neostriatum is a field for interaction of corticofugal signals. These signals form neuronal mosaics reflecting the dynamics of cortical activity as combination patterns. Thereby, in neostriatum, corticofugal signals spread over a large surface of the cortex are transformed into their three-dimensional equivalent similar to population coding of information that takes place in the brain sensory structures. The established system of interrelationships between the cortex and the neostriatum turned out to be rather universal and economic. As a result, a broad spectrum of functional brain capabilities that we can see in various representatives of mammals was formed during a relatively short time with the minimum of structural changes, mainly quantitative in character.[PUBLICATION ABSTRACT]