Title : Investigation of brain systems: from activations to interactions
Currently, the so-called activation studies are the dominant approach to investigate the functional organization of the brain. Within the framework of these studies, the functional specialization of certain brain structures with respect to the types of activity under investigation is judged by their energy state. More often, an increase in local neuronal activity is considered as evidence of the involvement of brain structures in maintaining ongoing activities. However, the significant experimental material accumulated to date indicates the unproductive nature of this approach. And although for each function or mechanism it is possible to define a set of brain structures that are reproducibly involved in their maintenance, it is still unclear how exactly these structures work and whether their sets can be considered as specialized brain systems. Activation studies do not take into account the known properties of brain systems, according to which any activity is provided by the combined work of distantly located links of neuronal systems. At the moment, methods have been created that make it possible to study the interactions and interrelationships between brain structures as the links of such systems that reflect the nature of their combined work. The studies carried out by us with functional magnetic resonance tomography have shown that the brain systems maintaining the current activities are significantly richer than it appears from the standpoint of activation studies. Namely, it was found that the brain systems are far from being limited to those links that show their participation in its work by changing the level of their neuronal activity. This radically changes our understanding of how brain systems are organized. For the further study of functional brain systems new methods are needed to analyze precisely the functional interactions between the involved structures of the brain.