Aspects of neural plasticity in the central nervous system-VII. Theoretical aspects of brain communication and computation.

Some aspects of the communicational and computational features of the central nervous system are discussed. The existence in the central nervous system of two main types of interneuronal communication, the wiring (i.e. the classical type of synaptic transmission) and the volume (i.e. a humoral type of non-synaptic transmission) transmission, has been proposed. Some features of these types of transmission are discussed, with special reference to the informational properties of peptide transmitters. With respect to the computational aspects of neural function, the identification of putative computational structures at the macroscopic (network) and microscopic (local circuit, synapse) levels suggests the existence of a computational hierarchical organization. In this context, the existence of a compartmental organization of various cerebral regions is discussed. It is hypothesized that membrane domains, made by patches of membrane in which preselected molecular movements are possible resulting in molecular interactions, can have an important role in the integrative capabilities of neural tissue. The coexistence of multiple neuroactive substances in central synapses is analyzed in the framework of information transfer processes at this level. The presence of putative homeostatic, heterostatic and mnestic mechanisms in the synapse is also discussed.