Theoretical aspects of neuroplasticity

The authors propose an integrative theory of the organization of neuroplast ic processes. Neuroplasticity is assumed to be one of the essential charact eristics of the nervous tissue which may be manifested comparatively rapidl y and result in reversible changes (functional plasticity). It may also mod ulate the expression of genotype into phenotype (adaptation) and thus bring about long-lasting effects. Neuroplastic mechanisms are triggered by vario us natural or artificial stimuli, which may arise in the internal or extern al environment, and they may differ quantitatively or qualitatively. The ef fects of plasticity can lead to either positive or negative changes during development (evolutionary plasticity), after short-term exposition (reactiv e plasticity), after long-term or continuous stimuli (adaptational plastici ty), and during functional or structural recovery of damaged neuronal circu its (reparation plasticity). Manifestations of plasticity have probably the same basis, irrespective of the cause which triggered them or the brain re gion where they were accomplished. Neuroplastic mechanisms are based on the modulation of signal transmission across synapses. They can be related to interneuronal relations. The resulting changes may occur in the communicati on between neurons (synaptic level), in the activity of local neuronal circ uits (at the level of local circuits) or in the relations between individua l functional brain systems (multimodular level).