[Brain activity during language processing]

The neural system, responsible for language comprehension, must quickly process and integrate a large amount of heterogenous linguistic data. There is no appropriate and generally acceptable description of the architecture of this system. This means that no model of language processing is available that will allow, without problems, to interpret the wide range of disorders of language functions in neurological patients with focal lesions and explain the no less inconsistent results of experiments dealing with various aspects of language processing both in healthy people and in patients. In this paper are summed up the main findings from works of several authors who with electrophysiological recording techniques and metabolic imaging techniques (PET and MRI) sought answers to the question "where" and "how" in the brain are processed open class words and closed class words, nouns and verbs, or perhaps what is the temporal co-ordination and laterality of semantic and syntactic processes in language processing. The frequent contradictions in the findings, which a reader may quickly discover, are probably due to the design of the experiment, the properties of the stimulus applied, the type of the task to be solved during the experiment by its participants. In patients it may be also due to the accuracy of the determination of the anatomical localization and the extent of the lesions in nervous structures. In this context, however, it is necessary to be reminded that applied methods have their strong as well as weak points. Metabolic imaging techniques reliably inform of the exact localization of metabolically active brain structures, but they only give a rough picture of temporal dynamics of brain processes. On the other hand, electrophysiological techniques reflect precisely the temporal dynamics of neuronal activation near the recording electrode, but they say little about the activity of neuronal assemblies in areas remote from the site of registration.