ABSTRACT
The ontogenetic development of information processing, which forms the basis of cognitive activity, changes along with the possibilities of modulation of such processing, arising from enhanced CNS plasticity. Modulatory influences originate from the activating system of the brain. As part of the main ontogenetic trend, activation processes acquire control functions, and the ability to selectively modulate the functional state of task-relevant cortical regions. The controlling function is exercised by gradual maturation of the executive centres in the anterior associative areas (frontal lobes) (Beteleva et al., 1977; Farber and Njiokiktjien, 1993). Selectively-controlled activation, appearing as a result of analysis of the prevailing situation ensures informational and mobilizing effects on current brain activity (i.e. selective attention) (Machinskaya and Dubrovinskaya, 1994). Attention controls all stages of non-automated performance (real or mental). However, anticipatory attention involved in expectancy (Machinskii et al., 1988; Tecce, 1972) or priming (Posner et al., 1989; Sheppard and Boyer, 1990) acquires special significance. At least two interacting processes should be involved in producing facilitatory effects for such prestimulus attention. These are: (1) the formation of an adequate prediction of the situation, and (2) triggering of the appropriate mechanisms of activation, on
the basis of such a prediction. A complicated organization of brain dynamics is needed to realize these processes. This depends on several important factors: Depending on the type of task and the mode of its presentation (repetition, interval stability, warning signal) prediction may be facilitated. The other group of factors includes parameters of the reactive system, determined (in our study) by brain organization dependent on age and individual characteristics. All these factors may mediate both the formation of a model of expected events, and the actual production of activation influences.
