Neuroscience and Behavioral Physiology, Vol. 27, No. 4, 1997 DYNAMIC CHARACTER AND AGE DEPENDENCE OF FUNCTIONAL BRAIN ORGANIZATION IN ATTENTION N. V. Dubrovinskaya, R. I. Machinskaya, and Yu. V. Kulakovsky Intrahemispheric functional organization was studied during a task expectancy period with special reference to attention mechanisms. The estimation of coherence of functionally identical rhythmic EEG components was made to characterize the intracortical integration. Several factors influencing the possibility to make an adequate prognosis and to realize it were varied. Different types of the task (objective factor) were used. Subjects of different ages (7, 9-10 years, young adults) and children of the same age differing by the brain maturity level (subjective factor) were studied. It was shown that all factors studied have a certain influence on the brain organization underlying the task preceding attention. Clear age differences as well as the lag between the possibility to formation and realization of the prognosis in children were observed. Alternative "strategies" used in different ages to facilitate the task performance were analyzed; the underlying mechanisms were discussed. The ontogenetic development of information processing providing cognitive activity goes along with the possibilities of its modulation due to enhancing CNS plasticity. Modulatory influences originate from the brain activation system. Activation processes in accordance with the main ontogenetic trend acquire a controlled character and the possibility to modulate selectively the functional state of task-relevant cortical regions. The control function is exercised by the gradualIy maturing higher centers in the horizontal hierarchy [1, 3]. Selective controlled activation appearing as a result of situation analysis ensures [19] informational and mobilizational effects on current activity (selective attention), Attention controls all stages of nonautomated performance (real or mental). Special significance attaches to the anticipatory attention effects known as expectancy [22, 32] and priming [27, 28]. They appear as phasic events on the basis of tonic processes like a set [13, 34] and facilitate the forthcoming performance. At least two interacting processes are involved in the realization of facilitation effects of prestimulus attention, namely the formation of adequate prognosis of the situation (1) and the triggering, on this basis, of the activation mechanisms (2). A complicated dynamic brain organization is called for to realize the described processes. Its dependence on several factors is to be noted. The type of the task and the character of its presentation (repetition, interval stability, warning signal) facilitate the prediction possibility. The other group of factors includes the characteristics of the reactive system determined in our study by the age- and individual-dependent brain organization. All these factors may mediate both the formation of a model of the expected events and the realization of activation influences. According to these statements we carried out an electrophysiological study of brain organization underlying the task preceding attention directed to task performance by varying the above-mentioned factors. Two types of task were used differing by the complexity and prediction level (simple sensory/complicated verbal task). Subjects of different ages (children 7-8, 9-10 year old and adults) and children of the same age (7-8) with different brain maturity levels took part in the experiment. BRAIN ORGANIZATION OF ATrENTION DURING SENSORY TASK EXPECTANCY The task [22] consisted in intramodal binary classification of tactile and auditory stimuli according to their duration. Clicks were presented via earphones to the right (left) ear; tactile signals - through the vibrator to the right (left) index finger. Institute of Developmental Physiology, Russian Academy of Education, Moscow. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 47, No. 2, pp. 196-208, March-April, 1997. 0097-0549/97/2704-0427518.00 9 Plenum Publishing Corporation 427