V. V. Khrenkova - Senior Research Scientist, Southern Federal University (Rostov-on-Don). E-mail: vvkhrenkova@gmail.com
V. V. Zolotukhin - Senior Research Scientist, Southern Federal University (Rostov-on-Don). E-mail: zokhr_100@mail.ru
P. V. Zolotukhin - Post-graduate Student, Southern Federal University (Rostov-on-Don). E-mail: p.zolotukhin@gmail.com

Significant effort has been dedicated to the studying of the central mechanisms of attention. And yet, much remains unknown and inapproachable in human studies. Thus, electrophysiological studies in animals are of significant value for advancing in understanding of the neuronal mechanisms of different types of attention. Electrophysiological indices thought to represent attention are impulse activity of individual neurons, and focal potentials. The aim of the present investigation was to study the neurophysiological mechanisms of orienting reaction to diffuse and structured (squares of 12 angular degrees) stimuli of different colors in Rana ridibunda. Induced impulse activity (IA) and focal potentials (FP) were registered in three (superficial, medial and deep) symmetric functional layers of the frog-s mesencephalon. Each first stimulation induced orienting reaction (OR) characterized by relatively short latent potential, high response amplitude, high general activation level. General activation had been being observed for few seconds after the OR ending and was represented by spontaneous FP and IA. The expressiveness of OR depended on the direction of functional inter-hemisphere asymmetry, functional layer tested, color and shape of the stimulus, and inter-stimulation timing. Subsequent stimulations caused fading of OR and general activation being superseded with local activation. The latter, probably, represents selective attention towards the stimulus. Repetitive stimulation caused cycling recovery of OR (after 3-5 stimulus presentations), which was more pronounced in superficial layers of dominant visual lobe and with respect to structured stimuli. According to the results of the study, in poikilothermic animals, frog specifically, the mechanisms of orienting reaction and selective attention are provided by polyfunctional groups of neurons of the midbrain cortex. However, the mechanisms of the two attention types are spatially divergent through localization to different layers of the cortex: superficial projectional layers are mostly responsible for orienting reaction, while medial and deep layers provide selective reaction.