ИСТИНА

When oculomotor system selects a stimulus as a saccadic target there is a simultaneous inhibition of other possible responses, irrelevant for the current behavior. The cognitive processes of attention and decision-making play an active role in the saccade programming. The aim of our research was to analyse spatial-temporal parameters of saccades and presaccadic ERP-potentials at the simultaneous presentation of the target and distracting stimuli to the leading and unleading eye. 15 healthy right-handed volunteers participated in the study. Target and distracting peripheral visual stimuli were presented monocularly on the monitor in various spatial combinations. Eye movements were recorded using the EOG. The LP of correct saccades increased when the target and distracting stimuli were presented in the different visual hemifields at the distance 15-20 dergees and were minimal when the stimuli were presented at the same hemifield at the distance 5 degrees. At the same time the number of erroneous saccades was the biggest. More often error was a saccade to the distracting stimulus the first and to the target one the next. Such incorrect saccades appeared when LP saccades decreased by 50-60 ms compared to the LP of correct saccades (p <0.05). The complex of the positive and negative potentials was revealed in the saccade latent period. Latency of all components was shorter upon presentation of stimuli to the left, unleading eye, that may indicate the earlier saccade preparation. At the same time LP saccades were longer in this conditions (p<0.05). The results show that early potentials N1 and P1 were higer in amplitude and dominated in the controlateral parietal-occipital areas. It can be reflection of visual sensory processing. The amplitude of the later negative potential N2 at the stimulation of the right eye increased in the case when target stimulus was at the same location than at the previous realisation. At the backward averaging of EEG from the saccade beginning premotor potentials have been obtained and analyzed. Potential N-1 immediately preceding the beginning of saccade and associated with activation of neurons in the contralateral oculomotor fields in the parietal cortex (LIP and 7a). This study found the fact of changing the localization of N-1 potential. It had a maximum amplitude and dominated in the frontal eye fields contralateral to the hemifield where the distracting stimulus were located. Such localization of N-1 foci may be associated with an active inhibition of leading oculomotor fields of frontal cortex in case of avoid the saccade initiation to irrelevant stimulus.