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Twelve healthy subjects underwent investigation of averaged (electroencephalogram) EEG potentials during preparation for motor activity and in the latent period (LP) of visually evoked saccades by presentation of stimuli using Posner's (1980) design of "cost-benefit." It has been shown that covert spatial attention orientation leads to an increase in amplitude and decrease in latency of presaccadic initiation potential peaks within the saccadic latent period (LP) (P-100, N -50). Processes of covert orientation of attention during the interstimulus interval period of anticipation of the target stimulus correlate with the increase of slow negativity of fronto-parietal-temporal localization. Spatial-temporal changes of presaccadic potentials are evidence of the fact that orientation of attention during motor preparation and saccadic initiation is reflected in intensification of fronto-parietal networks of saccadic control and attention, activating the fronto-medio-thalamic and thalamo-parietal modulating systems. Keywords: orienting of attention, saccades, latent period, presaccadic potentialsSe examinaron los potenciales EEG promediados de doce sujetos sanos durante su preparación para actividad motor y en el período latente de sacádicos evocados visualmente por la presentación de estímulos según el diseño de "coste-beneficio" de Posner (1980). Se ha mostrado que la orientación de la atención espacial encubierto lleva a un incremento en la amplitud y un decremento en la latencia de los picos potenciales de iniciación presacádica dentro del período sacádico latente (P-100, N -50). Los procesos encubiertos de orientación de la atención durante el período del intervalo inter-estímulo de anticipación del estímulo meta correlacionan con el incremento de la negatividad lenta de localización fronto-parietal. Cambios espacio-temporales de potenciales presacádicos son evidencia del hecho de que la orientación de la atención durante la preparación motora y la iniciación sacádica se refleja en la intensificación de las redes fronto-parietales de control y atención, activando los sistemas de modulación

Numerous psychophysiological and neurophysiological studies focus on saccadic eye movement in humans. Saccades are regarded as an adequate model for studying not only visual perception and attention, but also the central mechanisms of behavior control. The cortical mechanisms of saccadic generation are reflected in the electric potentials of the human brain [1][2][3][4][5][6].Two main types of saccades are distinguished in published studies: (1) those performed in response to a visual stimulus and (2) voluntary ones. It is assumed that the integration of visual spatial attention and the corresponding motor command is necessary for type 1 saccades, whereas the performance of voluntary saccades, e.g., antisaccades, entails strict requirements for the activities of higher oculomotor centers, mainly the prefrontal cortex [7,8].Many neurological and psychiatric diseases are accompanied by disturbances in vision fixation and eye movements. Specific disturbances in the oculomotor function carry important information for the identification of the damaged cerebral regions [7,8].Specific disturbances in saccadic eye movements are always found in schizophrenics and their relatives [7][8][9]. However, their origin and precise location of the pathology remain largely unknown.Studies on the parameters of voluntary saccades in schizophrenics with the use of the antisaccadic paradigm repeatedly demonstrated a considerable increase in the percentage of incorrect answers and in the latency of correct answers [7][8][9]. Studying slow negative presaccadic potentials in the test with antisaccades showed that their amplitude in the frontocentral region is substantially decreased, which indicates that schizophrenia is accompanied by frontal dysfunction [2, 10].The central mechanisms of the preparation of saccade in response to visual stimuli in schizophrenia were studied considerably less. Some researchers did not find disturbances in the characteristics of saccades in schizophrenics, whereas others observed an increase in the number of saccades with a short latency, which are called express saccades [7,11]. The cortical potentials preceding the performance of saccades in response to visual stimuli have not been studied. However, such studies are expected to yield valuable results, because pathomorphological and functional tomographic data indicate that schizophrenia affects not only the prefrontal cortex but also many other cerebral structures involved in the control of eye movements (the cerebellum, ventral striatum, midbrain, etc.) [12][13][14].The purpose of this study was to analyze the parameters of the saccades performed in response to visual stimuli and the preceding slow potentials in schizophrenics.Abstract -The parameters of saccades and presaccadic slow potentials were studied in right-handed men with a dominant right eye, including 19 schizophrenics and 12 healthy subjects. For visual stimulation, three lightemitting diodes were used, which were located in the center of the visual field (the central fixation stimulus) and ...

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