140 Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205

who, on the contrary, are predominantly right-handed. The type of visualasymmetry did not render any significant influence on the size of this illusion.

By amount of visual–spatial intelligence two groups of examinees wererevealed. For the group of examinees with average and high IQ, an inverserelationship between the size of the distortion and visual–spatial abilitiestook place.

The ERPs were registered by presentation of a set of isomorphicPoggendorff figures in women who were right-handed. It was establishedthat visual P100 answer for figures causing the illusion was much more incomparisonwith the control figure. In addition, an occurrence of N170 wave insymmetric parietal, occipital and parietal areas was revealed. The amplitudeof visual N170 answer to the illusory stimulus was distinctly less. The datareceived specify that the visual distortion of an arrangement of elements ofthe Poggendorff figure arises at an earlier stage of information processingthan was previously considered to be the case.

Supported by the Siberian Federal University and Krasnoyarsk StatePedagogical University.

doi:10.1016/j.ijpsycho.2008.05.339

EEG and EYE tracking for visual search task investigation in humans

A.V. Latanova, N.S. Konovalovaa, A.A. Yermachenkob

a MV Lomonosov State University, Department of Neurobiology, Moscow, Russiab Modern University for the Humanities, Institute of Cognitive Neuroscience,Moscow, Russia

Nowadays eye movements (EM) are usually recorded by the video eyetracking (ET) technology. It iswidely used for EMpattern analyses duringperusalof complex image, but it is seldom done simultaneously with EEG recording.Some electrophysiological parameters (EEG, ECG, GSR) are traditionallyconsidered to indicate processes, related to solving visual tasks. We studiedthe EEG correlates of finding a relevant stimulus (RS) among irrelevant stimuli(IS) during the visual search task performance. By means of precise EEG and ETsynchronization we marked out the short EEG fragments concurrent with themoment of finding the RS and analyzed them. The experiments were held over15 volunteers without neurological history. 100 images with about fiftynonverbal stimuli were exposed to each subject. The task consisted of findingthe RS and fixing the gaze on it for a couple of seconds. There were 45–57 IS oneach image and one RS with a pseudorandomly varied position. The differencebetween two stimuli types was not too hard to detect (all subjects managed tofind the proper stimulus on each picture), and at the same time it was not toosimple (it seldom took the subjects less than a second to find the key stimulus).The differences among ISwere in rotation angle, position and size, but theywerealways of the same shape. The EEG was recorded over О1, О2, Р3, Р4, С3, С4, F3,F4 leads.We also recorded the EOG,whichwasused for determining the saccademoving the eyes towards the RS. The gaze fixation on RS was verified by ET. Weshowed that theRSfinding induces anevent-relateddesynchronization (ERD) inalpha band (8–12 Hz). RS finding causes the 1,5–2 times decrease in EEGamplitude in comparison with searching process. ERD was best exposed inoccipital and parietal leads. We conclude that solving the visual search taskinduces changes in human functional condition like top-down attention andrecognition, which are partly indicated by ERD. Further researchmay result in adetermining object's visual features, evoking changes in human status. Theproject is supported by RFBR grant (№ 06-04-48166).

doi:10.1016/j.ijpsycho.2008.05.340

Invariant visual-recognition learning in monkey: Effect of hemisphericspecialization of the prefrontal cortex

K.N. Dudkin, I.V. Chueva, F.N. MakarovPavlov Institute of Physiology, Russian Academy of Sciences, St Petersburg, Russia

Conditioned behavior includes visual recognition as one of the basicstages, its function — the best current interpretation and understanding ofvisual scenes and objects. Storing of the information necessary for it isrealized by means of learning and is connected with two aspects of long-termmemory: with forming, storage and reproduction cognitive structures andwith selective increase in their biological significance. The prefrontal cortexplays the important role in the visual recognition processing. To understand apossible mechanism of hemispheric specialization of the prefrontal cortex for

invariant visual-recognition we studied learning processes involving visualdiscrimination of stimuli with different visual attributes on three groups ofrhesus monkeys.

The left and the right prefrontal cortices sulcus principalis were removedin monkeys of the first and of the second groups, accordingly. The remainingintact animals served as control. The monkeys were tested for invariantrecognition after complete training to visual discrimination and after stimulitransformations (variation in size, shape, orientation and spatial relation-ships). Monkey's correct decisions, refusals of task decision and motorreaction time were recorded. The results obtained demonstrate “transfer oftraining” after transformations of conditioned stimuli in monkeys of controlgroup. The invariance of recognition is provided due to the presence of thecommon sensory properties of visual objects, which are selected duringsensory processing and are retained after transformations. It means, thatvisual discrimination learning processes form in long-term memory certaindemarcating features representing cognitive structures providing recognitionand classification of visual objects.

As compared with control monkeys, after removal of left and rightprefrontal cortices sulcus principalis learning processes became unstable fordiscrimination of all stimuli, and as a result the training periods weresignificantly lengthened, especially for spatial information. The transforma-tion of stimuli involving nonspatial information: geometrical figures ofvarious shape, size and orientation did not influence correct decisions thoughrefusals of decision and reaction time were increased. The invariance of thisdiscrimination was achieved. However, the invariance for discrimination ofstimuli connected with spatial information after transformation was notachieved only in monkeys after removal of left prefrontal cortex sulcusprincipalis. These results indicate that left (but not right) prefrontal cortexsulcus principalis takes part in invariant visual-recognition by formingdemarcating features and providing spatial-information processing. It isclear, that invariance of nonspatial information recognition is provided byother cortical areas, first of all, the inferotemporal cortex.

doi:10.1016/j.ijpsycho.2008.05.341

Visual attention modulates the frontal eye field executive functions:Electrophysiological correlates

F. Jaglaa, M. Jergelovaba Institute of Normal and Pathological Physiology, Slovak Academy of Sciences,Laboratory of Cognitive Neuroscience, Bratislava, Slovakiab Laboratory of Cognitive Neuroscience, Institute of Normal and PathologicalPhysiology, Slovak Academy of Sciences, Bratislava, Slovakia

Several areas in frontal, temporal and parietal human cortices have beenidentified as functionally important not only in programming and executionof saccadic eye movements but in attentional control of processing visualinformation as well. Their functional role in the oculomotor controlmechanisms was described in numerous studies. However, how these areasinteract to form dynamic attentional networks which control the focusing ofvisual attention in humans is not yet fully understood. Some insight into theproblem, especially for timing, can offer the analysis of evoked potentials timelocked to the onset of saccades (SEMRPs) registered simultaneously over thefrontal and parietal eye fields. Contrarily to parietal components the frontalones are not so particularly described in humans. The study presents theelectrophysiological data that during the primary encoding the basic spaceand shape characteristics of new visual stimuli, as revealed by prominentlambda complex over the posterior eye fields, a markedly decreased activity isto be registered over the frontal eye fields. It is reflected as a prominent sharpwave peaking at the time of the lambda response. The hypothesis wasproposed that this decreased activity may be assumed as a correlate ofblocking the frontal eye field executive functions which protects new visualinformation encoding from disturbance introduced by triggering new eyemovement. Different attenuation of frontal SEMRPs in condition of dividedvisual attention task, revealed by laterally different attenuation of the frontalsharp wave, correlates with the functional asymmetry of brain hemispheresas well as with their role in programming and generation of saccades. Thesefindings support the proposed hypothesis as also association betweenprogramming the direction of saccadic eye movement and shifting the visualattention into the particular region of the visual field. The analysis of theSEMRPs elicited by simple visual targets in selectedmental disorders revealedalso that the frontal potential changes aremore sensitive to various functional