[Modification of evoked potentials by increasing visual search difficulty in humans]

Monopolar evoked potentials on increasing difficulty of the task of visual search in frontal, parietal, temporal and occipital regions was studied in 16 young healthy subjects. Search complication and adding noise in the form of visual stimulus hindered recognition of images that affected search time and errors amount. Correlation between evoked potential magnitude and parameters of the search generally observed in frontal region: a significant positive one between N2, P4 components; between SN-SP difference waves and task difficulty: a negative one between P3 and N2 components. Amplitudes of N2 and P4 components were mostly expressed in frontal lobe. It was supposed that the data obtained indicated dominance of the frontal structures in the attention system during increasing the difficulty of the task.