The high density EEG was registered in 41 healthy subjects (20 males, 21 females) in the cardinal (horizontal and vertical) and oblique (45 and 135 deg) line orientation identification task. The analysis of the adaptive amplitude maximum (4 ms averaging) of P1 and N1 evoked potentials in the symmetrical occipital, parietal and inferior temporal areas and dipole source modelling showed the anisotropy of cortical responses in the 80-150 ms interval. The amplitude is higher on the oblique orientations as comparison with cardinal ones. The temporal and regional features of cortical answers were discovered. The earlier selective response (~90 ms latency) is registered.in the parietal areas, while the later (~145 ms latency) is found in the occipital ones. We discovered a number of sex-related differences in the early stages of line orientation detection. In males, the amplitude of components is higher; they have broader area of localisation of their dipole sources: in addition to the occipital and parietal regions, cortex of the temporal regions is involved. Theobtained data are discussed in the context of the idea of effective neural coding (Barlow, 1959) and the features of spatial information processing in the visual system of males and females.