Location of the dipoles of the P1 wave of visual evoked potential in the human brain

Autor: N.V. Anisimov, E. S. Mikhailova, V. A. Konyshev, I. A. Shevelev, A. V. Slavutskaya, Yu. A. Pirogov
Rok vydání: 2006
Předmět:
Zdroj: Doklady Biological Sciences. 409:285-289
ISSN: 1608-3105
0012-4966
DOI: 10.1134/s0012496606040041
Popis: Line fragments and their intersections are the basic properties of most objects in the visual world [3]; therefore, their rapid and reliable detection is important for image recognition. It is obvious that identification of lines (properties of the first order) and their intersections (properties of the second order) in images occurs in cats and monkeys already in the primary visual cortex where half of neurons detect the orientation of single lines and the other half of neurons more rapidly and strongly respond to their intersections or branching nodes [11, 12]. There is no information on the location of the mechanism responsible for identifying lines and their intersections in the human brain. Our previous study [1] demonstrated differences in the temporal and amplitude characteristics and regional specificity of the components of visual evoked potentials (EPs) in the human brain after presentation of images consisting of lines and crosses. However, the location of the dipole sources of these EP components has not been studied. Nevertheless, such information is important for assessing more precisely the involvement of different zones of the visual cortex in the identification of image properties. Therefore, we studied threedimensional location of dipole sources of the early component of visual EPs (wave P1) in the spherical and real model of the head in 12 subjects during presentation of images consisting of lines and crosses. The P1 component was selected because, first, it is associated with early stages of the processing of simple image features in the visual cortex, and, second, according to fMRT data, the location of the current dipole of the P1 wave coincides with the activation focus in the visual cortex [4]. METHODS The EEG was recorded in the electrophysiological experiments on 12 healthy subjects using a NeocortexPro 40-channel recording system (Neurobotics, Russia) according to the 10‐10 scheme with a sampling rate of 1000 Hz/channel. The right-ear electrode was used as an indifferent electrode. The upper limit of the frequency band of amplifiers was 100 Hz, the lower limit was 0.1 Hz, and the characteristic slope was 12 dB/octave. The subjects studied sat in a chamber isolated from light with a background illumination of 6 cd/m 2 . The images containing sets of lines or crosslike figures were shown for 100 ms on a monitor in a random order with various intervals [1]. The angular size of the image was 18.8° , and the size of its single element (cross or line) was 0.6° . Each experiment included 50 stimuli of each type. The average optical densities of the stimuli were equalized. A short sound warning was given 1 s before the beginning of the stimulus exposition. The subject focused the gaze at the fixation point in the screen center after the signal and watched the appearing image.
Databáze: OpenAIRE
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