Visual evoked cortical potential (VECP) elicited by sinusoidal gratings controlled by pseudo-random stimulation. 2013

Carolina S Araújo, and Givago S Souza, and Bruno D Gomes, and Luiz Carlos L Silveira
Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil.

The contributions of contrast detection mechanisms to the visual cortical evoked potential (VECP) have been investigated studying the contrast-response and spatial frequency-response functions. Previously, the use of m-sequences for stimulus control has been almost restricted to multifocal electrophysiology stimulation and, in some aspects, it substantially differs from conventional VECPs. Single stimulation with spatial contrast temporally controlled by m-sequences has not been extensively tested or compared to multifocal techniques. Our purpose was to evaluate the influence of spatial frequency and contrast of sinusoidal gratings on the VECP elicited by pseudo-random stimulation. Nine normal subjects were stimulated by achromatic sinusoidal gratings driven by pseudo random binary m-sequence at seven spatial frequencies (0.4-10 cpd) and three stimulus sizes (4°, 8°, and 16° of visual angle). At 8° subtence, six contrast levels were used (3.12-99%). The first order kernel (K1) did not provide a consistent measurable signal across spatial frequencies and contrasts that were tested-signal was very small or absent-while the second order kernel first (K2.1) and second (K2.2) slices exhibited reliable responses for the stimulus range. The main differences between results obtained with the K2.1 and K2.2 were in the contrast gain as measured in the amplitude versus contrast and amplitude versus spatial frequency functions. The results indicated that K2.1 was dominated by M-pathway, but for some stimulus condition some P-pathway contribution could be found, while the second slice reflected the P-pathway contribution. The present work extended previous findings of the visual pathways contribution to VECP elicited by pseudorandom stimulation for a wider range of spatial frequencies.

UI MeSH Term Description Entries
D008297 Male Males
D010775 Photic Stimulation Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity. Stimulation, Photic,Visual Stimulation,Photic Stimulations,Stimulation, Visual,Stimulations, Photic,Stimulations, Visual,Visual Stimulations
D004594 Electrophysiology The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D005074 Evoked Potentials, Visual The electric response evoked in the cerebral cortex by visual stimulation or stimulation of the visual pathways. Visual Evoked Response,Evoked Potential, Visual,Evoked Response, Visual,Evoked Responses, Visual,Potential, Visual Evoked,Potentials, Visual Evoked,Response, Visual Evoked,Responses, Visual Evoked,Visual Evoked Potential,Visual Evoked Potentials,Visual Evoked Responses
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D014792 Visual Acuity Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast. Acuities, Visual,Acuity, Visual,Visual Acuities
D014795 Visual Pathways Set of cell bodies and nerve fibers conducting impulses from the eyes to the cerebral cortex. It includes the RETINA; OPTIC NERVE; optic tract; and geniculocalcarine tract. Pathway, Visual,Pathways, Visual,Visual Pathway
D055815 Young Adult A person between 19 and 24 years of age. Adult, Young,Adults, Young,Young Adults

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