Navegando por Autor "MARTINS, Isabelle Christine Vieira da Silva"

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Efeitos da suplementação com açaí clarificado (Euterpe oleracea Mart.) sobre marcadores de estresse oxidativo em pacientes com doença renal crônica em hemodiálise
(Universidade Federal do Pará, 2019-06) MARTINS, Isabelle Christine Vieira da Silva; NASCIMENTO, José Luiz Martins do; http://lattes.cnpq.br/7216249286784978; https://orcid.org/0000-0003-3647-9124
Acesso aberto (Open Access)
Seletividade espacial de cor do potencial cortical provocado visual pseudoaleatório
(Universidade Federal do Pará, 2014-04-23) MARTINS, Isabelle Christine Vieira da Silva; SOUZA, Givago da Silva; http://lattes.cnpq.br/5705421011644718
Spatial selectivity to color stimulation has been investigated using invasive and non-invasive electrophysiological methods, and psychophysical methods. In non-invasive visual cortical electrophysiology, this issue was investigated using conventional methods of periodical stimulation; and averaging methods to extract responses. New methods of stimulation (pseudo-random presentation) and of signal extraction (cross-correlation) were developed and still lack their application to investigate the spatial selectivity of the cortical chromatic responses. The present study aimed to apply the new pseudo-random presentation electrophysiology method for study spatial selectivity of the color visual. Fourteen trichromats and 16 color-blind subjects were included in the sample. All the volunteers had normal or corrected visual acuity. They were evaluated by anomaloscopy HMC and Ishihara Plates test to be qualified the color vision in normal trichromacy or not. Sinusoidal gratings, 8º of visual angle, red-green contrast for 8 spatial frequencies among 0.2 a 10 cpd. The stimuli were temporally modulated by a binary m-sequence to simulate pattern reversal mode presentation. Veris system was used to extract the second order kernel, first and second slices (K2.1 e K2.2, respectively). After modeling of spatial frequencies response data with functions of difference of Gaussians, it was extracted the optimal spatial frequency and the bandwidth of spatial frequencies with amplitudes above of ¾ of the maximum amplitude of the spatial frequency-response function. Chromatic visual acuity also was estimated by the fit of a linear model to the amplitude data since from the optimal spatial frequency until the highest tested spatial frequency. In trichromats, the chromatic responses were found in the K2.1 and K2.2, whose showed different spatial selectivity. The negative components in the K2.1 and K2.2 showed band-pass tuning, and the positive component in the K2.1 showed low-pass tuning. The estimated chromatic visual acuity of the kernel components were comparable to those estimated by previous psychophysical studies. Different cellular components might contribute to the pseudo-random VECP generation. This new method is a potential candidate to an important tool for non-invasive evaluation of the human color vision.