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      The effect of spectral filters on VEP and alpha-wave responses Translated title: Efecto de los filtros espectrales sobre el PVE y las respuestas de las ondas alfa

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          Abstract

          Purpose

          Spectral filters are used to treat light sensitivity in individuals with traumatic brain injury (TBI); however, the effect of these filters on normal visual function has not been elucidated. Thus, the current study aimed to determine the effect of spectral filters on objectively-measured visual-evoked potential (VEP) and alpha-wave responses in the visually-normal population.

          Methods

          The full-field (15°H × 17°V), pattern-reversal VEP (20′ check size, mean luminance 52 cd/m 2) was administered to 20 visually-normal individuals. They were tested with four Intuitive-Colorimeter-derived, broad-band, spectral filters (i.e., gray/neutral density, blue, yellow, and red), which produced similar luminance values for the test stimulus. The VEP N75 and P100 latencies, and VEP amplitude, were recorded. Power spectrum analysis was used to derive the respective powers at each frequency, and peak frequency, for the selected 9–11 Hz components of the alpha band.

          Results

          Both N75 and P100 latencies increased with the addition of each filter when compared to baseline. Additionally, each filter numerically reduced intra-session amplitude variability relative to baseline. There were no significant effects on either the mean VEP amplitude or alpha wave parameters.

          Conclusions

          The Intuitive Colorimeter filters significantly increased both N75 and P100 latencies, an effect which is primarily attributable (∼75%) to luminance, and in some cases, specific spectral effects (e.g., blue and red). VEP amplitude and alpha power were not significantly affected. These findings provide an important reference to which either amplitude or power changes in light-sensitive, younger clinical groups can be compared.

          Resumen

          Objetivo

          Los filtros espectrales se utilizan para tratar la sensibilidad a la luz en individuos con lesión cerebral traumática (TBI); sin embargo, no se ha esclarecido el efecto de estos filtros sobre la función visual normal. Por ello, el estudio actual trató de determinar el efecto de los filtros espectrales sobre el potencial evocado visual (PVE) y las respuestas de las ondas alfa, medido objetivamente en la población con visión normal.

          Métodos

          Se aplicó un PVE de campo completo (15°H × 17°V), y patrón invertido (tamaño de estímulo de 20’, y luminancia media de 52 cd/m 2) a veinte individuos con visión normal. Se realizó la prueba utilizando cuatro filtros espectrales de banda ancha, derivados del Colorímetro Intuitivo (densidad gris/neutra, azul, amarillo y rojo), que produjeron unos valores de luminancia similares para los estímulos de la prueba. Se registraron las latencias N75 y P100, y la amplitud del PVE. Se utilizó el análisis del espectro de potencia para calcular las respectivas potencias en cada frecuencia, así como la frecuencia máxima, para los componentes seleccionados de 9–11 Hz de la banda alfa.

          Resultados

          Ambas latencias N75 y P100 se incrementaron con la incorporación de cada filtro, en comparación a la línea basal. Además, cada filtro redujo numéricamente la variabilidad de la amplitud intra-sesión, en relación a la línea basal. No se produjeron efectos significativos sobre la amplitud del PVE medio o los parámetros de la onda alfa.

          Conclusiones

          Los filtros del Colorímetro Intuitivo redujeron considerablemente las latencias N75 y P100, un efecto que es principalmente atribuible a la luminancia (∼75%), y en algunos casos a los efectos espectrales específicos (es decir, el azul y el rojo). La amplitud del PVE y la potencia alfa no se vieron significativamente afectados. Estos hallazgos aportan una importante referencia para poder comparar tanto los cambios de amplitud como de potencia en los grupos clínicos de personas más jóvenes, con sensibilidad a la luz.

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          Most cited references22

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          EEG alpha and theta oscillations reflect cognitive and memory performance: a review and analysis.

          Evidence is presented that EEG oscillations in the alpha and theta band reflect cognitive and memory performance in particular. Good performance is related to two types of EEG phenomena (i) a tonic increase in alpha but a decrease in theta power, and (ii) a large phasic (event-related) decrease in alpha but increase in theta, depending on the type of memory demands. Because alpha frequency shows large interindividual differences which are related to age and memory performance, this double dissociation between alpha vs. theta and tonic vs. phasic changes can be observed only if fixed frequency bands are abandoned. It is suggested to adjust the frequency windows of alpha and theta for each subject by using individual alpha frequency as an anchor point. Based on this procedure, a consistent interpretation of a variety of findings is made possible. As an example, in a similar way as brain volume does, upper alpha power increases (but theta power decreases) from early childhood to adulthood, whereas the opposite holds true for the late part of the lifespan. Alpha power is lowered and theta power enhanced in subjects with a variety of different neurological disorders. Furthermore, after sustained wakefulness and during the transition from waking to sleeping when the ability to respond to external stimuli ceases, upper alpha power decreases, whereas theta increases. Event-related changes indicate that the extent of upper alpha desynchronization is positively correlated with (semantic) long-term memory performance, whereas theta synchronization is positively correlated with the ability to encode new information. The reviewed findings are interpreted on the basis of brain oscillations. It is suggested that the encoding of new information is reflected by theta oscillations in hippocampo-cortical feedback loops, whereas search and retrieval processes in (semantic) long-term memory are reflected by upper alpha oscillations in thalamo-cortical feedback loops. Copyright 1999 Elsevier Science B.V.
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            ISCEV standard for clinical visual evoked potentials (2009 update).

            Visual evoked potentials (VEPs) can provide important diagnostic information regarding the functional integrity of the visual system. This document updates the ISCEV standard for clinical VEP testing and supersedes the 2004 standard. The major change in this revision is that test parameters have been made more precise to achieve better consistency of results within and between test centers. The ISCEV standard VEP protocols are defined for a single recording channel with a midline occipital active electrode. These protocols are intended for assessment of prechiasmal function; additional electrode sites are recommended for evaluation of chiasmal and postchiasmal function. ISCEV has selected a subset of stimulus and recording conditions that provide core clinical information and can be performed by most clinical electrophysiology laboratories throughout the world. These are: 1. Pattern-reversal VEPs elicited by checkerboard stimuli with large 1 degrees (i.e., 60 min of arc; min) and small 0.25 degrees (15 min) checks. 2. Pattern onset/offset VEPs elicited by checkerboard stimuli with large 1 degrees (60 min) and small 0.25 degrees (15 min) checks. 3. Flash VEP elicited by a brief luminance increment, a flash, which subtends a visual field of at least 20 degrees.
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              The spatial transformation of color in the primary visual cortex of the macaque monkey.

              Perceptually, color is used to discriminate objects by hue and to identify color boundaries. The primate retina and the lateral geniculate nucleus (LGN) have cell populations sensitive to color modulation, but the role of the primary visual cortex (V1) in color signal processing is uncertain. We re-evaluated color processing in V1 by studying single-neuron responses to luminance and to equiluminant color patterns equated for cone contrast. Many neurons respond robustly to both equiluminant color and luminance modulation (color-luminance cells). Also, there are neurons that prefer luminance (luminance cells), and a few neurons that prefer color (color cells). Surprisingly, most color-luminance cells are spatial-frequency tuned, with approximately equal selectivity for chromatic and achromatic patterns. Therefore, V1 retains the color sensitivity provided by the LGN, and adds spatial selectivity for color boundaries.
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                Author and article information

                Contributors
                Journal
                J Optom
                J Optom
                Journal of Optometry
                Elsevier
                1888-4296
                1989-1342
                17 August 2015
                Apr-Jun 2016
                17 August 2015
                : 9
                : 2
                : 110-117
                Affiliations
                [0005]Department of Biological and Vision Sciences, SUNY State College of Optometry, 33 West 42nd Street, New York, NY 10036, United States
                Author notes
                [* ]Corresponding author. kwilleford@ 123456sunyopt.edu
                Article
                S1888-4296(15)00060-6
                10.1016/j.optom.2015.07.003
                4812008
                26293969
                ac891d26-597e-4aa9-bc1b-f4e92507534a
                © 2015 Spanish General Council of Optometry. Published by Elsevier España, S.L.U.

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 31 March 2015
                : 4 July 2015
                Categories
                Original Article

                visual-evoked potential (vep),electrophysiology,brain injury,intuitive colorimeter,colored filters,potencial evocado visual (pev),filtro espectral,color,electrofisiología,corteza visual,lesión cerebral,colorímetro intuitivo,filtros coloreados

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